Electrophysiological Evidence for Early Contextual Influences During Spoken-Wordrecognition: N200 Versus N400 Effects

Electrophysiological Evidence for Early Contextual Influences during Spoken-WordRecognition: N200 Versus N400 Effects

Danie¨lle van den Brink,Colin M.Brown, andPeter Hagoort

Abstract

& Anevent-related brainpotential experiment was carried findingan N400 effect inthe two semantically anomalous out to investigate the time course ofcontextual influences on conditions, we obtained an early negative effect inthe spoken-word recognition. Subjects were presented with semantically anomalous condition where wordonset differed spoken sentences that ended witha wordthat was either fromthat ofthe congruent completions. It was concluded (a)congruent, (b)semantically anomalous, but beginning that the N200 effect isrelated to the lexical selection process, withthe same initialphonemes as the congruent completion, where word-forminformation resulting froman initial or(c) semantically anomalous beginning withphonemes that phonological analysis and content informationderived from differedfrom the congruent completion. In addition to the context interact. &

INTRODUCTION modelsassuming a highdegree ofinteractivitybetween Ineveryday speech,people hear wordsin thecontext of contextual and acoustic information,and other models other words,usually in the form of sentences. Inthe assigningpriority to the acoustic analysis.A keyissue literature on language comprehension,there isevidence here concerns therelative momentin time at which tosuggest thatcontextual influences playa role inthe context startsto exert an effect on word recognition. on-linerecognition of spokenwords (Salasoo &Pisoni, The present studywas designed toinvestigate thetime 1985; Marslen-Wilson& Tyler,1980; Morton, 1969). In course of contextual effects on spoken-wordrecogni- therecognition ofwordsspoken in isolation, a number tion.The focus of our studyis on theelectrophysiolog- of spoken-wordrecognition modelsconverge on the ical manifestation of these effects, and lesson the idea thatmultiple lexical candidates thatshare word empiricalseparation of competing word recognition onset are accessed on thebasis of an analysisof the models.We seek tovalidate an early electrophysiological initialphoneme(s) of aword (McQueen, Norris,& manifestation of theprocessing interface between words Cutler, 1994; Norris,1994; Norris,McQueen, &Cutler, and theircontext, whichwill provide a real-time meas- 1995; Goldinger, Luce, &Pisoni,1989; Goldinger, Luce, ure withwhich to test competing spoken-wordrecog- Pisoni,& Marcario, 1992; Marslen-Wilson,1987; Marslen- nitionmodels. Wilson& Welsh,1978; McClelland &Elman,1986). As Event-related potentials(ERPs) reflect the sumof pronunciationof aword progresses over time,lexical simultaneouspostsynaptic activity of alarge numberof candidates are dropped as soonas theyno longer neurons recorded at thescalp as small voltage fluctua- correspond tothe incoming acoustic signal.Selection tionsin the electroencephalogram. Acentral finding in of theproper candidate issaid to take place when only theERP literature on language isa negative-going com- one candidate isleft thatstill matches theacoustic ponent thattypically peaks at 400 msec after stimulus signal. onset,the N400 (cf. Kutas &Hillyard,1980). The N400 Word recognition insentences additionallyrequires component isrelated to semantic processing of the thatthe selected word isintegrated intoa higher-order eliciting word and isobserved inboth the visual and meaning representation of thesentence context. The theauditory modality. Although N400 effects have some- impactof sentential–contextual informationon therec- timesbeen related to lexical access (Kutas &Federme- ognitionprocess isa matter of debate, withseveral ier,2000), todaythe most widely held view is that in sentence contexts, the N400 amplitudeindexes the relative ease of semantic integration (e.g., Brown & Max PlanckInstitute forPsycholinguistics, Nijmegen, The Hagoort, 1993, 2000; Holcomb,1993): Words thatare Netherlands incongruent or lessfitting given thepreceding sentence

