Chpt 3-6 in David Caplan (1985). Neurolinguistics and Linguistic Aphasiology: an Introduction. Cambridge Univ. Press.

3

The discoverieso f Paul Broca:l ocalization of the "faculty for aticulate language"

The first scientifics tudies of patients with acquired disorderso f language were presentedi n the lasth alf of the nineteenthc entury.T hey beganw ith an addressb y Paul Broca before the Anthropological Societyo f Parisi n 1861. That presentationa nd Broca's work over the next four yearse stablisheda n approacht o aphasiaa nd neurolinguisticsw hich hasd ominatedt he field until recent years.W e therefore begin with this seminalb ody of work. Broca's 1861p resentationt ook placed uring an ongoingd ebatea bout the phrenologicalt heory of the localizationo f higherf unctionsi n the brain. The phrenologists- Gall, Sperzheim,a nd others - had claimed that the moral, intellectual,a nd spiritualf acultieso f man were eacht he resulto f the activity of particular portions of the brain, and that the size of the brain area responsiblef or a given ability determinedt he degreeo f developmento f that ability or faculty in an individual. The phrenologistsa lsoa rguedt hat the size of portions of the skull reflectedt he size of the underlying brain, and that they could predict the capacitieso f individualsb y palpatingt heir heads.T his they did, in popular and remunerative demonstrations. The scientific community of the mid-nineteenth century had mixed feelings about the phrenologicald octrine, and its fairly notoriousa nd lucrativep opularization and application, and by 1861m ost of its claimsh ad been refuted. The claim which remaineds omewhati ntact wast hat languagew asl ocated in the frontal lobes of the brain, in particular in the portion just above the eye socket (the supra-orbital portion). Bouillaud, an influential French physician, had published papers in 1830a nd 1848a rguing in favor of this localization. His son-in-law, Aubertin, a member of the Anthropological Society,w as aproponent of phrenologyi n general,a nd of his father-in-law's claim about languagei n particular. When Broca's attention was drawn to the first of his famous casesa t the Bic6tre hospital,h e recognizeda possible test caseo f the phrenologicald octrine with respectt o its best-established claim, that regarding language, and he invited Aubertin to examine the patient in question.A ubertin did so, and agreedt hat the patient shouldh ave a frontal lesion. In fact, Pierre Marie (1906b)l ater reported that Aubertin publicly said that he would reject Bouillaud's theory if Broca's patient did 1l Clinicel aphasiologv and neurolinguistics not have a frontal lesion. There was thus considerablei nterest in the case. As it happened,B roca'sp atiento nly lived three daysb eyondB roca'sa nd Aubertin's examination, and Broca was able to present the resultso f the autopsyt o the Anthropological Societyi mmediately. Broca'sp atient- Lebourgne- had beenh ospitalizedf or twenty-oney ears when he died at the ageo f fifty-seven.T he initial reasonf or his hospitaliza- tion was that he was almost mute - his only verbal output consistedo f the syllable" tan", and he becamek nown as" Tan" in the hospital.D espitet his severeh andicap, Lebourgne functioned independentlya t Bic0tre hospital. He apparently understood what was said to him. and was able to respond appropriatelya nd make his needsk nown. ln fact. he wasg enerallyk nown as a difficult character. After about ten years. Lebourgne's condition wor- sened:h e lostt he useo f hisr ight arm. Shortlyb eforeh isd eath,t hisp aralysis extendedt o the right leg as well,lcaving hinr bedridden.H e developeda n infectioni n the paralyzedle g,w hichb roughth im to Broca'sa ttention.V ery soon thercafter the infection led to generalizeds epsisa nd death. Brocae xaminedt he braini mmecliatelay ftert hea utopsy.A ccordingt o his report, the brain showed a lesion in thc left frontal lobe. thus confirming Bouillaud'sa nd Aubertin'st heorv.T he lesionc onsistedo fa cystl ocateda t the fclot

A A Thed iscoverieosf Paul Broca

Figure3 -1.T he braino f Lebourgnes howinga lesioni n Broca'sa rea (SourceM: outier 1908:7 6)

ability along two major lines: linguistic versus non-linguistic communica- tion; and receptive versus expressive abilities. Broca considered that Lebourgne had no deficit with non-linguistic communication or with recep- tive language,a s evidencedb y his apparenta bility to understandw hat was said to him and to interact with others. He therefore suggestedt hat Lebourgne had an isolated problem in what Broca termed the "faculty of articulatel anguage". This analysiso f languagei nto facultiesi s one which dominateda great deal of the work of the nineteenthc entury, and which we shalls eei n almost all the theorieso f the "connectionist" aphasiologists. The analysis of the neurological aspectso f this syndrome was more innovative than the psychologicala nalysis. Prior to Broca, it had been thought that the appropriate approach to localizing higher functions in the brain was to analyzel esionsi n terms of absoluted istancesf rom the major anatomicall andmarks of the brain or skull. It had been thought that there were no divisions smaller than the major lobes of the brain which were constantf rom one individual brain to another, and which could be the substrateso f psychologicalf unctions. Broca argued that the convolutional anatomyo f the brain was relatively constantf rom individual to individual, and that it was appropriate to look to convolutions as possible anatomical sites of localization of the higher functions. He specifically suggestedt hat much of the phrenological approach to localization was marred by its dependence on absolute measurements from major fissures and other landmarkso f the brain and skull, which, becauseo f the variation in the size of brains, could reflect different convolutional sites in different brains. He 45 II Clinical aphasiology and neurolinguistics suggested instead that the appropriate localization of lesions was by convolutions. From these two analyses- that the deficient function in Lebourgne was that of "articulate language", and that the correspondingl esion was in the foot of the third frontal convolution- camet he now famousc onclusiont hat the foot of the third frontal convolution was responsible for spoken language. The 1861 paper by Broca is the first truly scientific paper on language- brain relationships.I t differsf rom previousw ork in a number of ways.F irst, it relieso n a detailedc aseh istory and excellentg rossa natomicalf indingsa t autopsy. Second, it containst he insight that convolutionso f the brain are relatively constantg rossn euroanatomicalf eatures,a nd that they might be related to particular psychologicalf unctions - an idea which has proven worth investigating ever since, and which is still the basis for much neurolinguistica nalysis.T hird, although, as we shall see,t here were many objectionst o and reinterpretationso f Broca'sp aper, the centralc onclusion - that the expressivea pparatusf or speechi s relatedt o a small areao f cortex just in front of the pre-centralg yrus,i n the pars triangularisa nd opercularis of the third frontal convolution- is, if not completelya ccurate,a very good first approximation to what we still believet o be true. Between 1861a nd 1865,B roca published severalm ore clinical caseso f aphasia (or "aphemia" as he called the syndrome), and the "language faculty" becamea widespreado bject of study, as the prime example of the localization of a psychologicalf unction in the nervous system. In 1865, Broca publisheda secondi mportant paper on languaged isorders,t he first to call the attention of the neurologicalc ommunity to the fact that aphasia followed lesionso f the left hemispherea nd not the right. We may note in passing that there is some question regarding who first suggested a "dominant" role of the left hemispheref or language.A n earlier paper by Dax, cited by Broca, had been presentedt o a medicalm eeting in Montpel- lier, but had attractedn o attention. Broca (1t365)p ointed out that eight consecutivec aseso f aphasiah e had observed had had left-hemispherel esions,s omethingw hich he concluded could not have occurredb y chance.H e pointed out that the conclusiont hat the left hemispherei s responsiblef or languagec ontradictedt he very general biological law that symmetrical organs (in this case, the two cerebral hemispheres)h ave identical functions. Broca believedt hat, although there were small differencesi n the patternso f convolutionsf rom sidet o sideo f the brain, these differencesw ere insignificant.T he discovery that there are important lateral asymmetriesi n the human brain had to wait for over a hundred years (see Chapter 18). Rather, the answer lay in embryology:

46 The discoverieso f Paul Broca observationsb y Gratiolet and Bertillon had shown that the formation of sulci occurs first in the left hemisphere in fetal development, and this precocity of the left hemispherep rovided the basisf or its "dominant" role in speech.T he embryologicalf actsa lso accountedf or the determinationo f handedness;t he fact that the majority of people are right-handedw ould be another result of the earlier maturation of the left hemisphere. Broca then added severalo bservationsa nd qualificationst o thesec laims. First, he suggestedth at in certain individualst he right hemisphered evelops before the left, making them left-handed.I t had been known that language wasn ot alwaysd isturbedi f diseasein childhoodo r congenitalm alformations of the nervous system affected the left hemisphere in early life. Broca pointed out that these patients were often left-handed,i mplying that the right hemisphereh ad taken over control both of handednessa nd language. From these observationsa nd inferences,B roca suggestedt hat recovery from aphasiam ight be possiblei f the right hemispherec ould take over the functionsu sually accomplishedb y the left. He concludedt hat the failure of most patientsw ith aphasiat o recoverw as due to inadequater ehabilitative efforts: he thought that adequater ehabilitationw ould have to consisto f as much exposuret o languagea s a child learning a first languageh as with his mother, somethingt hat is hardly ever provided. Finally, he pointed out that the ability of aphasicp atientst o understandl anguagei ndicatedt hat the right hemisphere dld function in the broader psychology of language, which involvest he establishmento f relationshipsb etweene xpressionsa nd mean- ings; the dominanceo f the left hemispherew as for speecha lone. As will become apparent, almost all these conclusions- that the left hemisphere is dominant for expressivel anguage, that this is linked to handednesst,h at recovery from aphasiam ay involve the right hemisphere, that there are developmentale mbryologicald ifferencesb etweent he hemi- spheres, and that the right hemisphere has the capacity for receptive language- are still very much acceptedt oday, with somer efinementsa nd on the basiso f more evidence. How can we evaluateB roca'sc ontribution to the studyo f language-brain relationships?I t is reasonablet o regard him ast he founder of the field. His carefula ttention to anatomicald etail, his willingnesst o advanceh ypotheses on the basis of limited data, the framing of testableh ypotheses,a nd the actual content of the hypothesesh e put forward opened up the field to researchersI.n deed, we are still trying to solvem any of the problemsh e left. For some fifty years after Broca, until World War I, the study of language disorders was a central part of clinical neurology, and virtually every important academicn eurologisti n Europe publishedp apers on the ropic. The descriptiono f the grossn euroanatomyo f the languagea reas,a nd the 47 Il Clinical aphasiology and neurolinguistics clinical classificationo f aphasiasi n use today, were the results of the concentrateda ctivity which followed Broca. Broca himself seemst o have lost interest in the study of aphasiaa fter 1870.B y the time Wernicke publishedt he seminala rticle which led to the productive "connectionist" schoolo f aphasiologyin 1874,B roca had bowed out of the field. He did travel to England in 1866t o discussh is work at a conference,w hich was also attended by Hughlings Jackson; the two men disagreed,a nd Broca is said to have carried the day. He devotedh imself to anthropology, which was probably his major interest.I ndeed, his work on aphasiaw as first discusseda t the Anthropological Society which he had founded, and was a result of his interest in the relationshipb etween brain size and the intellectualc apacitieso f different speciesa nd human races( a controversialt opic, then as now). Like much important scientificw ork, Broca'sh as had a mixed reception. It sparked a tremendous interest in the phenomenon of aphasia and its anatomical basis, as we have noted, but it also drew great criticism and required modifications. First, the connectionistsd iscoveredo ther aphasic syndromes related to lesions elsewherei n the brain. Investigatorst hen discoveredt hat many aphasicp atientsw ho appearedt o be similar to those described by Broca also had various sorts of problems in understanding speech and reading, which called Broca's analyseso f his own casesi nto question. Finally, Pierre Marie and his student,F ranqoisM outier, criticized Broca's neuroanatomicalc onclusions.a nd debated both the clinical inter- pretation and the neuroanatomicalb asis of what, by then, had become known as "Broca's aphasia". We now can see that these debatesa nd criticisms are testimonialst o the high quality and importance of Broca's work, which provided neurolinguisticsw ith many of its basicc oncepts,a nd also with many problems to solve and questionst o answer.

S U G G t s S T I O N S F - O RI . - UR T H E R R L , A D I N G

H6caen. H. and Dubois. J. (1969). Le Naissanced e la Neurcpsychologied u Lungage: 1825- 1865.F lammarion. Parrs. Marshall, J. (19t32)M. odels of the mind in healtha nd diseaseI.n A. Ellis (ed.). Nornmlity and Pathology in Cognitive Function.s.A cademic Press, London. Signoret, J.-L., Castaigne,P ., Lhermitte, F., Abelanet, R., and Lavorel, P. (1984). Redis- covery of Lebourgne's brain: anatomical description with CT scan. Brain and Language 22. 303-19. Young, R.M. (1970). Mind, Brain, and Adaptation in the Nineteenth Century. Clarendon Press.O xford.

48 4

Classicalc onnectionistm odels

The work of Paul Broca establishedth e studyo f aphasiaa sa n important part of clinicaln eurology and nineteenth-centuryn eurosciencef.' he localization of languagec apacitiesin parts of the brain, and the surprisingf act of cerebral dominancef or language,p aved the way for a "scientificp hrenology", the studyo f the relation betweenc onvolutionsa nd other areaso f the brain and "higher functions". From 1861 on, the neurological literature was filled with caser eportso f aphasicp atients,o ften followed by autopsies,a nd, more generally,w ith reports of patientsw ith a variety of psychological,i ntellec- tual, and complex perceptual problems accompaniedb y autopsieso f the brain. The most illustriousn eurologistso f the day publishedp aperso n the subjecto f aphasia. Among other things. it was a major point of interest to confirm or disconfirmB roca's claim that the faculty of articulatel anguagew as located in the posterior portion of the left third frontal convolution. For about a decade,c ontroversy raged about the correctnesso f this claim, as caseso f aphasiaw ere discoveredw hich had lesionse lsewherei n the left hemisphere, andc asesc ame to light of patientsw hosea utopsiedb rainss howedl esionsi n Broca'sa rea, but who had not had disorderso f languagei n life. As Broca pointed out, the latter casesm ight be explained by the right hemisphere taking over speech (though the conditions under which this was possible weren ot completelyk nown), but the former indicatedt hat Broca'sa nalysis couldn ot be the whole story. No unified theory relating all the observations on the aphasiasw as available,h owever,a nd the field became" data rich and theoryp oor", characterizedb y many interestingo bservationsth at could not be understoodw ithin any singlef ramework. In 1874,C arl Wernicke, then a twenty-six-year-oldp hysiciant raining in neuropsychiatry,p ublished a paper which served to create a theoretical frameworkw ithin which thesed isparateo bservationsc ould be approached. He provided a classificationo f aphasics yndromes,a nd a generalm odel of how languagei s representedi n the brain from which new syndromesc ould be predicted. His paper constitutest he third great discoveryo f nineteenth- century aphasiologists:t he discoveryt hat there were severals ub-typeso f

