Neurolinguistics and Linguistic Aphasiology: an Introduction
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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 <lf the inferior frontal c<lnvolutionB. roca punctured the cyst, releasingir smallq uantityo f fluid. He then piercedt he brainu nderlyingt he cystw ith a probe.T he brain wass oftcrt han it shouldh aveb een.A s Broca passedt he probe posteriorly, the softncsse xtendedi nto the region of the parietal operculum (the area above the Sylvian fissure),a nd Broca found that the brainb ecamem orc norrnali n consistencays t he probem ovedm clre posteriorly.T hc softeninge xtendcda nteriora nd medial to the cyst for a shorterd istanceth an it dicli n the postcriord irection.T he lesioni si llustrated i n F i g u r e3 - 1 . Broca analyzcdt he casea ccordingt clt he traditionalr nethodo f clinical- anatomicalc orrelation.H e diviclcdt he illnessi nto threes tages.I n the first stage,l astinga houtt en years.t hc paticnth ada lesiona t thes o-called"f irot" ofthe third frontal gyrus,a nd sulteredf rom an isolatedd eficiti n language. In the seconds tage,t he lesiona ffcctedt he adjaccntm otor strip. and the patientd evelopeda paresiso fthe right arm and face.I n the third stage,t he lcsionp enetratcdm orc posteriorlya nd widcly, and the patientd evelopeda paralysiso f the right leg. Accorclingt o this analvsisi,t was during the first stage,w hcn the lesiono ccupiedt he foot of the third frontal convolution, that an isolatedd eficiti n languagew asm anifest. Brocat hen suggesteda n analysiso f the languagea bnornralitya, nd of the factors in the brain which prcduced it. The analysiso f the languaged isorderc onsistedo f dividingc ommunicative 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 apparent ability 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.