© 2001Massachusetts Institute ofTechnology Journal ofCognitive Neuroscience 13:7, pp. 967–985 frame typicallyelicit amuchlarger N400 thanwords that word,and where theydid obtain an N400. Therefore, fit well withinthe context. ThisN400 effect hasa Connollyand Phillipsclaimed thatthe early negativity posteriorscalp distribution and an onsetaround 200– was a phonological mismatch negativity (PMN),reflect- 250 msec after word onset (for reviews,see Osterhout& ing adiscrepancy between theinitial phonemes of the Holcomb,1995; Kutas &VanPetten, 1988, 1994). How- expected word and theactually perceived word.Their ever, semantic integration of theperceived word into resultsseem to supportthe notionthat a semantic thesentence context isone of thelast subprocesses in expectation of aparticular word isformed on thebasis spoken-wordrecognition. If theN400 effect solelyre- of thepreceding context. Subsequently,the incoming flects thesemantic integration process,is there any signalis matched against thephonemic template ofthe other evidence inthe electrophysiological signal that expected word.If theinitial phonemes do notmatch, a context exerts an influence priorto semantic integra- PMNiselicited. tion? Ordoes theN400 effect notonly reflect integration VanPetten, Coulson,Rubin, Plante, and Parks(1999) processes,but also early semantic processingat alevel performed astudysomewhat similar to that of Connolly where lexical and contextual informationinteract? A and Phillips(1994). In thisstudy, they made use of numberof recent ERP studieson spoken-wordprocess- informationabout theisolation points (IP) of words, ing haveaddressed these issues. namely,the minimum amount of acoustic signalneces- Connollyand Phillips(1994) carried outa studyto saryto identifya spokenword inthe absence of investigate thepossibility of theexistence of aseparate contextual information(cf. Grosjean, 1980). The IPs ERPcomponent inthe auditory modality, preceding the were establishedwith the gating technique,in which N400, that,in their terminology, might reflect somekind subjectshear increasingly longer fragments of aword, of ’’preprocessing phase’’related to contextual influen- and report after each fragment whichword theythink is ces. Inearlier studies,Connolly, Stewart, and Phillips being presented. VanPetten et al.hypothesized that (1990) and Connolly,Phillips, Stewart, and Brake (1992) ’’. . . if semantic processes begin tooperate on the hadfound anegativitypeaking at 200 msec.In their 1994 partial and incomplete resultsof perceptual analyses, study,they hypothesized that this N200 was related toa thenthe influence of semantic context mightbegin phonologicalprocess that assessed whether theinitial before theIP, as soonas theacoustic inputbecomes soundsof aword fit thesentential context. Onthebasis discrepant withsemantic expectations’’(p.397). Their of thepreceding context asemantic expectation of a experimental itemsconsisted of highto low constrain- particular