49 ll Clinical aphasiology and neurolinguistics aphasics yndromes, each of which resulted from lesions in different areaso f the brain. One implication of this discoveryi s that languager epresentation and processingb y the brain is such that different areasa ccomplish different tasks. Normal languagea bilitiesr equire the integration of different areas. Wernicke's paper createdt he most productives choolo f study in this field in the nineteenthc entury, and one whosec linical insightsa re still in use. Wernicke's paper was entitled "The symptom complex of aphasia: a psychologicals tudy on a neurologicalb asis". In it. Wernicke describeda seconda phasics yndromea nd predictedt he existenceo f a third. On the basis of these cases,W ernicke set forth a model of languager epresentationa nd processingin the brain, consistentw ith the associationispt sychologya nd the neurophysiologicalt heory of reflexeso f his day. Wernicke describedn ine caseso flanguaged isordersd ue to acquiredd iseaseo fthe brain, ofwhich the first two were the basisf or his theory. Theset wo casesw ere instanceso f an aphasics yndrome very different from what Broca had described.I n both cases,t he patients had a marked deficit in understandingw hat was said to them. The secondp atient, in fact, waso riginally thought to be deaf, because she manifestedn o awarenesso f what other peoplew ere sayingt o her; but it soon became apparent that she was not deaf, but simply unable to under- stand language. As in Broca's case, it was important for an examiner to avoid giving himself away through gestureo r facial expressioni f he wanted to test her ability to understandl anguagep er se,s incet his patient was quite capable of understandinga great deal by observingt he gesturesa nd facial expressionso f the people who spoke to her. Wernicke's two patients also had a great deal of difliculty with spoken language, but the form of the expressivel anguage disorder was quite different from that which Broca had described.I n Broca's original caset he patient was renderedv irtually mute, with the exceptiono f a singlem onosyl- lable. Other casesw ith anterior brain lesionsh ad beend escribed,a nd it was generally appreciated by 1874 that the characteristics peech of these patients,t hough not necessarill'asr educeda s that in Broca'sf irst case,w as alwaysh alting and effortful. Patientsw ith anterior lesionsf requently omit- ted many words, and often showeda greatd eal of difficulty in pronunciation of individual sounds. Wernicke's first two patients had quite different abnormalitiesi n speecho utput. In both cases,t he patientss poke fluently and maintained normal intonational patterns, but were unable to make sense.W ernicke describede rrors which were not in the actualp roduction of soundsb ut in the selectiono f sounds.I nsteado f sayinga particularw ord, his patients might say a word which was related either by virtue of rhyme (or some other aspecto f its sound), or by virtue of somes emanticr elationship. At times, the words that were spoken were so different from words in

50 Class i ca l co nnec t io nis t mo del s

MOTOR COBT!X SOMATTCS ENSORYCORTEX

PARIETAL LOBE BROCA'S AR!A

PRIMARYA UOIIORY ANSA occrPrTALL o8! TEMPORAL LO8!

PRO',ANYV ISUAL AREA

Figure4 -1. Diagram of the brain showingW ernicke'sa reaa nd Broca'sa rea.T he solid line in Wernicke's area representst he junction between the temporal and parietal lobes. The lesion in Wernicke's case occupied the temporal lobe portion of Wernicke's area. (Source: Geschrvind 1979: 11 l)

German that the examinersc alled them "neologisms" - that is, new words which did not existi n the German vocabulary,a nd which were not relatedt o any words in German by normal rules of word formation. The speech of these two patients did not convey information. Wernicke and the other examinersw ere frequently at a loss to understandw hat the patients were trying to say. One of theset wo patientsd ied and her brain camet o autopsy.I t showeda cerebral infarct (a stroke) in the region of the first temporal gyrus on the left, occupying approximately the middle third of the gyrus and extending posteriorly towards the parietal lobe (Figure 4-1). Wernicke pointed out that this area of cortex had two important characteristicsF. irst, it was an area directly juxtaposed to the cortical area which receives the final connectionso f the auditory system,t he post-thalamica uditory radiations. Second,i t was an area which itself was neither a primary sensoryn or a primary motor area. It was one of a number of areasc alled "association" areas,t hought to be involved in more complexe laborationa nd modification of sensorya nd motor information. Wernicke argued that it was reasonablet o considert hat the association area immediately juxtaposed to the primary auditory cortex would be

5 1 ll Clinical aphasiology and neurolinguistics

language' This was in keeping with responsible for understanding spoken around each primary sensory cortex the notion that the association cortex sensory signals which were sent to that was responsible for analysis of the therefore consideredt his area in the first area of primury ,"n,ory cortex' He lesion would cause a disturbancei n temporal gyrus to be one where a and he concluded that the receptive understanding spoken language' his first two patients was due to the lesion' i;;;"g" oeR"ciot f - function of this area the first Wernicke suggested that the normal paper became known as "Wernicke's temporal gyrus (whlch after this the auditory form of words; and he area") - was to be a memory storeioi of its close proxirnity to the central reasoned that it playeJ tni' rott because wernicke suggestedt hat this region termination of the auditory pathway. "t"nit'" for language't he aread escribedb y should be considereda second was hypothesizedt o a Broca being the first. Wernicke's area .accomplish - language;t o contain a particular particularf unction understandings poken - touna pattern of words;.andt o occupy type of linguisticr epresentation ttt" - the first temporal gyrus. In the a specifics ite in the cerebrarh emisphere connectionistliterature,thistriadmoreorlessdelinesa..center,'.Thereare featuresa re absenti n a postulated casesi n which one or another of these notion of a center involves the triple center, but. for the most part' the psycholinguisticfu nction' and a linguis- characterizationo f u b'uin i"gion' a tic rePresentation. W e r n i c k e t h e n t u r n e d t o t h e i n t e r e s t i n g q u e s t i o n o f t h e o r i g i n o f t h e ofthe brain deficitsi n thesep atienti' A closei nspection expressivela nguage a g'otu'' and Wernicke dismissedth eidea that did not show a t",lon oi ut"u' responsiblef or the expressivel anguage second lesion in Broca,s area was that the expressivel anguaged eficit defic;t. Wernicke tnerefore concludeci the receptivel anguaged eficit' and was due to the same lesion that caused that it arose in the following way' two inputs' One is an input from Expressivef u nguug",t t" itgutO' requires from the m-emorys tore for exprJssed'T he secondi s an input a thought to be of words' Wernicke envisageda flow the auditory form of words' In other representations of words and the information between the auditory that went into the articulation of these representationo f motot sequences there was an excitationo f He suggestectlh at, in the act of speaking' words. neural area' which were forwarded in a the memory tracesi n Wernicke's movementsi n the anteriors peech codet o the memory tracesf or articulatory the joint influenceo f "thought" and area. The unt"rto.''p"tch area' under articulatorym emoriest o *"*#"' for words' activatedt hese the auditory of incorporatedt his idea into the first innervate the oral musculature.H e

52 Class ical connectionistm o dels

f

Figure 4-2. Wernicke's first diagram. Wernicke's area and Broca's area are marked as c and b respectively in the temporal and frontal lobes. Input, output, and connecting pathways are indicatedi n schematicf orm. (Source: Moutier 1908: 36) many diagramst hat characterizet his approacht o neurolinguisticss, howni n Figure 4-2. Just as Broca's paper produced the important hypothesist hat linguistic and psycholinguisticf unctions were localized in cerebral gyri, Wernicke's paper introduced the notion of information flow into our concepts of the representationa nd processingo f languageb y the brain. In addition to the notion that normal languagei nvolved the co-operationo f two brain areas, with information flowing from the posteriort o the anterior area,W ernicke's model alsoi nvolved severalo ther features.H e insistedt hat the components of the model and their interaction be justified not only by the facts of aphasia,b ut also by the facts of normal physiology and psychology.H e believedt hat both of theser equirementsw ere met by his theory. In the first case, he pointed to the work of his teacher Meynert, which establishedt hat sensory-to-motorf low of excitation was involved in reflex action, and he argued that languagec ould be seena s an extremelyc omplex modulatedr eflex. If it were seeni n this way, then the notion of information flow from a sensory to a motor area was consistentw ith ideas of the control and origin of most motor movements, as understood in the physiologyo f Wernicke'sd ay. As far as consistencyw ith normal psychologyw as concerned,W ernicke suggestedth at the usual way a child learns languagew as by imitating the languaget hat he heard in the community, and that the first vocalized utterances required a transmission of linguistic information from the auditory receptivea reas,t hrough their associationc ortex, to the structures in the anterior portion of the brain which were involved in controlling the

53 ll Clinical aphasiology qnd neurolinguktics vocal tract. Becauseo f this ontogeneticf actor, Wernicke thought that the many functions resulted from cr auditory-to-motor processo f information flow was a reasonablef eature of thought that the major psycholin any model of normal speaking. speech,s peaking,r eading,a ndwr Two other aspectso f Wernicke's paper are important. The first is his constitute psychologicale ntities prediction about other aphasics yndromes.H e realizedt hat if one type of (although, as we have seen,h e aphasia could be caused by a lesion in Broca's area, leading to a participatei n a singlef unction).$ predominantlym otor syndrome,a nd if a seconda phasics yndromec ould be we have noted that he propos causedb y a lesion in the first temporal gyrus leading to both a receptive psychological function were loc deficita nd an expressived isorder,h is model predictedt hat there would be a examplesa re the Lrestc luest o wl third form of aphasiaw hich arose from a lesion in the pathway between psychologicalf unction. His appr Wernicke's and Broca's areas.W ernicke suggestedth at this pathway lay in because complex functions wt the cortex, and that it was reasonablet o think of the gray matter around the components. Sylvian fissure as constituting a single gyrus related to language,w ith an Wernicke's paper was immedir auditory, sensoryp ole in the temporal portion and a speech,m otor pole in was a young man, without acac the frontal portion. contribution was immediately a1 Wernicke suggestedth at the aphasiat hat would be producedb y a lesiono f dominant way of approachingth e the intervening portions of this gray matter would be characterizedb y an language. This approach is well expressived isorders imilar to that seenw ith posteriorl esions( becauseo f the published in German in 1884a nd interruption of the flow of information from auditory to motor areas),b ut in 1885,w hich setf orth a proposal that the abilities of such patients to understand spoken languagew ould syndromes based upon a connec' remain intact (becauset he associationa rea in which auditory represen- Lichtheim's paper still forms the tations were stored was itself intact). He suggestedt hat, in general,t here fication of the aphasiasin North A was a differenceb etween the aphasiasc ausedb y lesionso f centers,a nd the a major textbook of neurology,e s aphasiasc ausedb y lesionso f connectingp athways. adding three additional syndrom The other point of importancei n Wernicke'sp aper is his effort to restrict they demonstrate.in an extensive the nature and number of centers.W ernicke realizedt hat unlesso ne placed ant classificationso f aphasias incr some restriction on what could be a center and on the number of centers, exclusively in nomenclature,a n( every new form of aphasiac ould be describedb y the postulationo f a new dromes or in the relationshipo f s center, the role of which was the normal performance of exactly the therefore review Lichtheirn'sl 8l languagec apacityw hich wasd isturbedi n a particularp atient. Suchm ultipli- aphasias. cationo f centersa nd connectingp athwaysc ould not Ieadt o a testablet heory Lichtheim produced the diagra of the representationa nd processingo f languagei n the brain. He therefore Wernicke's views essentiallyu nch placed the restrictions we have discusseda bove on the centers that he involved in language- Broca's postulated: the model must be consistent with what is known about thought that the first wasi nvolved psychologya nd physiology.H e alsom ade one more restrictionw ith respect contained the articulatoryr epres( to the centers:t hat they be "simple". the second,h e agreedw ith Werni Wernicke was opposed to the localization of complex and intricate traceso f the auditory form of wor psychologicaflu nctionsi n specifica reaso f the brain which had characterized perception of speech.H e follow the phrenologicala pproacht o cerebrall ocalization.I n its place,h e adopted between Wernicke's areaa nd Br a much more limited notion of what could be localized,a nd thought that there was a "concept area", label

54 C lass icsl co nnec t i o nist mo del s many functions resulted from connecting various brain components. He thought that the major psycholinguisticf unctions- understandings poken speech,s peaking,r eading,a nd writing - could legitimatelyb e consideredt o constitutep sychologicale ntities which could be representedi n a center (although, as we have seen, he believed that two or more centers could participatei n a singlef unction). With respectt o the posteriorl anguagea rea, we have noted that he proposed that a linguistic representation and psychologicalf unction were located in the first temporal gyrus. These examplesa re the best clues to what he meant by the notion of a "simple" psychologicalf unction. His approach became known as "connectionist", because complex functions were built up by connecting "simple" components. Wernicke's paper was immediately successful.D espite the fact that he was a young man, without academic appointment or fame, Wernicke's contribution was immediately appreciated. By 1885, it had become the dominantw ay of approachingt he problem of classifyinga phasicd isorderso f language.T his approach is well exemplified by a paper by Lichtheim, publishedi n German in 1884a nd in English in the influential journal Brain in l8{t5,w hich setf orth a proposalf or a completee numerationo f all aphasic syndromesb ased upon a connectionistm odel of languagea nd the brain. Lichtheim's paper still forms the basisf or the most popular clinical classi- ficationo f the aphasiasin North America. Bensona nd Geschwind( 1971),i n a major textbook of neurology, essentiallya dopt Lichtheim'sc lassification, adding three additional syndromest o the seven he proposed. Moreover, thgy demonstrate,i n an extensiver eview of the literature, that the import- ant classificationso f aphasias ince Lichtheim's work differ from his almost exclusivelyi n nomenclature, and not in substantived escriptionso f syn- dromeso r in the relationshipo f syndromest o areaso f the brain. We shall therefore review Lichtheirn's ltlt35p aper, focussingo n his taxonomy of aphasias. Lichtheim produced the diagram representedi n Figure 4-3. He adopted Wernicke'sv iews essentiallyu nchangedw ith respectt o the two major areas involved in language- Broca's area (M) and Wernicke's area (A). He thoughtt hat the first was involved in speechp roduction, and believedt hat it containedt he articulatory representationsn ecessaryfo r utterances.A s for thes econd,h e agreedw ith Wernicke'sn otion that it containedt he memory traceso f the auditory form of words, and that its function was primarily the perceptiono f speech.H e followed Wernicke in postulating a connection betweenW ernicke's area and Broca's area. In addition, he suggestedt hat therew as a "concept area", labeledB in the diagram,w hich he thought was

55 Double- Doubl click here II Clinicat e- aphasiology and to edit neurolinguistics click text. here 3 to edit text. c)

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Figure4 _4 Lichrheim. Figure4 _3L. ichrheim,s ( diagrar (source: diagramF' ore xplanation, sou r ce; rrr",i., liiisiiicond Mourier, nnr,f jit seer exr.