word isformed, and if theinitial phonemes of ing sentences thatended either (a) withthe highest- theperceived word do notmatch the initial phonemes cloze probabilityword, (b) witha word thatrhymed of theexpected word,an N200 iselicited. The under- withthe highest-cloze probabilityword,(c) witha lyingidea isthat, certainly inthe auditory modality, the semanticallyanomalous word thatshared the same semantic systemcould benefit from suchan early proc- initialphonemes as the highest-cloze probabilityword, ess.To testtheir account of an early negativityreflecting or (d) withan anomalousword of whichthe initial aphonologicalprocess, Connolly and Phillips(1994) phonemesdiffered from thoseof thehighest-cloze included four conditionsin their design. The experi- probabilityword. For example: ’’Itwas apleasant sur- mental itemsconsisted of mediumto high constraining priseto find thatthe car repair billwas onlyseventeen sentences thatended witha semanticallycorrect or dollars/scholars/dolphins/bureaus. ’’ anomalousword. The semanticallycorrect sentence- The resultsrevealed thatthe sentence-final wordsin final wordswere either thehighest-cloze probability the three anomalousconditions all elicited asignifi- wordsand therefore theexpected endings(e.g., ’’The cantly larger N400 thanthe high-cloze probabilityend- pianowas outof tune)or wordsthat were of alower ings.Moreover, theonset of theN400 effect differed cloze probability(e.g., ’’Don caught theball with his between conditions.In the fully anomalous and rhyme glove,’’ where hand wouldhave been expected). 1 The conditions,the onset of theN400 effect preceded the semanticallyanomalous sentence-final wordsbegan with IPof thesentence-final words.Relative tothese two phonemesthat were either similarto thoseof the conditions,the onset of theN400 effect inthe con- expected word (e.g., ’’The gambler hada streak of bad ditionwhere theanomalous word shared itsphonemic luggage,’’ where luck wouldhave been expected) or onset withthe highest-clo ze probabilityword was different (e.g., ’’The dog chased thecat upthe queen,’’ found tobe delayed bysome 200 msec and corre- where tree wouldhave been expected). spondedto the IP. Itwas concluded thatthe onset of Inthe two conditions where theonset of theword did theN400 effect was related tothe moment at which notmatch that of thehighest-cloze probabilityword, theacoustic inputfirst diverged from semantic expect- Connollyand Phillips(1994) obtained an early negativity ation.Van Petten et al.(1999) claimed thatthe N400 (now peaking between 270 and 300 msec). Theydid not effect reflects thesemantic incompatibilitybetween the find an early negativityin theremaining twoconditions, semantic expectation thatis derived from thesentence noteven inthe semantically anomalous condition where context and themeaning of theacoustic word input. word onset was identical tothe highest-cloze probability Thisaccount assumesthat the incoming acoustic in-

968Journal ofCognitive Neuroscience Volume 13,Number 7 formation issemantically analyzed and contrasted with The issueof the exact timecourse of contextual thesemantic expectation. Thisaspect was notfurther influences on spoken-wordrecognition isimportant elaborated interms of specific lexical representations, for our understanding of theunderlying cognitive archi- or more general semantic expectations. VanPetten tecture of thelanguage system.ERP research allowsus et al.concluded thatthe N400 effect reflects seman- toinvestigate thisunderlying cognitive architecture tic processingof theperceived word and thatthis throughidentification of electrophysiological correlates semantic processingbegins on partial and incom- of spoken-wordrecognition processes.The three stud- plete informationabout theperceived word. iesmentioned above indicate thatcontext hasan early The different resultsobtained inthese studies,that is, effect on spoken-wordrecognition. The present study an early negativityversus an early onset of theN400 followson from these studiesand was designed togive a effect, resulted indifferent interpretations.The finding better insightinto this early context effect. of an early negativityled Connollyand Phillips(1994) to The timecourse of contextual influences on spoken- conclude thaton thebasis of thepreceding context a word recognition was evaluated withERPs. Taking into specific phonologicalexpectation isformed. The early account thepossibility of somedelay between under- onset oftheN400 effect inVan Petten et al.’sstudyled lyingprocesses and theirmanifestation inthe ERP wave- themto conclude thata semantic expectation isformed. form,the latest momentat whichcontext startsto exert Despitethese contrasting results,both studies provide itsinfluence was assumedto be revealed asthe onset of evidence for early contextual influences during word acongruity effect inthe waveforms, as indicated bythe recognition. However,neither aphonologicalnor a divergence between acongruent and an incongruent semantic expectation account necessarily impliesthat condition.We used semanticallyconstraining Dutch context already influences word recognition priorto sentences withsentence-final wordsthat differed across lexical access. Supposethat, following the Shortlist three conditions.In the fully congruent (FC) condition, model(Norris, 1994), contextual influences arise only sentences ended withthe highest-cloze probabilityword after thebottom– up activation of anumberof lexical for thatsentence: ’’De schilderkleurde de detailsin met candidates on thebasis of theinitial phonemes of the een klein penseel’’(’’The painter colored thedetails perceived word.If thecontextual specificationsdo not witha smallpaint brush’ ’).The other two conditions supportany of thelexical candidates inthe set (e.g., on bothended anomalously,but the point at whichthe thebasis of theirsemantic features), acongruency effect sentence-final wordsbecame incongruent differed be- occurs, showingup either asan N400 effect (Van Petten tween these twoconditions. The completionsof the et al.,1999) or asan early negativity(Connolly & Phillips, sentences inthe initially congruent (IC) conditionbegan 1994). withthe same phonemesas thehighest-cloze probability Thisaccount fitswith how Hagoort and Brown (2000) wordsin the FC completions:’ ’De schilderkleurde de interpreted theirresults of arecent ERPstudy.The detailsin met een klein pensioen’’(’’The painter colored authorspresented theirsubjects with spoken sentences thedetails with a smallpension’ ’).Incontrast, thefully thatended witha semanticallycongruent or anomalous incongruent (FI) sentence-final wordshad initial pho- word thatdid not have the same phonemiconset as the nemes thatdiffered from thehighest-cloze probability congruent completions.A biphasicnegative shiftwas word:’ ’De schilderkleurde de detailsin met een klein observedto the semantically anomalous endings. This doolhof ’’(’’The painter colored thedetails with a small biphasicshift was composedof two effects, an early labyrinth’’).We hypothesizedthat the onset of the effect thatpeaked around 250 msec (the N250 effect) congruity effect between theFC and FIconditions and theN400 effect. The authorssuggested thatthe shouldprecede theonset of thecongruity effect be- N250 effect occurs whenever ’’ . . . thecontextual speci- tween theFC and IC conditions.We were alsocurious to fications do notsupport the form-based activationof a see howthis congruity effect wouldmanifest itself;as lexical candidate . . .’’(p.1528). theonset of amonophasicN400 effect as inthe Van The fact thatthese studiesyield contrasting results Petten et al.study (1999), or asa biphasicnegative shift (early negativityvs. early onset of the N400 effect) consistingof an early negative shiftand an N400 effect as remainssomewhat surprising, and afew remarks are in inthe Connolly and Phillipsstudy (1994) and the order. The grand average waveforms of Connollyand Hagoort and Brown study(2000). Phillips(1994) are rather noisy,and identification of We alsoinvestigated ERP effects asa function of the separate componentsis therefore difficult. On theother momentat whichthe sentence-final wordsin the FC and hand,although Van Petten et al.(1999) claim notto ICconditionsstarted to acoustically diverge from each havefound an early negativity,inspection of thewave- other.This moment was labeled the divergencepoint . formsof theirExperiment 3does reveal thepossibility of We were interested inwhether themanifestation of the an early negativity,at least inthe rhymeand fully congruity effect based on word onset (FC vs.FI) would anomalousconditions. In itself, this finding wouldnot differ from thecongruity effect based on thedivergence harmtheir account, butit could add evidence tothe point(FC vs.IC). Thisline of investigationprovides an existence of aseparate early negativity. additionalperspective on thevalidity of thedistinction