pllhyuy from in rhe peripheryt c ..:ti;,Tll theb rain.w herhetrh is whicht he ffi"'::l"r shoutdb e consideread patientO omn ot unA, vermy uch difficuttieso f the Werni.t.., rikreh e ,"i1,,r reared for.the ,pi i:"ti1ir.:,,:.liJ:::'fiIj;ilil1;;' auditoryf orm of words ;; ;' uc.rransmttted s ,#";:XT,li""3i::r-1l fi ileoictre,od* i r,im, oddeerp end to the motorc er lesion between M and the oral l,-*' X,# ffi :*H l"'::::,,1 disturbanceo f articulation. of A willcause[ : ;H'h#' i isd isturbed. model werni"t i:,.i"lT' A disordlr .I-ichtheim,s becamec addeda consideration disordero f the conr "', "pr,"rir;il:il:""t"age of thef unc we seeL ichtheim,s predi*e d .;:T:ti extended ia r; *;;;i.Tj:#ilJ# .?Tory of alreadmv adetr, r" ff: :ilf m the visualf orm of-J up atientot repear supportedth . .*irr.nce, ffiit"r|'ll' "utli,t'.i.u.t, wourbde t.hee;l dence In motors equences addition to these classical involvedin v forms of li operate .1_ll^|""*""er, in tt rum. lnputsf rom the concr " J:ffi ffJ:+H,'* aPhasiai::',?i'ffi, *";1":;'; uo.uqu t" riiithep a t:llhu "i *""n g u"a ll':i*t*l'':::,i duet o a disruptioonf iol ;;,#;fJ A,;ffi'."*;'v was an additional ;::1,"'* necessariyn put representation of the oral motr language r.*::dil*trii:'Fil'r"ffilTn:i:xu;determine jreg ue.1t co-occurrence ffri:!',*!tr.t:*iffheh earsU. ntike\i r.;;;l;;ffins"t them eaninogf ol disorde Transcortical to the _linkb etween moroar phasiaa".. i* oughtto b ei nracr. Broca,sa rea, the r"tr#'i^,fllll'li:" As Wernicke had sa mer ypoero ,,o:::1i.nr .o"u:, done, Licl 1 uiffi: T:i,X i l ii;,lilll,"llli for rher unctionin6 ;llj1:li""s exampte ,il;l"?.Tii'J3u; ,i,J"1il",H:tlil:fi I ish isa natysi r'rorl. ouocortrcal :,lirj.r"rt". "Tsen.s*o"ry'a bpheascia,a use,r,.'iu,;l'pu,r,,supov-ntaneous interruiting the speecha nd .epeiiti 56 nelm's model.i t wouldb epossiblt Cl ass i c al co nnec tio nist mo dels

Figure4 -4.L ichtheim'ss econdd iagram.F or explanations, eet ext. (SourceM: outier 19084: 3) pathwayf rom the periphery to A, will lead to "pure word deafness", in which the patient does not understands poken speech,b ut has none of the difficultieso f the Wernicke's aphasici n speakinga loud, sincet he memories for the auditory form of words stored in Wernicke's area are intact and can be transmittedt o the motor centers. Subcorticalm otor aphasia,d ue to a lesion between M and the oral musculature, produces a dysarthria - a disturbanceo f articulation. Lichtheim's model became considerably more complicated when he addeda considerationo f the functionso f writing and reading.I n Figure 4-4, we see Lichtheim's extended diagram incorporating the center O for the memory of the visual form of words. Lichtheim also argued that clinical evidences upportedt he existenceo f a separatea reaf or the representationo f the motor sequencesin volved in writing. This center, E on the diagram, did not, however,o peratei n the samew ay ast he motor centerf or speech.J oint 'inputs from the conceptc enter B, and the visuals toragec enterO , were not adequatet o initiate the proper functioning of the center E. Rather, there wasa n additionaln ecessaryin put from the centerM , the storehousef or the representationo f the oral motor sequenceso f individual words. The frequentc o-occurrenceo f disorders of writing with Broca's aphasiat estified to the link betweenB roca's area, M, and the writing center E. As Wernicke had done, Lichtheim attempted to provide principled explanations for the functioning of the components of his model. An illustrative example is his analysis of the so-called "paraphasic" nature of spontaneouss peech and repetition in Wernicke's aphasra.U nder Licht- heim'sm odel, it would be possible for speecht o result from the triggering of

57 Il Clinical aph asiolog y and neurolingttist ics oral motor commandsi n Broca's area,M , by conceptsi n the conceptc enter between performancesi n a given B. This single pathway from B to M clearly was not the only pathway types of aphasia. involved in triggering motor speech,a s the evidenceo f Wernicke's aphasia Lichtheim did not have the and conduction aphasias howed. Basing his analysiso n Wernicke's, Lich- remained a logical exercisei n l theim therefore suggestedt hat in spoken languageo ne could discern two provide a principle which wou different pathologicals yndromes,a nd that eachs yndromew ast he resulto f a resulted from lesionsi n Wernicl different neuropsychologicalm echanism:t he disturbanceo f Broca's area aphasiaa nd to the form of agrapi itself, M, or the pathway from the concept center, B, to Broca's area, M, cases.T his principle wast hat, wl would lead to slow, halting, effortful speech; whereas disturbance of from two or more other centers, Wernicke's area. A, which was only secondarilyi nvolved in speech.o r the after loss of any one input would pathway from Wernicke's area, A, to Broca's area, M, would result in the followed losso f input from anyo l varieties of fluent, paraphasic, neologistic jargon seen with posterior affected. Though stated in verl lesions. applied to the analysiso f the dis Lichtheim realizedt hat this descriptiono f different syndromesa s a result given that a model of centersa nd of different lesionsc ould be considereda n ad hoc aspecto f the theory, and in particulard omains. he therefore tried to show that the same analysisw as also true of written Lichtheim's paper and his mod language.G iven that written languaged ependedu pon the proper fr,rnction- its greatc linicala nd theoreticailr ing of the center E after its receptiono f some form of relevanti nformation 6, we shall review severalc ritic from center M, there still remained the question of whether the auditory languagea nd ncuralo rganization form of words was involved in writing. Lichtheim suggestedth at the caseso f we shall simply considert hreep r conduction aphasiam ight serve to settle the issue. If conduction aphasics The first of thesep roblemsi st h with a lesionb etweenA and M were totally unablet o write and manifesteda specificdh ism odel.F or instance. syndrome similar to that seen in the spoken languageo f Broca's aphasics, centers in Figures 4-3 and 4-4, it with word omissions, hesitancy,a nd difficulty in the actual depiction of informationm ay travclf rom cenl individual graphemicc haracters,o ne would be justifiedi n assumingt hat the and at worst self-contradictory sole pathway from the concept center B to the writing center E was involving A, B, arrdM , for insta B--+ A-+ M--+ E. If the patientsd evelopedp araphasicw riting (sometimes move in the direction BA. to acco called "paragraphia"), then the pathwaysf or properly activating E would speech.H owever, accordingt o o be in duplicate: there would be a pathway B+ A+ M---+E and a separate the lack of a pathway BA woul, pathway B --+M --+E . A lesiono f the first of theset wo pathwaysw ould lead inability of Broca'sa phasicsto wr to paragraphia,i n exactly the samew ay that a lesioni n the tract A ---+M led centersa nd pathwaysi ss malli n th to paraphasiai n the posterior aphasias.F inally, if conductiona phasicsh ad considerable number of possibi no difficulty whatsoeveri n writing, this would suggest hat the only pathway Lichtheim's paper leaveso ne c involved in writing wasf rom the conceptc enterB to the motor speechc enter decided on particulard irectionsr M and thence to the motor writing center E. Thus, the particular set of The secondp roblem we may cl connections Lichtheim postulated on the basis of the co-occurrenceo f Lichtheim was in fact committe Broca's aphasiaa nd agraphiac ould be tested by other observationsa bout interesting that Wernicke repres patients. This rather complex hypothetical reasoning demonstratest he dotted lines and circlesi n Fig serious effort on the part of Lichtheim (and the other members of the depictions of pathwaysa nd gvri, connectionists chool)t o make the predictionso f their modelse xplicit, and to the right hemisphere).L ichthein characterizei n as principled a way as possiblet he observabled ifferences clear that this differencei s iust

5 8 Class ical con nectio nist mo dels betweenp erformancesi n a given psycholinguisticfu nction in different sub- typeso f aphasia. Lichtheim did not have the data required to settle this issue, which remained a logical exercise in his article. He did, however, attempt to provide a principle which would apply-b oth to the paraphasiasw hich resultedf rom lesionsi n Wernicke's area and to those causingc onduction aphasiaa nd to the form of agraphiaw hich he predictedm ight arisei n these casesT. his principle was that, where the activity of a center required input from two or more other centers,t he disorderedo utput which would result afterl osso f any one input would be qualitativelyd ifferent from that which followedl osso f input from any other, not simply quantitativelym ore or less affected. Though stated in very abstract terms, this principle could be appliedt o the analysiso f the disorderss een after particular brain lesions, givent hat a model of centersa nd their interactionsw as adequatelys pecified in particulard omains. Lichtheim'sp aper and his model had a number of problemsa nd, despite its greatc linical and theoreticali mpact, did not go uncriticized.I n Chapter 6, we shall review several criticisms of the basic assumptionsr egarding languagaen d neuralo rganizationm adeb y Lichtheim'sm odel.A t thisp oint, we shalls implyc onsidert hreep roblemsi nternalt o the model. The first of thesep roblemsi s that it is not cleart hat Lichtheim completely specifiechli s model. For instance,i n interpretingt he linesw hich connectt he centersi n Figures 4-3 and 4-4, it is clearly important to know which way informationm ay travel from center to center. Lichtheim is at best unclear, and at worst self-contradictorya bout this. In the case of the pathways involvingA , B, and M, for instance,L ichtheim requirest hat information movei n the direction BA, to accountf or the activationo f Wernicke'sa reai n speech.H owever, accordingt o one model of writing Lichtheim considers, the lack of a pathway BA would be critically needed to account for the inabilityo f Broca's aphasicst o write normally. Even though the number of centersa nd pathwaysi s smalli n this model, enougha re presentt o allow for a considerablen umber of possibilities of information flow, and reading Lichtheim's paper leaves one quite uncertain as to whether he finally decidedo n particular directionsa nd not on others. The secondp roblem we may considera t this point is the degreet o which Lichtheim was in fact committed to an anatomically based model. It is interestingt hat Wernicke representedh is diagram on a brain (though the dotted lines and circles in Figure 4-2 are not intended to be serious depictionso f pathwaysa nd gyri, and though the model showsl anguagei n ther ight hemisphere).L ichtheim's model is not drawn in this way. It is not cleart hat this difference is just a matter of artistic preference.L ichtheim Il Clinical aphasiology and neurolinguistics certainly makes specifics tatementsr egarding the anatomical location of some of the componentso f the model he presented,s uch as Broca's and Wernicke's areas,b ut, equally clearly, he does not attempt to locate them all. To some extent. such as in the case of the connections between Wernicke's and Broca's area, this is simply a matter of the inadequacyo f existing knowledge: Lichtheim clearly believed that the pathway AM existeds omewherebetweenth eset wo centers.B ut in other areas.i t is not so clear that Lichtheim had any area or pathway in mind, and he may have intended to present a purely psychologicalm odel. The obvious case, of course, is the concept center, which Lichtheim admitted was diffusely located. The problem of directions of information flow is most marked regardingt his center.T he conceptc enterh asa notherp eculiaritya sw ell: it is not subjectt o lesionsc ausinga phasia- that is, there is no aphasics yndrome which Lichtheim recognizeda s a result of a lesion of B. This is the only center or pathway in his entire systemw hich is inviolate in this way. One's strong impression is that Lichtheim really created a mixed model, parts being purely psychological,a nd parts neuroanatomicallyb ased. Finally, we may note that, despite Lichtheim's assertiont hat he was presenting examples of each of the seven types of aphasia his model predicted, many of the detailso f the casesa re vaguea nd his interpretations of the cases he presented are undetermined by the data he had at his disposal.M oreover, as we have seen, some critical observationsw ere not available to Lichtheim, and he could not prove that some of his detailed predictionsa re borne out by data from aphasia. Despite these difficulties,t he model has definite strengths.T hese can be seenb y simply inspectingt he diagramst hat came after his, seeni n the next few figures. In comparison to Lichtheim's, these models are completely divorced from any neuroanatomicalb asis,a nd make useo f connectionsa nd centersw hich have little or no justification,e ither from pathologicald ata or from the normative psychologyo f language.H enry Head (1926) struck a responsiven ote when he labeled the theoretical positions which charac- terized much of this later work "chaos". Not all the work which followed in the connectionists choolw as as undisciplineda s that representedi n Figure 4-5. In the next chapterw e shallc onsidere xtensionso f the basicc onnection- ist model which have conformed to the principles laid down by Wernicke regarding how these models must be constrained,a nd which have led to Figure 4-5. Diagramsof the functioningof and Moeli, developcd in psychologicalf unctions the late nine important insights\ into aspectso f language and commcnts. seet ext. related to language. (Source:M outie r 1908:4 1. 53). The papers of Wernicke and Lichtheim created a framework for the classificationa nd understandingo f aphasias,a nd, simultaneously,a model of the way languagew as representedi n the brain. The model was not very

60 C lass i cs l co nnec tio nist mo del s

Figure4 -5.D iagramspTt he functioningo f the languagea reasa ccordingt o Kussmaul,G rashey, and Moeli, developcd in the late nineteenth century. Initials represent "centers". For commentss. eet ex t. (SourceM: outier I 908: 4l , 53).

6l lI Clinical aphasiology and neurolinguistics detailed with respect to the characterization of language structures or the programs for speech seem m( psychologicalp rocessesw hich make up the various acts of languageu se: tions between centersa re differ speaking, understandings peech, etc. In another sense,h owever, it was have permanent linguistic retr fairly complete. It included considerationo f all the major tasks to which involved in particularf unction languagei s put, and it at leastc laimedt o provide a completee numerationo f tion from one centert o anothe possible aphasic syndromes. There is no doubt that it helped to.guide centers during the accomplishr research,b oth by providing a basisu pon which some workers could build, Connectionistt heoriesh ave and also by providing a theory which others found worth attacking. To ment of theorieso f languager r concludet his chapter, we shall attempt to summarizet he basicf eatureso f they are of tremendousc linical the classicacl onnectionistm odels. ability in eacho f the major psyr Connectionistm odelsa re one type of a group which we may call "faculty" spoken language,r eading,w rit models. Faculty models are those in which the principal languagef unctions able hypothesesa st o the locatir representedi n the brain are entire task-orientedp rocessesI.n Lichtheim's move towards a hypothesisa and Wernicke's models, we see components which are responsible for Especiallyi n the erao f clinicalr speech production, speech understanding, reading, and writing. In the diagnosisw as not available,t he classicc onnectionistm odels, the facultiesw hich are postulateda re almost Second,t he notion ofcenters exclusivelyt he major "on-line" taskso f the psychologyo f language:t asks of organizationo f the language which occur quickly in real time, and in which a speakero r listenerp roduces to the presentd ay. A majorc o or recognizess equenceso f acoustico r graphic elements under time con- the "localizationist" vrew,e xet straints.T hese are the usual "tasks" to which languagei s put. others who were "holists" and In the connectionist models. each of the psycholinguisticf aculties - represent languagei n centers reading,w riting, speaking,a nd hearing- wns considereda s an individual languagep erformancesT. his cr entity. Each was connectedt o the others, and the connectionistm odels do later chapters some of the w allow somep rovisionf or interactionb etweent hesec omponents.A s we have discoveriesi n the field. noted several times, the best examples of this interaction are the trans- Finally, connectionistth eoryr missiono f sound representationsto the componenti nvolved in the produc- of both normal anda bnormall ar tion of articulate speech,a nd the neeessaryp assageo f signalsi nvolved in work. The featureso f language writing through the center involved in articulates peechb efore they reach istic models are the on-linet ask the centerf or the control of thc movementso f writing. However, there is no linguistic units which were par provision with eachc omponent for a truly fine-graineda nalysiso f the tasks languagei n the work of the cor involved in each of the major psycholinguisticfu nctions. only roughly sketched.S imilarl It is in the connectionistm odelst hat the notion clf" center" emergesm ost sion, speaking,a nd other tasks clearly.A centerc onsistso f a singlep sycholinguistifca culty,a ssociatewd ith stressedt he assessmenotf the re one major type oJ storagef or linguistici tems,l ocatedi n a particular areao f on-line tasksa st he essentiaol bs the brain. In th6 caseo f Broca's area, the psycholinguisticfu nction is the tion of aphasicp atients.O n ther production of spoken language,a nd the linguisticr epresentatic)cno nsistso f localizationo f thesef unctionsI the motor programs involved in the production of spoken lnnguage.I n the chaptersw e shalls eeh ow these case of the posterior languagea rea, the faculty is unclerstandings poken detailed analyseso f the nature language,a nd the permanent Iinguisticr epresentatit'lnis the sound pattern processes which are affected i: of words. Note that not all the "representations" are alike - the "sound detailed level of descriptiono f pattern" for words might be a linguistic representation,b ut the motor moving towardsa more detaile< 62 C lass ical con nectionis t mo del s programs for speech seem more "motor" than "linguistic". The connec- tions between centers are different from the centerst hemselves.T hey do not have permanent linguistic representations, and they themselves are not involved in particular functions as a whole. Rather, they transmit informa- tion from one center to another, in order to allow the proper functioning of centersd uring the accomplishmento f particular psycholinguisticta sks. Connectionist theories have played a very significant role in the develop- ment of theorieso f languager epresentationi n the brain. In the first place, they are of tremendousc linicalu tility. The clinician,b y assessinga patient's ability in eacho f the major psycholinguisticta sks- speaking,u nderstanding spokenl anguage,r eading,w riting, and repetition - is able to make reason- ableh ypothesesa st o the locationo f the lesionp roducingt he aphasia,a nd to move towards a hypothesis as to the pathological cause of the lesion. Especiallyin the era of clinicaln eurologyi n which sophisticatedra diological diagnosisw as not available,t heseh ypothesesw ere often the best available. Second,t he notion of centersa nd connectionsb eingt he principal method of organizationo f the languagea reaso f the brain hass timulatedr esearchu p to the presentd ay. A major controversya roseb etweent hose who favored the "localizationist" view, exemplifiedb y the connectionista pproach, and othersw ho were "holists" and believedt hat the brain did not processa nd representl anguage in centers devoted to particular sub-componentso f languagep erformances.T his controversyi s not settled,a nd we shall seei n later chapters some of the ways that this controversy has led to new discoveriesin the field. Finally,c onnectionistt heory defineda levelo f observationa nd description of both normal and abnormall anguagew hich stronglyi nfluenceds ubsequent work. The featureso f languagew hich enter into connectionistn eurolingu- isticm odelsa re the on-line taskso f languageu se,a sw e have indicated.T he linguisticu nits which were part of the descriptionso f aphasica nd normal languagein the work of the connectionists- words, sounds,s yllables- are only roughly sketched.S imilarly, the detailso f the processeso f comprehen- sion,s peaking,a nd other tasksa re not considered.T he early connectionists stressedth e assessmenotf the relativeq uantitativei mpairment of eacho f the on-linet asksa st he epsentiaol bservationsn eededf or diagnosisa nd classifica- tiono f aphasicp atients.O n the neurologicals ide,c onnectionisme mphasized localizationo f these functions in gyri and groups of adjacent gyri. In later chaptersw e shalls eeh ow thesef irst modelsh ave been criticized,h ow more detaileda nalyseso f the nature of the linguistice lementsa nd psychological processesw hich are affected in aphasia have led to an empirically more detailedl evel of descriptiono f languaged isorders,a nd how we are slowly movingt owardsa more detaileda nalysiso f the neural basisf or language. 63 Il Clinical aphasiology and neurolinguistics

S U G G E S T I O N S F O R F U R T H E R R E A D I N G perspectivel n t Arbib,M.,Caplan,D.,andMarshall,J.c.(1982).Neurolinguisticsinhistorical M . A r b i b , D . C a p l a n , a n d J . C . M a r s h a l l ( e d s . ) , N e u r a l M o d e l s o f L a n g u a g e P r o c e s s e s . Academic Press, New York. ln A' B' Benson, D. F. and Geschwind,N . (1971).A phasia and relatedc orticald isturbances Extensionso f connectioni Baker and H. Baker (eds.), Clinical Neurology' Harper and Row, New York' University Head, H. (1926). Aphasia and Kindred Disorders of speech (section 1). Cambridge Press, Cambridge Lichtheim, L. (1885).O n aphasia.B raini ' 433-84' of language.I n D. Caplan' A. R. Morton, J. (1984).B rain-baseda nd non-brain-basedm odels L e c o u r s ' a n d A ' S m i t h ( e d s ' ) , B i o l o g i c a l P e r s p e c | i v e s o n L a n g u a g e . M I T P r e s s , C a m - The work of Wernicke, Lichtheir bridge, Mass. investigatorsd ealt mainlyw ith th Breslau'R eprintedi n Wernicke, C. (1874).T he aphasics ymptomc omplex.K ohn and Weigart, Studiesi nthe Philosophy of "faculty for language".T he ident translation in R. S. Cohen and M. w. warofsky (eds.), Boston Science.v ol.4. Reidel, Boston. faculty, the delineationo f interacl neural loci of thesec omponentsi debated in the neurologicall itere many variations of thesem odels. chapter are quite typicalo f thew o this work, which would be far be1 cannot devote all our text to the la analysisv ery much in keepingw it analysiso f the syndromeo f alexia with malice aforethought.I t serve the agnosiasa nd apraxiasu ndertt which we shall mention briefly; century description, we will be refinemento f viewsr egardingt his 14, we shall reconsidert his syndr< In 1892,J ules Dejerinep ublishr autopsy findings of a patient witl patient was an engineerw ho had r read words, sentenceso, r letters. half-field. He was unablet o nam( musician. able to sight-readm us however, able to write, both sponr copy, but he had a peculiarw ay o print into print asi f eachw erea de read the very things he himself between the writing and the atter material. At autopsy, the brain showedt entire left occipitall obe. in the dir

64 5

Extensibnso f connectionism

The work of Wernicke, Lichtheim, and many other late nineteenth-century investigatorsd ealt mainly with the variousp artso f what may be termed the "faculty for language".T he identificationo f elementaryc omponentso f this faculty, the delineation of interactions of components, and the searchf or the neurall oci of thesec omponentsa nd their connectingp athways,w as much debatedi n the neurologicall iterature of that period. Although there were many variations of these models, those we have discussedin the previous chaptera re quite typical of the work in this tradition. We shalln ot review all thisw ork, which would be far beyond the scopeo f an introductory text (we cannotd evote all our text to the lastc entury), but we will considero ne more analysisv ery much in keepingw ith the connectionista pproach, Dejerine's analysiso f the syndromeo f alexia-without-agraphiaT. he examplei s chosen with malice aforethought. It servesa s a natural bridge to the approachest o the agnosiasa nd apraxiasu ndertakenw ithin the connectionistf ramework, which we shall mention briefly; and, having considered its nineteenth- century description, we will be able to appreciate a twentieth-century refinemento f viewsr egardingt his syndromel ater in this chapter.I n Chapter 14,w e shall reconsidert his syndrome from a psycholinguisticv iewpoint. In 1892,J ulesD ejerine publishedt he caseh istory and neuropathological autopsyf indings of a patient with a striking set of difficulties. Dejerine's patientw as an engineerw ho had suffereda stroke which left him unable to readw ords, sentencps,o r letters. He was unable to see in the right visual half-field.H e was unable to name colors. He had been a talented amateur musician,a ble to sight-read music, and he had lost this ability. He was. however,a ble to write, both spontaneouslya nd to dictation. He was able to copy,b ut he had a peculiarw ay of copying: he copied script into script and print into print asi f eachw ere a design.M ost dramatically,h e wasu nablet o read the very things he himself had written if enough time had elapsed betweent he writing and the attempt to read for him to have forgotten the material. At autopsy.t he brain showed the lesion diagrammedi n Figure 5-1. The entirel eft occipitall obe, in the distribution of the posteriorc erebrala rtery,

65 Ll Clinical aphasiology and neurolinguistics

orthographic forms. If this wert receptiono f visuali nformationa n which a patient could not read. account for the patient's preserl involve accessinga uditory and < entirely in the undamagedp ort preserved. Writing to dictation entirely involving the undamaged This analysisi s an exampleo centers and connectionst o the ci early twentieth centuries,t he besr disconnectiono f motor and senso the language areaso f the left he "agnosias". Alexia-without-agral agnosia- an agnosiaf or the writte conditions in which a subjectc an1 tecc inlirieure rlu eerveau. Plaque lorrne anci|nne de lq osrtie 'Dolt{rlcurc des lobuler liogurl et frrsiloime de l bauisphirc gaucle. appreciatei ts significanceo r mea match the object to one with a si Figure 5-l. Dejerine's diagram of lesioni n his caseo f pure alexia (Source:D ejerine 1892:f ig. 4) indicate its function or matchi t to objects. The agnosiasc anb e seen certain forms of agnosiah aveb ee was infarcted, accounting for the right hemianopsia. ln addition, the perceptual abilities and language posterior part of the corpus callosum,t he splenium, was also infarcted, as agnosiass, eeC hapter1 2.) occasionally occurs in vascular lesions because of the particular areas The apraxias, by way of cont supplied by the left posterior cerebrala rtery. planning, some of which may als Dejerine suggestedt hat the alexia could be explained in the following tions. The apraxiasw ere describe manner. The patient could see items in the left visual field, which were (1900; Liepman and Maas 1907) relayed normally to the right occipital lobe. However, this material could patients who were unablet o perfo not be transferred in a visual form to the left hemisphere, becauset he to verbal commandsw ith the left i pathway foi transmissid of information from the visual associationc ortex the left hand perfectly normallyi r in one hemispheret o that in the other lies in the splenium of the corpus verbal commands.H e suggestetdh callosum,w hich wasd estroyed.T herefore, althought he patient could seei n in the anterior portion of the corpu the left half-field, he was unable to convey visual information to the on the right from the languagea rr languagea reasi n the left hemisphere,a nd he could not establisha relation- confirmed at autopsy,l eadingt o a ship between the visually presented orthographic representations of apraxia. languagea nd the auditory representationso f languagew hich are stored in For a variety of reasons,c onn! the left hemispherea lone. Dejerine arguedt hat readingi nvolvedt he pairing were ignored for some fifty years of a graphemico rthographic representationw ith a phonologicalr epresen- suggestedt hat some of the reasonr tation before the retrieval of semantic information about a word or a developed mainly in Germany,w J sentence. He postulated that there was a center for reading in the left were certainly scientific,a s critic parietal lobe, where the sound values of letters were paired with their developed (see the followins chat

66 Extensionso f connectionism orthographic forms. If this were the case. a disconnectionb etween the receptiono f visuali nformation and this centerw ould producea syndromei n which a patient could not read. Moreover, this explanation would also account for the patient's preserved ability to write. Since writing would involve accessinga uditory and orthographic representationsw hich were entirely in the undamaged portion of the left hemisphere, it would be preserved.W riting to dictation would also be possible through a route entirely involving the undamagedp ortions of the left hemisphere. This analysisi s an example of the natural extension of the theory of centersa nd connectionst o the callosals yndromes.I n the nineteenth and earlyt wentieth centuries,t he best exampleso f sucha nalysesd ealt with the disconnectiono f motor and sensoryf unctionso f the right hemispheref rom the languagea reas of the left hemisphere- the so-called" apraxias" and "agnosias". Alexia-without-agraphia can be seen as a special type of agnosia- an agnosiaf or the written form of words. In general,a gnosiasa re conditionsi n which a subjectc an perceivea stimulusa dequatelyb ut cannot appreciatei ts significanceo r meaning. Confronted with an object, he may matcht he object to one with a similar shapeo r texture, but be unable to indicatei ts function or match it to another member of the samec ategoryo f objects.T he agnosiasc an be seena s high-leveld isorderso f perception,a nd certainf orms of agnosiah ave been interpreted as disconnectionsb etween perceptuala bilities and languagef unctions. (For more discussiono f the agnosiass,e eC hapter 12.) The apraxias, by way of contrast, are high-level disorders of motor planning,s ome of which may also be seen as verbal-planningd isconnec- tions.T he apraxiasw ere describedf irst in a serieso f papersb y Liepmann (1900;L iepman and Maas 1907). Liepmann discoveredt hat there were patientsw ho were unaQlet o perform skilled motor movementsi n response to verbalc ommandsw ith the left hand, even though they were able to use the left hand perfectly normally in taskst hat did not involve responsest o verbalc ommands.H e suggestedth at this syndromew ast he resulto f a lesion in the anteriorp ortion of the corpusc allosum,d isconnectingth e motor strip on the right from the languagea reaso n the left. This prediction was later confirmeda t autopsy, leading to a "disconnection" analysiso f this form of apraxia. For a variety of reasons,c onnectionistt heories became unpopular and werei gnored for some fifty yearsf rom the 1910st o the 1960s.I t has been suggestetdh at some of the reasonsm ay be political - connectionistm odels developedm ainly in Germany, which lost both great wars. Other reasons were certainly scientific, as criticisms of connectionisma nd alternatives developed( see the following chapters). However, though connectionism

67 ll Clinical aphasiology and neurolinguistics was neglected,i t did not die - in fact, it was revived in a major way in the 1960s. In 1965, Geschwindp ublished a paper in Brain entitled "Disconnection syndromes in animals and man". This paper presented a review and reinterpretation of a number of clinical syndromes in humans and experimental work in primates, largely based on an extension of the rc|milbry nineteenth-centuryc onnectionista pproacht o the higher functions.A good deal of the paper is devoted to an analysiso f disorderso f movement and legchrm sensation, but there are in addition important analysesa nd suggestions regardingt he representationo f languagei n the brain - the areai n which the 9yrur connectionista pproach was originally developed. In severalo ther papers Geschwinde xtendedt his generala pproacht o the considerationo f a variety of clinical disorderso f language.T he remainder of this chapter will con- centrate on this reformulation of the nineteenth-centuryc onnectionist r theorieso f languager epresentationi n the brain. ds,o. Eltet I '-"r^ In the 1965 Brain paper, Geschwind first considersa number of syn- I "-H-e dromes in animals which he argues can be viewed as disconnections yn- i dromes.T he first of these,a nd the one which is analyzedi n most detail, is the Kluver-Bucy syndrome. The syndrome can be produced in a variety of species,s uch as the macaque( a specieso f monkey), by bilateral, anterior temporal lobe resections.S everal changesi n behavior occur in this syn- J-7^ drome. The animal becomes tame and allows itself to be handled by humans, a responseq uite unlike its normal reaction to humans when it is cagedo r in the wild. lt manifestsa marked tendencyt o put all sortso f objects into its mouth, both those which are edible and those which are not. It L" develops an abnormality in sexual behavior and sexual preference, Figurc.5-2.D iagram of thc limbicl obe.T l demonstratingi ncreasedm asturbatoryt rctivity,w ith malesm ounting other hemisphere. In this diagrarn.t hc brain i frontal lohcs arL'r otaled so that thelr inn males and females who are not estrous.A ffected animals contravenet he Figurc (B) showst hc undcr-surfacoef tht normal social hierarchiesi n activitiess uch as grooming. A final character- (,9ource: Daly l9fi5: 2t{) istic of these animals,p erhapsr elated to their tameness,i s a lack of fear of objects, such as snakes,w hich thesea nimalsa re usuallya fraid of. (seeF igure5 -2).T hisc ntirec ircui Geschwind suggestedt hat there is an explanation for this pattern of "lobe" or "system'"i n the brain. behavior which is based upon an understandingo f the anatomy of the of endocrines ecretionb y the pit connectionsb etween visual cortex and the limbic lobe. The limbic lobe sustainingm echanisms ucha se consistso f a circuit, beginningw ith neocortexi n the cinguluma nd the white thought to be importanti n the ar matter buried within this gyrus, and continuing by way of the pericallosal be seen as an anatomicali nterfz gyrus into the more primitive cortex of the hippocampusi n the medial more automatic regulatoryc ent temporal lobe. This circle is completed by a white-matter tract from the system( MacLean 1949). hippocampust o the mammillary bodies( the fornix), a secondt ract from the ln the macaque.G eschwinda r; mammillary bodies to anterior and medial thalamic nuclei, and, finally, visual associationc ortex to the through projectionsf rom theset halamicn uclei, back to the cingulateg yrus retinap assesth rought het halami