van den Brink,Brown, and Hagoort 969 7 970

Fully Congruent Initially Congruent ora Journal Fully Incongruent

Amplitude [mV] F7 F3 Fz F4 F8 -6 fof -4 ontv Cognitive -2 0 2 4 Neuroscience 6 0 200 400 600 800 1000 1200 Time [msec]

FT7 FC3 FCz FC4 FT8

LT C3 Cz C4 RT

LP P3 Pz P4 RP oueVolume 3 13, ubrNumber Figure 1. Connected speech. Grand average ERPs from 20 scalp sites, to sentence-final words that were congruent (solid line), semantically anomalous but shared initial phonemes with semantically congruent completions (dotted line), and semantically anomalous and did not share initial phonemes with congruent completions (alternating dash/dot line), after normalization in the 150-msec prestimulus interval. Time 0 is the onset of sentence-final words. The time axis is in milliseconds. Note that negative polarity is plotted upwards 7 in this and subsequent figures. between an early negative shiftand theN400 effect morphologyare similarto previouslyreported N400 during spoken-wordrecognition. effects. Finally,Figure 1showsa late positivitybetween 600 and 1000 msec,which is largest inthe IC condition. Thislate positivityreaches maximalamplitude at around RESULTS 800 msec and ismaximal over parietal sites.In the The data of five subjectswere notanalyzed: The data of literature, there are indicationsthat late positivities one subject were lostbecause of acomputer malfunc- reflect wrap-upprocesses at theend of sentences (cf. tionand thedata of four othersshowed excessive Juottonen,Revonsuo, & Lang, 1996). alphaactivity (a pronounced 10-Hz rhythmthroughout Statistical analysesof thecongruity effects consisted thewaveforms). As thisstudy was designed to inves- of anumberof repeated measures analysesof variance tigate thepossible existence of arelativelysmall and (ANOVAs) withmean amplitudevalues computed for short-livedearly negativity,we were concerned that each subject and each electrode indifferent latency excessive alphawould distort the signals in this early windows:(a) 150–250 msec after critical-word onset for latency windowto such an extent thatit would influ- theearly negativity(N200), (b) 300–500 msec after ence theresults. For theremaining 21 subjects,data final-word onset for theN400, and (c) 600–1000 msec from critical trialswere analyzed according tothe after final-word onset for thelate positivity.The latency following procedure. Priorto off-line averaging, all windowswere determined after careful visualinspec- single-trialwaveforms were screened for eye move- tionof thegrand average waveforms. The latency ments,electrode drifting,amplifier blocking, and EMG windowfor theearly negativitycorresponds tothe artifacts ina critical windowthat ranged from 150 msec onset of theascending flank and theoffset of the before onset of thesentence-final word to1900 msec descending flank. The N400 latency windowcorre- after onset of thesentence-final word.Trials containing spondsto theonset of theascending flank and 100 artifacts were rejected (12.8% inFC, 13.4% inIC, and msec after itsmaximal amplitude. This 300- to500- 11.8% inFI). For each subject, average waveforms were msec intervalis a standard timewindow for measuring computed across all remaining trialsper conditionafter N400 effects. The latency windowfor thelate positivity normalizing thewaveforms of theindividual trials on corresponds to theonset of theascending flank and thebasis of theaveraged activityof 150 msec before 200 msec after itsmaximal amplitude. For each latency onset of thesentence-final word.This is a standard window,the results were firstanalyzed inan omnibus baseliningprocedure wherebythe average of the150- ANOVA thatcrossed all three levelsof thecongruity msec epoch issubtracted from each subsequenttime pointin the waveform. Figure 1displaysthe grand average waveforms by electrode sitetime-locked to the onset of thesentence- Amplitude [ mV] Fully Congruent Initially Congruent final word.There are several thingsto note. First,in all Fully Incongruent three conditions,the sentence-final wordselicited an -6 Fz N200 N400 N100 component.This component appears tobe larger (butis in fact not) inthe IC conditionthan in the FC -4 and FIconditions.This is most visible in the frontal to central electrodes. 2 Itis not common to find aclear -2 N100 component ina studyusing natural connected 0 speech,given thecontinuous nature of thespeech signal(Connolly et al.,1990, 1992, 1994). However,in 2 our study,all sentence-final wordsbegan witha plosive, whichis a relativelyclear onset marker inconnected 4 speech.In addition, the homogeneity of thesentence- final word onsetspresumably added to theclear pres- 6 ence of theN100 component inthe averaged wave- 0 200 400 600 800 1000 1200 forms.Second, anegativityat approximately200 msec Time [msec] isvisible in the waveforms. This negativity is apparent in all three conditions,but is largest intheFI conditionand ismost visible over thefrontal sites(see alsoFigure 2). Figure 2. Connected speech. Grand average ERPsfrom the Fz Third,the semantically anomalous sentence-final words electrode, to sentence-final wordsthat were congruent (solidline), inthe IC and FIconditionselicit abroad negativity semantically anomalousbut shared initialphonemes withsemantically peaking at approximately400 msec,which is more congruent completions (dotted line), and semantically anomalous and did not share initialphonemes withcongruent completions negative thanthe ERP elicited inthe FC condition.In (alternating dash/dot line), after normalizationin the 150-msec turn,this broad negativityis larger inthe FI condition prestimulus interval. Time 0isthe onset ofsentence-final words.The thanin the IC condition.Its latency characteristics and time axisis in milliseconds.