68 Extensionso f connectionism

i

miitroin rcgffirum

il-; '

-fhc Figure5 -2.D i:rgramo f thc limbic lotrc. uppcr figurc (A) showst hc linrbick rbe ol the right hemispherc.I n this diagram. the brain is sccn Irom its undcr-surface,a nd thc parietal and frontall ohcsa rc rotatcd so that thcir inncr sutlacc crrnb c visitrlca s illustratcdi n the arrou. Figure( B) showst hc unclcr-surfaceo l tlrc trrlrinr ndicatinul imbic structurcs. (Source:D aly I 9t35:2 ti)

(seeF igure5 -2).T his entirec ircuit,d escribedb y Papez( 1937),c onstitutesa "lobe" or "system" in the brain. whosem ajor functionsa re the regulation of endocrines ecretionb y the pituitary, and thc control of vegetativea ncl sustaininmg echanismss ucha s eating,d rinking, and sexualf unction. It is thought o be importanti n the arcaso f emotiona nd motivation,a nd it can be seena s an anatomical interface between advancedn eocortex and the more automaticr egulatoryc enterso f the brain-stema nclt he endocrine system( Macl-ean 1949). In the macaque,G eschwinda rguest hat there are major connectionsf rom visuala ssociationc ortex to the limbic lobe. Visuerli nformation from the retinap assetsh rought he thalermirce lays tation,t he lateralg eniculatet,o the

69 lI Clinical aph asiol o g1ta nd neurol ingu istir:s primary visual koniocortex in the occipital lobes (the sensory receptor disconnections yndromesi n anima cortex relatedt o vision in area l7 of both hemispheres)F. rom here, it passes ing becausei t reflectsa basica nator only a short distancef orward to the so-called" visual associationc ortex", an sensorya ssociationa reasp rojecti r area of neocortex similar to the auditory associationc ortex in the first in the primate. Geschwinda rgues temporal gyrus (which is the area Wernicke consideredc rucialf or auditory primates and other infrahuman s1 comprehension).T he function of visual associationc ortex, areas1 8 and 19, animal-learninge xperimentsa. sso( is apparently the analysiso f prirnitive sensoryd ata arriving in visual cortex stimulus" sucha sf ood or water anr into patternsw hich are of greaterp sychologicailm portancet o the organism. form or an auditory percept. Whar This pattern of connectionsf rom primary sensoryc ortex (in this casev isual) task of forming associationsb etw to associationc ortex is typical of the higher primates.A ccording to Fleisig's instance,i n so-called" preconditio rule, the output from the primary sensory koniocortices is always very presentedw ith a tone and a visual restrictedi n its dispersion.i n all casesg oing no further than the sounding motor task in responset o the visua associationc ortex. The output from this associationc ortex, however, can the performanceo f the motor task passv ery widely in brain. In the macaque,t herea ret hreep rincipalo utputs image was initially paired. Geschr from visual associationc ortex: paucity of direct connectionsb etv areas themselves.w ith the vast n (l) via the spleniurno f the corpusc allosumt o the equivalenat reao n the going opposites ide; in separatet ractst o the limbi (2) via the white-mattetrr actk nowna st hes uperiorlo ngitudinafla sciculutso therefore be paired with a "limbic' the centersin thef rontall obesi nvolvedin eyem ovements; This example of a disconnectior (3) portion via anotherm ajor white-mattetrr act to the inferolateral of the capacitiesi n the macaques ervea temporallo be. regarding the anatomical basiso : It is this third connectionw hich is irnportanti n the understandingo f the nature of a number of disordersc anatomical basis of the Kluver-Bucy syndrome. The output from the points out that the anatomicala inferolateralt emporal lobe is by way of the anterior temporal lobe to medial substantially different from that temporal lobe limbic structures.p articularlyh ippocampus.T he destruction projections from primary corticals of tissue in the Kluver-Bucy syndrome involves the pathway from the ing associationa reas.s till holds;b t inferolateral temporarll obe to the hippocampusa nd other medial temporal areasp roject to a structuren ot foul structuresin volvedi n the limbic system. structure is the inferior parieta Geschwind explains the constellation of functional deficits in these supramarginala nd angularg yrus.I animalso n the basiso f thesea natomicalc onnectionsa sf olkrws. FIes uggests visual association cortex. auditor that the functional deficit can bc seen as a disconnectiono f visual stimuli associationc ortex project to thiss t from their biological" meaning" for the organism.T he monkey is able to these three associationc ortices.T seea nd discriminatev isualo bjects,b ut unablet o appreciatet heir signifi- representing an example of phy cance. It therefore approaches objects that it would ordinarily avoid, cortex. This structure is absenti n demonstratesn o fear of thesc objects, is unable to make the correct Figure 5-3). selectiono f sexualp artners, violatest he social hierarchy, and is unable to Geschwind suggeststh at the fun learn which of the variouss timuli in his environmenta re ediblea nd which for the associationo f non-limbic are not. Those aspectso f visual stimuli which are relevant to the functions from the limbic system"a nd perm servedb y the limbic lobe are unavailableto the monkey, and his behavior between stimuli in the auditory,s o reflectst his deficit. each of them being reinforcedb y Geschwind suggestst hat this deficit can be seen as one of a number of memory disordersf ollowing disru '70 Extensions of connectionism disconnections yndromesi n animals.T his syndromei s particularlyi nterest- ing becausei t reflectsa basica natomicalf eatureo f the primate brain. All the sensorya ssociationa reasp roject in a fairly direct fashiont o the limbic lobe in the primate. Geschwinda rguest hat this is consistentw ith the abilitieso f primates and other infrahuman speciesi n learning associations.I n most animal-learninge xperiments,a ssociationsc an be formed betweena "limbic stimulus" sucha sf ood or water and a "non-limbic stimulus" sucha s a visual form or an auditory percept. What is difficult for infrahuman speciesi s the task of forming associationsb etween two non-limbic percepts.T hus, for instance,i n so-called" preconditioning" experiments,i n which animalsa re presentedw ith a tone and a visual image and are then taught to perform a motor task in responset o the visual image, the monkey doesn ot generalize the performanceo f the motor task to the auditory tone with which the visual imagew as initially paired. Geschwind arguest hat this is the result of the paucity of direct connectionsb etween the visual and auditory association areast hemselves,w ith the vast majority of fibers from these areas each goingi n separatet ractst o the limbic lobe. Each "non-limbic" stimulusm ust thereforeb e paired with a "limbic" stimulusf or associationt o occur. This example of a disconnections yndrome and the analysiso f learning capacitiesin the macaque serve as an introduction to Geschwind'sv iews regardingt he anatomical basis of language capacity, and regarding the natureo f a number of disorderso f languages een in humans. Geschwind points out that the anatomical arrangement of fibers in the human is substantiallyd ifferent from that in the primate. Fleisig's rule, that the projectionsf rom primary cortical sensorya reasa re limited to the surround- ing associationa reas,s till holds; but the efferent fibersf rom the association areasp roject to a structuren ot found in non-humans peciesT. his important structure is the inferior parietal lobule, consisting of two gyri, the supramarginaal nd angularg yrus.I n the human, the majority of fibersf rom visual associationc ortex, auditory associationc ortex, and somesthetic associatiocno rtex project to this structure,w hich is found at the junction of theset hree associationc ortices.T his structure is histologicallya dvanced, representinga n example of phylogenetically late, complex association cortex.T his structure is absent in all speciess tudied other than man (see Figure5 -3). Geschwinds uggeststh at the function of this structurei s to act as a center for the associaliono f non-limbic stimuli, thus allowing man to be "freed from the limbic system" and permitting him to establishd irect associations betweens timuli in the auditory, somesthetic,a nd visualm odalities,w ithout eacho f them being reinforced by a limbic event. The occurrenceo f major memoryd isordersf ollowing disruption of the limbic systemi n man shows

7l ll Clinical aphasiology and neurolinguistics

extent to the notion of a center literature. A particularp sycholing a particulars eto f linguisticre presr the representationso f sensoryp t Frontalo perculum particular area of the brain, the in There are several differences I centert o be found in the earlierl itt I set of representationsa ssigned ^ ) representation( the soundso f wc iY (the coded sensoryp ropertieso fol \ going on in this area. In fact, it is either of theser epresentationosr. while they themselvesa re stor( Lrmen Insula representationsa re not actuallys tr actually actsm ore like a pathwayi like a center. A second differer Temporal operculum functioning attributed to the infer not one of the usualo n-linep sych parietal lobe Figure -5-3.C onnections of the human inferior ing spoken speech,w riting, and rt (Modified from Carpenter and Sutin 1983:3 1) that of assigningn ames to obje that the limbic systemi s critically involved in human memory' but its role is properties reflectingt he physical not so pervasivea s to preclude the laying down of cross-modaln on-limbic assumet hat activatingt he wordsf < associationsa, s is the casei n infrahuman species. psychologicalp rocessesa s namin Geschwind argues that this anatomical arrangement and its functional function within the "task" of spe importancea re criticali n the developmento f human language.A ccording to region, would thus be a necessarr histheory, it is this arrangement and this functional capacity which allow would seem to function similarly the deveiopment of naming. Geschwinds uggeststh at the most basica ct in' function in speech production ( language is the assignmento f names to objects. He analyzesn aming as suppliest he soundp atterno f wor - - of the psychological associationo f a sound the name and other A third, and very important, "pohnyisiritcinagl p roperties of the named object. He suggestst,h erefore, that the model from those of the nineteer area of anatomical basis of naming is to be found in the existence of an ment to an anatomicalb asisf or th convergence of fibers from the associationa reasf or the separatem odalities postulates. There are no disem in the inferior parietal lobule. The absenceo f this anatomicala rrangement "concept centers" in his work. in non-humani precludest he developmento f naming, and hence of other explicit about which anatomicapl i aspectso f language. can see from his analysiso f the s if *" .o*pure this theory to those that we discussedi n Chapter 4, it is utilizes comparative neuroanato: clear that there are many similarities. we noted in chapter 4 that the neuroanatomicala nalysisin the hr connectionists argued for the existence of centers, each of which was attention to the precise delinea of involved with a particutar languagef unction, contained a particular form nature of the languagea reasw a linguistic representation in long-term storage, and was located in a particu- important asymmetriesi n the sii lar area of the brain. Geschwind's analysiso f naming correspondst o a large sphereso f the brain.

1) Extensions of connectionism extent to the notion of a center that emerged in the nineteenth-century literature. A particular psycholinguisticfu nction. naming, is associatedw ith a particular seto f linguisticr epresentationst,h e soundp attern of words and the representationso f sensory properties of objects, and is located in a particular area of the brain, the inferior parietal lobe. There are several differencesb etween this analysisa nd the notion of centert o be found in the earlier literature. One is that there is more than one set of representationsa ssignedt o the center: in this case, a linguistic representation( the sounds of words) and a non-linguisticr epresentation (the codeds ensoryp ropertieso fobjects) are both involvedi n the processing going on in this area. In fact, it is not clear whether this area itself houses either of theser epresentations,o r is simply involved in their juxtaposition, while they themselves are stored in other areas of the brain. If the representationsa re not actuallys toredi n the inferior parietal lobe, this area actuallya ctsm ore like a pathway in Lichtheim'so r Wernicke'sm odelst han like a center. A second difference lies in the type of psycholinguistic functioninga ttributed to the inferior parietal lobe. First, this functioning is not one of the usual on-line psycholinguisticta skso f speaking,u nderstand- ing spokens peech,w riting, and reading. It is rather an additionalf unction, that of assigning names to objects, or, conversely, assignings emantic propertiesr eflectingt he physicalc haracteristicso f objects to names. If we assumeth at activatingt he words for objectsd uring speechi nvolvest he same psychologicapl rocessesa s naming an object one sees,w e can include this functionw ithin the "task" of speaking.T his process,a nd this anatomical region,w ould thus be a necessaryc omponent in speech.I n this way, they would seem to function similarly to how Wernicke's area was thought to function in speech production (recall that Wernicke's area obligatorily suppliesth e sound pattern of words in speech,o n the classicv iew). A third, and very important, feature which distinguishesG eschwind's modelf rom those of the nineteenth-centuryc onnectionistsi s his commit- mentt o an anatomicalb asisf or the functionalc omponentsa nd processesh e postulates.T here are no disembodied psychologicale lements such as "concept centers" in his work. Geschwind goes to great lengths to be explicita boutw hich anatomicalp athwaysa nd regionsh e hasi n mind. As we cans eef rom his analysiso f the species-specifiacs pectso f naming, he also utilizesc omparative neuroanatomical data to help ascertaint he correct neuroanatomicaal nalysisi n the human. In Chapter 18,w e shalls eet hat this attention to the precise delineation of the neuroanatomicale xtent and natureo f the languagea reas was to lead Geschwind to the discovery of important asymmetriesi n the size of comparable areas in the two hemi- sphereso f the brain.

I J lI Clinicql aphasiology and neurolinguistics

We have not considered Geschwind's analysiso f aphasics ymptoms, only letters, at leastt o a greatere xtent his analysiso f a normal function - naming - and its neuroanatomical basis. patient was able to read numbers In terms of the forms of argument we discussedi n Chapter 2, this analysisi s patientsw ith this syndrome.G esch an "argument from parallel structures". Geschwind (1965) also presents istic of thesep atientst o be unable important analyseso f many aphasic symptoms and syndromes, and of the identical colors. Dejerine's patir agnosiasa nd apraxias.M any of Geschwind'sa nd other modern "connec- literature. have been able to nam tionist" analyses of aphasic disorders are fairly close to those of the presented visually. For instance, nineteenth-centuryc onnectionists,t hough, in all cases,s uch analysesa dd pictures of complex industrial to linguistic and psychologicald etails to the description of a languaged isorder. information passest hrough the s1 We shall not review this work here, partly becausem any of these descrip- languagea reas,i t is hard to seeh c tions will appeari n our discussionsin Part III. We will simply note that, in a becausea ll visual informationi s in major textbook accounto f the aphasiasB, ensona nd Geschwind( 1971)u se in thesep atients. Lichtheim's taxonomy as the basisf or a clinically oriented classificationo f There are three possiblew ayst o aphasia.I n addition to the sevent ypes of aphasiad escribedb y Lichtheim, be the caset hat somev isualr eprese they add three: anomic aphasia, in which the patient has a particularly the left hemispheret hroughm ore marked difficulty in naming visually presentedp ictures and objects; ilola- and some are not. Second,s ome tion of the speecha rea,i n which the patient can repeatb ut neithers peakn or formed into other forms of represe; understand( due to a combinationo f the lesionsw hich produce Lichtheim's type representationsw. hich can cr transcorticals ensorya nd transcorticalm otor aphasia);a nd global aphasia, other types of visual representatio in which all modalities of languageu se are severelya ffected. In all these visual representationsm ay be assc syndromes,m odern connectionismp rovidese xacta natomicala nalysest o a hemisphere.a nd othersn ot. greatere xtent than the first connectionistw ork we discussedin the previous Geschwind (1965) opts for the chapter. In part this is due to a better understandingo f human and non- analysiso f the retaineda bilityt o na human neuroanatomy, as illustrated in Geschwind 196-5i:n part it results this ability becausev isuallyp resen from improvement in neuro-imagingt echniquesw hich allow lesionst o be in other modalitiesi n the right hen detectedi n life (seeC hapter 19). of a piece of fruit, for example,a p One final feature of modern connectionista pproachesd eservesp articular gustatory, olfactory. and other ser comment, for it constitutesa n important additiont o the traditionala nalyses. This associationo f sensoryq ualitie: Much modern work explores the possibility that the brain makes use of the object in Geschwind'st heory, duplicate or multiple mechanismsf or accomplishinga task, some of which qualities in other modalitiesc an b may be more efficient than others. Brain damagem ay revealt he operation rnore anterior portionso f the corpr of someo f the lesse fficientm echanismsw, hich ordinarily are supersededb y Geschwind claims that. to a firr the preferred ones. stimuli which are linguistics ymbolr A good example of an analysiso f this sort in modern connectionismi s left hemisphere when the splenit Geschwind's analysiso f the syndrome of alexia-without-agraphiaa, nd of presumably, do not arouse assoc the agnosias.G eschwind( 1965)n otest hat thesep atientsa re unablet o form hemisphere directly, but require t "visual-auditory associations"o f certain types, as we saw earlier in this tations of words in the left hem chapter, but emphasizest hat they retain their abilitiest o form other such irctivatingt hesea ssociations. associationsF. or example,t he patient describedb y Dejerine sufferedf rom This will accountf or object nan pure word blindnessa nd was unable to read words. He was also unable to Geschwind considerst he ability read letters. In other casesi n the literature, patientsh ave been able to read readins words and letters.b ecause

74 Extensions of connectionism letters, at least to a greater extent than they could read words. Dejerine's patient was able to read numbers and do calculations,a s is true of most patientsw ith this syndrome.G eschwindh asp ointed out that it is character- istic of thesep atientst o be unable to name colors, although they can match identical colors. Dejerine's patient, and most of the patients in the literature, have been able to name pictures and objects when they were presented visually. For instance, Dejerine's patient was able to name pictures of complex industrial tools. On the assumption that all visual information passest hrough the splenium of the corpus callosum to the languagea reas,i t is hard to see how some of thesef unctions are retained. becausea ll visual information is initially presentedt o the right hemisphere in thesep atients. There are three possiblew ayst o accountf or thesep atterns.F irst, it could be the caset hat somev isualr epresentationsa re transmittedf rom the right to the left hemispheret hrough more anterior portions of the corpus callosum and some are not. Second, some visual representationsc ould be trans- formed into other forms of representation.s ucha ss omesthetico r "image"- type representations,w hich can cross in the more anterior callosum, and other types of visual representationsm ay not be convertible.T hird, some visualr epresentationsm ay be associatedw ith linguisticf orms in the right hemispherea, nd othersn ot. Geschwind( 1965)o pts for the secondo f thesea nalyses.G eschwind's analysiso f the retaineda bility to nameo bjectsc laimst hat the patientsr etain this ability becausev isually presentedo bjects arousec omplex associations in other modalitiesi n the right hemisphereT. hus, presentedw ith a picture of a pieceo f fruit, for example,a patient w<>uldb e able to associateta ctile, gustatoryo, lfactory,a nd other sensoryq ualitiesw ith the visuals timulus. Thisa ssociationo f sensoryq ualitiesc onstitutest he mental representationo f the object in Geschwind'st heory, as we have seen.T he representationso f qualitiesi n other modalities can be transmitted to the left hemispherev ia more anterior-portionso f the corpus callosum. Geschwindc laims that, to a first approximation, it is only those visual stimuliw hich are linguistics ymbolsw hich cannot passf rom the right to the left hemispherew hen the spleniumo f the callosumi s damaged.T hey. presumably,d o not arouse associationsi n other modalities in the right hemisphered irectly, but require the activation of the auditory represen- tations of words in the left hemisphere to intervene in the process of activatingth esea ssociations. This will accountf or object naming- but what about namingn umbers? Geschwindc onsiders the ability to name numbers to be different from readingw ords and letters,b ecausen umbersa re overlearned.T his allowsf or

75 Il Clinical aphasiology and neurolinguistics their being associatedw ith other representationsi n the right hemisphere establishr elationshipsb etweenp which passt o the left hemisphere.G eschwinds uggeststh at the fact that we graphemes or letters - and par learn to count on our fingers suggestst hat these representationsa re phonemes. When other relationr somesthetic.T his type of analysisc an apply to certain linguistic items as phonological representatione xis well. It has been noticed, for instance,t hat when thesep atientsc an read a stimulust o the entirety of the phc little. they havea greatera bilityt o readw ordsw hicha rec oncretea ndh ighly can transmit theser epresentation picturable, and which are rich in associationsto other modalities.T hey have We have introducedt his lengtt the most trouble with the grammaticalw ords of Indo-European languages alternatev isuals tructuresa ndp at (prepositions, articles, determiners, and so on) which do not have these Whether Geschwind'sa nalysiso 'fhere qualities. are also reports that words which customarily appear on retained abilities is correcto r nol public buildings can be re'adw hen presentedo n cards. Geschwind argues Chapter 14), the analysisis a goo that these words are associatedi n a very direct way with the cognitive make use of the concepto f alter representationso f the iternso n which they appeari n ordinary life, and that reading words, letters.a nd numb -the these cognitive representationsc an be passedf rom the right to left entirely left-hemisphere-baseadc, hemisphere. is not available.a lternater outesn We have indicated that some patientsw ith alexia-without-agraphiac an are not normally gearedt o theseI read individual letters.T his does not fall under the explanationsa bove, or not at all. Thusc olors- non-lin1 sincel etters have no associationsin other modalities.T he preserveda bility - cannot be named at all. Words to read letters in some patients thus requiress ome other explanation. An depending upon the natureo f the interestingf inding hasb een that what can be readd ependsu pon the form of treated. Numbers and othera bstri orthography in which it is represented.T hus, in languagess ucha sJ apanese into other representationaflo rms which haveb oth a syllabics cript( Kana). in whichw rittens ymbols.stanfdo r languagea reas,a s may occurw itl individualsyllablesa, nd alsoa n ideographics cript( Kanji), in whichw ritten these patterns may reveal the 1 symbolss tandf or entire words, patientsw ith this syndromer etain the ability registeringa nd transmittingp artic to read the ideographic form of writing, but lose the ability to read the representations. syllabicf orm (Sasanuma nd Fujimura 1971).T his patterns uggesttsh at the Geschwind points out that sucl particularw ritten linguistics ymbolsw hich cannotc rosst he callosumi n this sameg roupingso f linguisticit ems syndrc-rmaer e thosew hichc orrelatew ritten symbolsw ith individuals ounds: other words, may havem ultiplem syrnbols which are relatcd to the sound of a word as a whole can be some of which correspondt o (or transferredf rom right to left. Patientsw ho can read lctters (name them and normative theory of languages tru< indicatet heir soundv alues)m ay be treatingt hem ase ntireu nits.W hen they duplicateo r back-ups ystemsa, nd are embccldedw ithin worcis.t hey losc this propertya nd can no krngerb e of linguistic entities describedi read. discovery of these alternatem ech 'Ihe analyseso f the different "exceptions" to the inability to name studying pathologicalm aterial,f c visuallyp resenteds timulii n alexia-without-agraphaiare thusn ot identical. isms are so efficient that these For object and number naming, the preservationo f function is saidt o reflect processesd o not emerge.I n additi right-hemispherea ssociationsF. or letter naming and readingK anji, the injured patientsa llowsu st o deterr deficit in alexia-without-agraphias seena s one whtch disturbst he trans- are involved in processingth esea mission of particular types of written linguistic representationsf rom the Thus, modern connectionismh , right visual-associationc ortex to the left-hemispherel anguagea reasa cross century analyses.I t presentsm o the spleniumo f the corpusc allosum.T heser epresentationsa re thosew hich aspectso f languagep rocessinge, r

l6 Extensi o ns of con nec tionis m establishr elationshipsb etween parts of the orthographic representation- graphemes or letters - and parts of the phonological representation- phonemes. When other relationshipsb etween the visual stimulus and its phonological representatione xist, which relate the entirety of the visual stimulust o the entirety of the phonologicalr epresentation,o ther pathways can transmit theser epresentations. We have introduced this lengthy analysisi n relationshipt o the idea that alternate visual structures and pathways may affect an aphasicp erformance. Whether Geschwind's analysiso f alexia-without-agraphiaa nd associated retained abilities is correct or not (and we shall reconsidert he question in Chapter 14), the analysisi s a good example of how modern connectionists make use of the concept of alternate pathways. The normal pathway for readingw ords, letters, and numbers, and for naming colors and objects, is entirely left-hemisphere-baseda,c cordingt o this theory. When this pathway is not available,a lternater outesm ay mediatet hesef unctions.T heser outes are not normally gearedt o thesef unctions,a nd carry them out inefficiently or not at all. Thus colors- non-linguistici temsw ithout non-visuala ssociates - cannot be named at all. Words can be read under specialc ircumstances, dependingu pon the nature of the orthography and how the orthographyi s treated.N umbers and other abstractn on-linguistics ymbolsm ay be recoded into other representationalf orms and theset ransmittedt o left-hemisphere languagea reas,a s may occur with visually presentedo bjects.T he study of these patterns may reveal the particular role of parts of the brain in registeringa nd transmittingp articularf orms of linguistica nd non-linguistic representations. Geschwindp oints out that such analysesd o not necessarilyp rovide the sameg roupingso f linguistici tems that linguistict heory does. The brain, in otherw ords, may havem ultiple mechanismsfo r analyzingl inguistics timuli, someo f which correspondt o (or make use of) natural groupingsw ithin a normativet heory of languages tructurea nd processinga, nd othersw hich are duplicateo r back-up systems,a nd which do not correspondt o the grouping of linguistic entities described in contemporary linguistic theory. The discoveryo f these alternate mechanismsi s one of the great advantageso f studyingp athologicalm aterial, for the normal human processingm echan- isms are so efficient that these alternate groupings and psychological processedso not emerge.I n addition, of course.t his detaileds tudyo f brain- injuredp atientsa llowsu s to determinew hat areasa nd pathwayso f the brain arei nvolved in processingt hesea lternativeg roupingso f representations. Thus, modern connectionismh as gone considerablyb eyond nineteenth- century analyses.I t presents more detailed hypothesesa bout particular aspectso f languagep rocessing,e mphasizesth e contribution that studieso f '77 II Clinical aphasiology and neurolinguistics pathologicalp opulationsc an make to the discoveryo f alternatem echanisms for language representationa nd processing,a nd is more rigorous in its 6 commitment to specific neuroanatomical basesf or the processesi t postu- lates. Modern connectionism has enormously influenced neurolinguistic theory, especiallyi n establishingt he framework for investigatingt he ana- Obiectionst o connection tomical basiso f languagea nd languageb reakdown with new radiological techniques (see Part IV). We shall take up the influence of modern connectionism upon the classification of the aphasias again in Part III (Chapter 11), and we shall return to many "connectionist" analysesw hen we consider psycholinguistica nalysesi n Part IIl. We shall have a better The classicacl onnectionistth eon perspectiveo n connectionism,h owever, after we considero bjections and their critics. Indeed, it is an indr alternativest o this approach. We now turn to theseo ther approaches.W e subjectt o so many attacks;u niml shall try to put both connectionisma nd other clinicalt heoriesi nto perspec- the debatea boutc onnectionismt tive in Chapter 10. over a century. Somer econstruc aphasiologicalr esearche ssential tionships into two groups- the , tionists are the prime examples virtually all other investigators. S U G G E S T I O N S F O R F U R ' I H E R R E A D I N G there are many aspectso f the co Benson, D. F. (1979).A phasia,A lexia, Agraphia. Churchill Livingstone,N ew York, ch. I l. ment to certain linguistica nd ps, Geschwind, N. (1965). Disconnection syndromcs in animals and man. Brain 88,237-94: were taken over by at leasts ome -s8-s-644. instances (1969). Problems in the anatomicalu nderstandingo f the aphasias.I n A. Benton (ed.), such as the "concept Contributions to Clinical Neuropsychology. Aldine, Chicago. aspectso f the connectionismt ode Mesulam. M. (ed.) (1985\. Principles of Behaviorol Neuroktgy. F. A. Davis, Philadelphia. as has been stressedb y Geschwin Morton, J. (1984).B rain-bascda nd non-brain-basedm odelso f language.I n D. Caplan, A. R. the connectionistsa bout the p: Lecours, and A. Smith (eds.), Biolo1;icul Perspecliveso n Lunguage. MIT Press, Cam- bridse. Mass. processing,t hey were largelyi n a and pathologicald eterminantso l error to group together all thosr since there are a varietyo f positir However, despitei ts being mi history of aphasiologya nd neurol viewpoints, largely differing or functioning of a languagef acult localized centers for particular lar is a reasonableg enerald escriptio theoreticala ttentioni n the first1 C the centrality of this issuei n tht severalc haptersi n part II to the a thought. In this chapterw e shall Sigmund Freud (1891)a nd Henr largely be seena sc riticismso f thr 78 6

Obiections to connectionism

The classicacl onnectionistt heoriesd escribedi n Chapter4 were not without their critics. Indeed, it is an indication of their importance that they were subjectt o so many attacks;u nimportant theoriesa re ignored.I n many ways, thed ebatea bout connectionistm odelsd ominatedn eurolinguistict heory for over a century. Some reconstructionso f the history of neurolinguisticsa nd aphasiologicarl esearche ssentiallyd ivide theorieso f language-brainr ela- tionshipsi nto two groups - the "localization" camp, of which the connec- tionists are the prime examples, and the "holist" camp. which includes virtually all other investigators.T his dichotomy is over-simplified.F irst, there are many aspectso f the connectionistm odels, such as their commit- ment to certain linguistic and psycholinguisticle velso 1'description,w hich weret aken over by at leasts ome of their critics.S econd,a s we have seeni n instancess uch as the "concept center" postulated by Lichtheim, not all aspectso f the connectionistm odelsw ere thought to be localized.M oreover. ash asb eens tressedb y Geschwind( 1964),t hough the criticsd isagreedw ith the connectionistsa bout the psychologicaln ature of language and its processingt,h ey were largely in agreementa bout the nature, classification, and pathologicald eterminantso f languageb reakdown. Moreover, it is an error to group together all those who disagreedw ith the connectionists, sincet here are a variety of positionsw hich theset heoristsm aintained. However, despite its being misleadingi n these ways, the view that the historyo f aphasiologya nd neurolinguistict heory was marked by two major viewpoints, largely differing on the issue of the extent to which the functioningo f a language faculty could be seen as the result of several localizedc entersf or particular languagef unctionsc onnectedt o eacho ther, is a reasonableg enerald escriptiono f what was probably the major focus of theoreticaal ttention in the first 100y earso f work in this field. It is becauseo f the centrality of this issuei n the history of the field that we shall devote severacl haptersi n Part II to the alternativesa nd objectionst o connectionist thought.I n this chapter we shall considert he work of two investigators- SigmundF reud (1891) and Henry Head (1926)- whose contributions can largelyb e seena s criticismso f the connectionists chool.O ur review of their 79 6

Obiectionst o connectionism

The classicacl onnectionistt heoriesd escribedi n Chapter4 were not without their critics. Indeed, it is an indication of their importance that they were subjectt o so many attacks;u nimportant theoriesa rei gnored.I n many ways, thed ebatea bout connectionistm odelsd ominatedn eurolinguistict heory for over a century. Some reconstructionso f the history of neurolinguisticsa nd aphasiologicarle searche ssentiallyd ivide theorieso f language-brainr ela- tionshipsi nto two groups - the "localization" camp, of which the connec- tionists are the prime examples, and the "holist" camp, which includes virtually all other investigators.T his dichotomy is over-simplified.F irst. there are many aspectso f the connectionistm odels, such as their commit- ment to certain linguistic and psycholinguisticle velso f description,w hich weret aken over by at leasts ome of their critics.S econd,a sw e have seeni n instancess uch as the "concept center" postulated by Lichtheim, not all aspectso f the connectionistm odelsw ere thought to be localized.M oreover, ash asb eens tressedb y Geschwind( 1964),t hough the criticsd isagreedw ith the connectionistsa bout the psychological nature of language and its processingt,h ey were largely in agreementa bout the nature, classification, and pathologicald eterminantso f languageb reakdown. Moreover, it is an error to group together all those who disagreedw ith the connectionists, sincet here are a variety of positionsw hich theset heoristsm aintained. However, despite its being misleadingi n these ways, the view that the historyo f aphasiologya nd neurolinguistict heory was marked by two major viewpoints, largely differing on the issue of the extent to which the functioning of a language faculty could be seen as the result of several localizedc entersf or particular languagef unctionsc onnectedt o eacho ther, is a reasonableg enerald escriptiono f what was probably the maj or focuso f theoreticaal ttention in the first 100y earso f work in this field. It is becauseo f the centrality of this issue in the history of the field that we shall devote severacl haptersi n Part II to the alternativesa nd objectionst o connectionist thought. In this chapter we shall considert he work of two investigators- SigmundF reud (1891) and Henry Head (1926)- whose contributions can largelyb e seena s criticismso f the connectionists chool.O ur review of their

79 II Clinical aphasiology and neurolinguistics reservationsr egarding the theories we have been considering up to now will one of the pathways betweent he vir alsos ervet o introduces omeo f the issuest o be taken up in Chapters7 , 8, and language center. Lichtheim sugges 9 . resolved over a period of time, and We can divide objections to connectionismi nto three main groups. The would show resolutiono f the alexia.I firstc onsistso f the claim that the basico bservationsm ade by the connection- documentedc aseso f prolongedr eadi istsw ere incorrect,o r that there were additionalo bservationsa bout aphasic aphasia, in one case for years afte performances which cast the particular theories of language-brain relation- examination in this casef ailed to rer ships advancedb y connectionistsi nto doubt. The secondg roup of objec- that this combination of deficitsc onsr tions is directed towards the logic of the connectionists'i nferencesf rom cast serious doubt on the connection aphasics ymptomst o neurolinguistict heory. Theseo bjectionsf ocus on the imagine any model along connection theory without disputingt he actualo bservationsa bout aphasiam ade by the combination of deficits. connectionists. The third set of objections consists of the view that A secondc riticismw hich Freud lel neurolinguistic theory should be based upon a different set of observations relation to a cased escribedb y Grashe about the behavior of aphasicp atients from that which the connectionists of "anomic" aphasia. Grashey'sp al made. In this chapterw e shallb e mainly concernedw ith the first two typeso f made a few paraphasic errors in r objection; the last type will be coveredi n Chapters7 and 8. understandw hat wass aidt o him. His The work of Sigmund Freud (1891)r aisedq uestionso f the first two types and pictureso fobjects. Freud pointec regardingt he connectionista pproach. We shall first considert he issuesh e understandi ndividual words.i t mustt raisedc oncerningt he adequacyo f the connectionistd escriptions. model (Figure 4-3), the connectionsfi Freud did not dispute the level of empirical description in the work of form of words in Wernicke,sa reat o tt Wernicke (1874)a nd Lichtheim (1885);t hat is, he was willing to acceptt he that the patient had troublen aminsr view that a reasonablew ay of describinga phasics ymptomsa nd syndromes, the reversed irectionw asd isrupted],a and languagef unctions, was in terms of the entire tasks of languageu se tion flow in only one direction atong which we have seenc haracterizedt heset heories.H e pointed out, however, model to a whole range of interpret that the value of a theory such as Lichtheim's lay in its ability to predict all unwilling to incorporate.W hat would I possiblec ombinationso f symptoms.I f there were a syndromei n which the way disturbanceo f informhtionf low? grouping of symptomsc ould not be adequatelye xplainedo n the basiso f the tion from one centert o anotherd iffere connectionsa nd information flow postulatedb y the model, this would be a the reversed irection?$ o one hads ugg serious flaw in the model. Freud discussedt wo such constellationso f Aside from these questions,t here symptoms.H e concludedt hat there were seriousd eficitsi n thesem odelsi n circumstancest,h e patientc ould name general. given more time to view the object,o l The first symptom group was the combinationo f an alexia,a ffectingb oth clues, such as the classo f objectt o wh silent reading and reading aloud, with a Broca's aphasia.L ichtheim (1885) Grashey had claimed that the defic had indicated that this set of symptoms often co-occurred, and Freud particular pathway, but rather reflec stressedt hat the co-occurrence of these symptoms was too frequent to be pathways could work. Freud sugges due to chance.H e pointed out that the centersa nd connectionsp ostulatedi n patient's ability to achiever apid integ Lichtheim's model (and in severalo ther connectionistm odels) could not The ability of the patient to synthe accountf or the combination of a motor aphasiao f the Broca's type and an perceptual units which could be relat alexia. Lichtheim (1885) had anticipatedt his criticism and had suggested defective.G rasheyh ad testedt hish yp that, in casesi n which there was both an alexiaa nd a Broca'sa phasia,t here feature of the patient'sn amingd ifficul may haveb eena seconds malll esione ither in the visuall anguagec entero r in when the patient wasg iven more time 80 Objections to connectionism one of the pathways between the visual languagec enter and the auditory language center. Lichtheim suggestedt hat this lesion was minor and resolvedo ver a period of time, and predicted that, over time, these cases would show resolutiono f the alexia.F reud pointed out that there were well- documentedc aseso f prolonged readingd ifficultiesa ccompanyinga Broca's aphasia,i n one case for years after a stroke. Moreover, post mortem examinationi n this casef ailed to reveal a secondl esion. Freud concluded that this combination of deficitsc onstituteda true aphasics yndromew hich cast serious doubt on the connectionist models, because it was difficult to imaginea ny model along connectionistl ines which would accountf or this combinationo f deficits. A secondc riticism which Freud leveled againstt he connectionistsw as in relationt o a cased escribedb y Grashey( 1885),w hich fallsu nder the heading of "anomic" aphasia. Grashey's patient was able to speak fluently. He made a few paraphasic errors in spontaneous speech. He seemed to understandw hat was saidt o him. His major difficultyw as in naming objects andp ictureso f objects.F reud pointed out that, sincet he patient was able to understandin dividual words, it must be the caset hat, following Lichtheim's model( Figure 4-3), the connectionsf rom the representationo fthe auditory form of words in Wernicke's areat o the conceptc enterw ere intact. The fact that the patient had trouble naming objects suggestedth at the pathway in I the reversed irection was disrupted.A llowing for a disturbanceo f informa- tion flow in only one direction along a pathway opened the connectionist model to a whole range of interpretations which it had previously been unwillingt o incorporate.W hat would the anatomicalb asisb e for sucha one- wayd isturbanceo f information flow? Were the pathwaysc arryingi nforma- tion from one centert o another different from thosec arryingi nformation in ther eversed irection?N o one had suggestedth is possibilityi n the literature. Aside from these questions,t here were other problems. Under certain circumstancesth, e patienl could name objects.T his happenedw hen he was givenm ore time to view the object, or when he was given various semantic clues,s ucha s the classo f object to which the presenteds timulusb elonged. Grasheyh ad claimed that the deficit in this patient was not one in a particularp athway, but rather reflected the conditions under which the pathwaysc ould work. Freud suggestedt hat the difficulty lay with the patient'sa bility to achiever apid integrationo f visuallyp resentedm aterial. The ability of the patient to synthesizev isual information quickly into perceptualu nits which could be related to a semanticr epresentationw as defective.G rashey had tested this hypothesis, and discovereda n interesting featureo f the patient'sn aming difficulties:t he improvementw hich wass een whent he patient was given more time to view a drawing disappearedw hen

81 Il Clinical aphasiology and neurolinguistics

the patient was forced to look at a drawing through a smallh ole in a pieceo f might be true on a psychologicalI paper, such that he could only seea .b it of the drawing at a time. When the that the neurological basisf or t drawing wasp resentedb it by bit in this way, the patientw asn evera ble to say elementary part of the totalityo f what the object was, no matter how much time he was given. Grashey and brain and the whole word comor Freud agreed that this was due to the failure of perceptual integrative Indeed. Freud arguedt hat thii mechanismsin the visualm odality. represented. He pointed out tha Freud pointed out that this case- and, similarly, all caseso f anomic joining up of the sound and the aphasia- fell outside of the connectionistf ramework. ln this case,a ll the somehow representb oth the wor centersa nd the connectionsb etween them were intact. but the conditions within itself. Thus, thougho ne col under which a pathway could operate - in this case, some aspecto f the words were in one place and the integration of visual material by the conceptc enter- were impaired. What neuron involved in connectinst he this meant was that the deficit was functional, not anatomicali n any sense of a word with the word's so-und recognizedb y connectionism.T hese functional factors must apply to the neurons might be Iocalizedj,u st as normal operation of the languages ystem.F reud quotes with approval the associations;in this case.t he com work of Bastian (1887),a British neurologistw ho incorporateds everals uch natively. each neuron representi functional factorsi nto connectionistm odels.a s well as the work of Jackson neurons representingi ts associatic (see Chapter 7). accomplishc omplex functions. Freud thus questionedt he completenesso f the connectionistm odels;a nd Freud suggestedth at it would be ,.net,. he pointed out that Lichtheim himself had argued that these models were representedi n a sort of of ner much lessi mportant if they were incomplete.H e also arguedt hat there was and motor speecha spectso f a wor no natural way to completet he modelsw ithout introducingw hat he termed perisylvian area. Freud suggested "functional" factors;t hat is, specificationosf the manneri n which a center net, with auditory information be or pathway operated. auditory area, visuali nformationb This first set of objectionst o connectionistt heory dealsw ith the need for visual cortex. etc. In this way, tl additional psychological,o r psycholinguistic,d escriptionsi n thesem odels. koniocortices would come to be Freud's next objection dealt with the neurologicalb asisf or the functionst he representations,w ithout there beir connectionistsp ostulated.F reud arguedt hat the conclusiont hat elementary and a "connecting pathway". Freu functions,'int he connectionists ense,a re localizedi n centers,w hile complex breakdown that occurrgda fterd istr functions are built up by connectingc enters,d oesn ot follow from the facts in connectionist models did not of aphasiaa nd, in fact, is an erroneousv iew. suggestedt hat the evidencef rom la Freud argued that it was incorrect to assume that an "elementary" as showing that centers and con: psychologicalf unction was related to a cerebrall ocalization,w hile a "com- difference between the types of sy plex" psychologicalf unction was the result of the interaction of different what connectionistss aw as ,,centt brain regions. Freud chose as an example the nature of individual words. with Freud's neurolinguisticth eory Freud suggestedt hat each word consistedo f a sound pattern and a set of Freud's work was not widely r associations- the latter largelyr elatedt o the sensoryq ualitieso f the objects ignored. Howcver, a volume whic in the real world to which the word referred. Freud pointed out that the approachest o neurolinguisticm od connectionistsw ould considert he soundp attern of the word and eacho f the Henry Head's Aphasia and Kindrea modality-based associations to be elementary psychological entities, Head was not merely critical of th whereas the entirety of the word would be a complex unit made up by temptuous of much of their work, . connectionsb etween thesee lements.H owever, Freud argued,t hough this and connectionsa nd the developmr 82 O bj ecti ons Io conn ectio n ism

might be true on a psychological evel. its psychologicatl ruth did not imply that the neurological basis for this arrangement was one in which each elementaryp art of the totality of a word was representedi n a region of the brain and the whole word composedo f the connectionso f these regions. Indeed, Freud argued that this was unlikely to be the way words were represented.H e pointed out that any neuron which was involved in the joining up of the sound and the associative properties of a word must somehowr epresentb oth the word's sound properties and its associations within itself. Thus, though one could postulatet hat the soundp ropertieso f words were in one place and the associationso f words in another, every neuroni nvolved in connectingt he representationo f an associatedp roperty of a word with the word's sound must have both representations.T hese neuronsm ight be localized,j ust ast hoseo nly representingt he soundo r the associationsi;n this case,t he complex function would be localized.A lter- / natively, each neuron representing a word's sound could be linked to neuronsr epresentingi ts association.I n this case,a ll these neurons would accomplischo mplexf unctions. Freuds uggestedth at it would be reasonableto assumet hat eachw ord was representedin a sort of "net" of neurons.T he auditory, visual,s omesthetic, andm otor speecha spectso f a word were all representeda crosst he entire perisylviana rea. Freud suggestedt hat there might be gradientsw ithin this net, with auditory information being more densely representedn ear the auditorya rea, visual information being more denselyr epresentedn ear the visual cortex, etc. In this way, the associationc ortex near the primary koniocorticesw ould come to be specializedw ith respect to linguistic representationsw, ithout there being a strict differenceb etweena "center" anda "connectingp athway". Freud also arguedt hat the types of language breakdownt hat occurred after disturbanceo f "centers" and "connections" in connectionist models did not differ from each other, and he thus suggestetdh at the evidencef rom languagep athologys hould be interpreted as showing that centers and connections did not exist. The lack of a differenceb etween the types of symptom which occurred after lesions of what connectionistss aw as "centers" and "connections" was consistent with Freud'sn eurolinguistict heory. Freud's work was not widely read, and his arguments were largely ignored.H owever, a volume which did exert a great influence over the approachetso neurolinguisticm odels and the description of aphasiaw as HenryH ead's Aphasia und Kindrecl Disorders of Speech,p ublished in1926. Headw as not merely critical of the connectionists;h e was blatantly con- temptuouso f much of their work, referring to the proliferation of centers andc onnectionsa nd the developmento f theory in this field as "chaos". In 83 ll Clinical aphasiology and neurolinguistics underlyingl anguaged isturbance what is certainly the most widely read section of his two-volume book on needed to explain aphasics ymp aphasia, the historical survey of aphasiology, he sums up the group of impairmentsc ouldb ed escribeidn "diagram makers" as follows: discussinHg enschen'(s1 920l)o ca Most of the observersm entionedi n this chapterf ailed to contributea nythingo f the fullest and most detailedr eports 'pdeormmiannaetendtv aluet o the solutiono f the problemso f aphasia... . becauseth ey were by a philosophicalf allacy of their day. They imaginedt hat all vital patientm ay haveb eena blet o carry processesc ould be explainedb y some simple formula. with the help of a few morec omplexh; ec ouldr eadw ithu nd iarefully selecteda ssumptions,t hey deduced the mechanismo f speech and a commandto act:o r hec ouldw riteh i embodiedi t in a schematicfo rm. From diagramsb, asedo n a priori principles,t hey tabulateda so neo f "word-deafness," deducedi n turn the defectso f function which must follow destructiono f each "centre" or internuncialp ath. They neverd oubtedt he solidityo f their postulates, Nor is he optimistic about a lingu baseda st hey were on the rule ofhuman reason.T hey failedt o appreciateth at the ance; on the contrary, he mainta logicalf ormulaeo f the intellectd o not corresponda bsolutelyto physicael ventsa nd adequatelye xpressedin termso f exercisefo r the humanm ind. (Head \926 65) thit the universed oesn ot exista sa n can be dissectedin to grammatical The second Interestinglye nough, Head's own work is rarely cited today, and despite set of observations tion, classification,a nd explanatir his enormous influence in discrediting the connectionist approach, it is Aphasic symptomsa re transient, uncertain how much he himself left of permanent value in this field. In i positive terms, he did much to reintroduce the work of Jackson into It is a commono bservatioinn the be conceptual and empirical approaches to aphasia and language-brain rela- could be executedw ith ease.w hich surroundingsfr,i endlyp eoples, ympa but whether his own thinking went much beyond that of Jack- tionships, have a profound effect on the resu son's, or whether he merely rephrasedi t, is not very clear. His criticisms, neglected(.8 3) however, are well worth reviewing. Aside from this day-to-dayv ariat Head was a greato bservero f detail, and, if there is a way to summarizeh is variation in the abilitieso f differ discomfort with the connectionistsa, nd with other workers, it might well be - universalt endencyf or aphasics yn to sayt hat he took them to task for ignoringt he detailso f aphasia.H e called direction of becomingl esss evere for,,a ruthless destruction of false gods", by which he was referring to describea patiento r a syndrome, "theoretical assumptions,b oth positive and negative", and "a return to lesion in brain? Chaos-indeed. systematice mpirical observation of the crude manifestationso f disease" It is fair to say that neither Her (Head 1926:66). It is impossible to do justice to the richness of his these issues.H ead proposeda Ja, descriptionso f aphasicp atientsi n a few lines, and that is not our aim here. symptoms, but it is far from clei Rather, we shall focus on features of aphasic performance which he consider in the next chapter,a deq reported, and which he felt could not be accommodatedw ithin connection- tions. Head used these observat ist models. It is important to considert hesef eatureso f aphasiai n relation to centers responsiblef or languageI other theories we shall encounter, and to ask whether they are better disease,a nd we may acceptt he fr integrated into any other type of model. Of the many features Head time, appreciatingt hat it appliest describes,w e shall review two, which are arguably those he was most As with Freud. Head did not or concernedw ith. also attackedt he concepto f a cent The first observation is that aphasic performances cross descriptive on a physiologicalb asis.F reud'si boundaries. We have seen how the connectionistse stablishedd iagnostic Head's is more direct, being base, categorieso n the basis of the relative impairments seen in the tasks of stimulation of cortical structure language use; and we have already seen that Freud argued that more experirnentalp rocedures. detailedd escriptionso f the qualitativen atureo f the psychologicapl rocesses

84 O bj ections to connectionism

underlying language disturbances indicated that functional factors were needed to explain aphasic symptoms. Head also denied that language impairmentsc ould be describedi n terms of the totality of languaget asks.I n discussingH enschen's (1920) localizations, for instance, he remarks that the fullest and most detailedr eportsc annotb e summarizedin tabular form. The patientm ay haveb eena blet o iarry out simpleo rders,b ut not thosew hichw ere morec omplexh; ec ouldr eadw ith understandinpgr, ovidedth ew ordd idn otc ontain a commandt o act:o r he couldw rite hisn ameb ut not hisa ddressC. ans ucha caseb e tabulateda so neo f "word-deafness","a lexia,"o r "agraphia"?( Head1 926:83)

Nor is he optimistic about a linguistic analysiso f the patterns of perform- ance; on the contrary, he maintains that "Defects of languagec annot be adequatelye xpressedi n terms of parts of speech. . . no variety of aphasia canb e dissectedin to grammaticael lements"( 121). / The second set of observationso nly compound the problem of descrip- tion, classification,a nd explanation of aphasics ymptoms and syndromes. j Aphasics ymptomsa re transient,i ndeed ephemeral. It is a commono bservationin the besto bservedc asesth at on a certaind ay tasks could be executedw ith ease,w hich were otherwiseq uite impossibleF. amiliar surroundingfsr,i endlyp eople,s ympathetihca ndlinga ndt he modeo f examination havea profounde ffect on the resultso btained,a fdct which has been widely neglected(8. 3)

Aside from this day-to-dayv ariation within a single patient, there is wide variation in the abilities of different patients with similar'lesions, and a universalt endencyf or aphasics ymptomst o changeo ver time, usuallyi n the direction of becoming less severe, in vascularc ases.H ow then are we to describea patient or a syndrome,a nd to relate the functional disabilityt o a lesioni n brain? Chaos indeed. It is fair to say that neither Head nor any other theorist has answerst o thesei ssues.H ead proposed a Jacksonianf ramework for viewing aphasic symptoms,b ut it is far from clear that that framework, which we shall consideri n the next chapter, adequatelyd ealsw ith theset ypes of observa- tions. Head used these observationsa s evidence against the notion of centersr esponsiblef or languaget asks, which were individually subject to diseasea, nd we may acceptt he force of this argument while, at the same time, appreciatingt hat it appliest o many qther neurolinguisticm odels. As with Freud, Head did not only dispute the analysiso f symptoms;h e alsoa ttackedt he concepto f a centera nd that of the localizationo f functions on a physiologicalb asis.F reud's argument was indirect, as we have seen. Head'si s more direct, being basedo n observationsr egardingt he effect of stimulation of cortical structures in animals by electrical currents in experimentapl rocedures. u5 lI Clinical aphasiology and nettrolinguistics

Head pointed out that experimentale lectricals timulation of very small a successiono f synergic movementt areas of motor cortex yielded patterns of motor activity which were hard to segments,t his is impossible;w e are functions. The complete act reconcile with the notion of a strictly localized function. Stimulation of in its pe sequenceo f a serieso f - complexp rocr motor cortex produces very discrete movements usually flexion or exten- Monakow layss o much stressi.s of fun sion of one joint. This might be considereda paradigmatic example of cal exactitude will throw the whole m localizationo f a simple function. However, Leyton and Sherrington( 1917) has been destroyed. Here there can be no question had shown that, in apes, the effect of stimulation of a point in the motor of a fo, of the necessaryp aths of innervatione cortex is not constant, but varies with prior stimulation. Rapidly repeated centres. But, on the other hand.a ll act stimulation of a given point in the motor cortex usually increasest he be interrupted by a lesion of the sur amplitude of a particular movement at a joint; but if a point is stimulateda t "localised" within its boundaries.( 88) greater temporal intervals, both the charactero f the response( flexion as Head thus denies the validity opposedt o extension)a nd the location ofthe response( one joint insteado f localization of parts of the t another) may changeo n occasion.S imilarly, if tissuei s removed from the bodl I Functional localization in the motor cortex. a deficit in movement occurs and recoverso ver a period of comtr functions" is akin to motor time. If the cortex in the region of the ablation is stimulateda fter recovery functio has occurred. the previous movement does not occur in all circumstances. Thus, all these primitive functions,m r Nor doesr emoval of a greatera mount of tissuei n the region of the previous affected independentlv from different excisionn ecessarilyc auset he deficitt o reappear.T his suggeststh at the area situation ofthe functionald isturbanceir of the lesion within anv one of thesea r in question is not organized so that adjacent areast ake over a particular Disorders of speech. or defectso f motor movement. Finally, Head mentions experimentsw hich show that destruction of the brain. differ from thr excisiono r stimulation of "sensory" regions,i n particular the post-central that there is no suchr elationt o partso ft gyrus, can greatly influence the effects of stimulation in the pre-central the lesion to be effectivem ustb es ituatc level the problem of "cerebral localise "motor" gyrus.T hesep henomenao f reversalf.a cilitation,a nd deviationo f and is greatly increasedi n complexity. response to electrical stimulation provide evidence of "functiclnal task of associatings ome focuso f destr instability" in the cortex not in keepingw ith a simple notion of localization definite part of the body or visualf ield. of elementaryf unctions. more difficult question:W hat form doe lesion? We must first distinquishc ate Despite these observations,w hich indicate that the neurophysiological languagea nd thena trempt, .iu asp oss basisf or functional locatlizationis complex. Head was wilting to acceptt he of the lesion in the left hemisphere(. 4: view that the concepto f functional localizationi s applicablet o somea ctions and perceptions.A t the very least,h e acceptedt he notion of the topographic Head thus emphasized the differ representationo f parts of the body, to the extento f agreeingt hat areass uch which, if not strictly localized, at asf ace, hand, and arm stood in a constantr elationshipt o eacho ther. On the relation to each othcr. motor and s other hand. functions, as opposed to topographicalr elationshipsb etween components and which are thus no parts of the body. were not localizedi n his view: are similar to motor or sensory fun differ inasmuch as they do not Theo nlyf ormo f anatomicalol calisatiown hichc anb eu nhesitatingalyc cepteids t he ev, relativet opographicirrle presentatioonf the variousp artso f the body. We can Head recognized that it is a very g confidentlay ssumea st her esulto f physiologiceaxl perimenatn dc linicaol bservation functional components of motor ar that,f or instancet,h e face,h and,e lbowa nds houldesr tandi n a definiter elationt o intellectual processes, as opposed onea nother.a lthoughth e resultso f stimulatinga nyo nep ointo n thes urfaceo f the topographic projections. Like hrainm ayv aryf romt imet o time. Freu We cand iscovetro a limitedd egreefo calc entresfo r certains imples imultaneous sion of language functions into fa musculaar ctionsin somed efinitep arto f theb odv.B ut.w henw ea ttempt o dealw ith comprehension, and so on. eacht as

86 Objections to connectionism

a successiono f synergic movements and alternating changes in the limbs or segments,t his is impossible; we are face to face with an interrelation of diverse functions.T he complete act in its perfect form demandst he mobilisation in due sequenceo f a serieso f complex procedures;h ere the time relation, on which von Monakow lays so mydh stress,i s of fundamental importance. A want of chronologi- cal exactitude'w'ililh row the whole movement into'disorder; its "kinetic melody" hasb een destroyed. Here there can be no question of a focal localisation of function, even though many of the necessaryp aths of innervatione mergeh ere and there from definablei nsular centresB. ut, on thero ther hand, all actionsw hich contain a corticalc omponent can be interrupted by a lesion of the surface of the brain, although they cannot be "localised"w ithin its boundaries.( 88)

I' Head thus denies the validity of any parallel between topographic I localization of parts of the body and localization of motor functions. ) in psychological "higher /l Functional localization the complex domain of the t , functions" is akin to motor function. and is itlso not localized: I Thus,a ll thesep rimitive functions, motion, sensationa nd vision, can not only be affectedi ndependentlyf rom different parts of the surface of the brain, but the situationo f the functionald isturbancei s associatedto pographicallyw ith the position of the lesionw ithin any one of these,areas. Disorderso f speech, or defects of similar high-grade functions, due to local destructioonf the hrain,d ifter from thoseo f motion,s omatics ensationo r visioni n thatt herei s no suchr elationt o partso f the body or its projectioni n space.M oreover, thel esiont o be effectivem ust be situatedi n one definiteh emisphere. . . On this high levelt he problem oi "cerebral localisation" acquiresa somewhatd ifferent aspect andi s greatlyi ncreasedin complexity. We no longer have the comparativelys imple tasko f associatings ome focus of destructioni n the brain with losso f function in a definitep art of the body or visualf ield. but are compelledt o ask ourselvest he much mored ifficultq uestion:W hat form doesi t assumci n accordancew ith the site of the lesion?W e must first distinguish categoricallyt he various defects in the use of languagaen d then attempta sf ar asp ossiblet o determinet heir relationt o the locality of the lesioni n the left hemisphere.( 43tt)

Head thus emphasized the differences between topographic projcctions, which, if not strictly localized, at least bear a constant neuroanatonlical relation to each other, motor and sensorlt functions, which are made up of components and which are thus not localized, and higher functions, which are similar to motor or sensory functions in that they are not localized but differ inasmuch as they do not even projcct topographically onto space. Head recognized that it is a very great challenge to describe correctly the functional components of motor and sensory capacities or those of higher intellectual processes, as opposed to determining the neural locations of topographic projections. Like Freud, Head explicitly denies that the divi- sion of language functions into faculties devoted to speech production, comprehension, and so on, each task coupled with a single linguistic level of

87 II Clinical aphasiology and neurolinguistics

representation,w as adequate.H e thus rejectedb oth the psychologicala nd neurologicalc laimso f the connectionists. 7 It is inaccuratet o view the work of Freud and Head as entirely critical. The observationse achm ade were alsod irectedt owardst he developmento f other theories, in both the area of characterization of abnormal function and Hierarchical models performance deficits and in that of defining neurological mechanisms.M any of their positive suggestionsa re closelyr elated to the theories of workers whose contributions we shall come acrossi n the next two chapters.T he presentc hapter utilizesp arts of their work to indicates ome of the forms of disagreementw ith the connectionista pproachw e have presentedi n Chap- In the previous chapter, we h: ters 4 and 5. Having establishedt hat the connectionistt heoriesa re not the completely suret hat the waylan6 whole answer,a nd certainly not the only possiblem odel of language-brain a number of centers. each resl relationships,w e now turn to a number of other approachesa nd conceptual function in a particular areao f th / frameworks for neurolinguistict heorv. matter. But if this is not the neurolinguistics,w hat is?I n thisa three other approachesto model which answerst his questions omt S U G G E S T I O N S F O R F U R T H E R R E A D I N G consider models which view both considering behaviort o be the re (1964).T he paradoxicalp osition of Kurt Goldsteini n the history of aphasia. Geschwind, N. of the nervouss ystem,r athert ha Cortex 7. 214-24. Marshall, J.C. (1974). Freud's psvchologyo f language.I n R. Wollheim (ed.), Freud: A simple components. In Chapter Collection o.f Critical Essays.A nchor Books, Garden City. linguistic (and other) behavior nervous system,a nd the psyche,a examine modelsi n which noneo f psychologicalf unction. In eachc t of the particular approach,w e sha of the approach. and the waysi t r John HughlingsJ acksonw aso neurology. and, along with Wi neurologist of his day. Among languaged isordersa nd their ana' symptoms, and to the neurologic symptomatology,s tandsin marke localization modelsw e havec ons writings on aphasiaa nd language- his having been influencedb y the we know that he was familiar wi various questions about aphasii published in Brain, of which Jac work is so much a product of his from that of other workers of his 88