van den Brink,Brown, and Hagoort 971 factor (FC,IC,and FI)withthe 29-level electrode TheEarly Negativity/N200Latency Window: factor. Inaddition to the omnibus ANOVA, apriori 150–250 msec pairwisecomparisons between thecongruity conditions Table 1displaysthe results of themean ERP amplitude were tested usingANOVAs witha 2-level congruity ANOVAs inthe 150– 250-msec latency range. The omnibus factor. For theN200 latency window,we expected ANOVA for theN200 latency windowresulted ina signifi- theERP inthe FC condition(baseline) todiffer in cant maineffect of congruity.The aprioripairwise com- amplitudefrom theERP inthe FI condition(FC vs.FI), parisonsrevealed thatthe FI completionselicited alarger butnot from theone inthe IC condition(FC vs.IC). In N200 thanthe FC completions(corresponding toan effect theN400 latency window,as well asthe late positivity of 0.71 mV),and thatthe ERPs in the FC and ICconditions latency window,we expected theERP inthe FC con- didnot significantly differ inamplitude (a difference of ditionto differ inamplitude from theERPs in both the 0.17 mV).Inthese pairwiseanalyses, none of theinter- FI(FC vs.FI) and theIC condition(FC vs.IC), but actions of congruity withelectrodes reached significance. these latter were notexpected to differ from each Topographical analysesof theFC versusFI condition other (FI vs.IC). Scalp distributionsof thecongruity revealed nosignificant interactions of congruity withsite. effects were subsequentlyexplored inthree separate ANOVAs: an ANOVA on anterior versusposterior, with asite(anterior/ posterior)by electrode design (anterior: TheN400 Latency Window: 300–500 msec Fz, FCz, F3, F4, F7, F8, FC3, FC4, FT7, FT8; posterior: Cz, Pz,CP3, CP4, LTP, RTP, P3, P4, LP, RP); anterior left Table 2displaysthe results of themean ERP amplitude versusanterior right,with a site(left/ righthemisphere) ANOVAs inthe 300– 500-msec latency range. The omnibus byelectrode design (anterior left: AF3, F3, F7, FC3, ANOVA indicated thatthe basic congruity effect inthe FT7; anterior right:AF4, F4, F8, FC4, FT8); posterior N400 latency windowwas robust.Further analysisre- left versusposterior right, with a site(left/ righthemi- vealed thatboth the FI and theIC completionselicited sphere) byelectrode design (posteriorleft: CP3,LTP, alarger N400 thanthe FC completions(corresponding to P3,LP, PO7; posterior right: CP4, RTP, P4, RP, PO8). effects of 3.36 and 1.97 mV,respectively).In addition, the Univariate F testswith more thanone degree of free- FIand theIC conditionsdiffered significantlyfrom each domin the numerator were adjusted bymeans of the other inthe N400 latency window(corresponding toa Greenhouse–Geisser/ Box’sepsilonhat correction (Max- 1.38-mVaverage amplitudedifference), and an interaction well &Delaney, 1989). The original degrees offreedom withelectrodes was found aswell. Topographical analy- and adjusted p valueswill be reported. sesshowed that the congruity effects inrelation to the

Table 1. ANOVAon Mean ERPAmplitude inthe 150–250-msec Latency Range (N200) Source df F MSE p

Omnibus ANOVA(29 electrodes) Overall Con 2, 40 4.25 84.18 .023* Con El 56, 1120 1.98 0.59 .075 £ FC vs. FI Con 1, 20 6.90 154.67 .016* Con El 28, 560 2.15 0.71 .100 £ FC vs. IC Con 1, 20 0.43 9.09 .521 Con El 28, 560 2.30 .65 .080 £

Anterior vs.posterior (2 10electrodes) £ FC vs. FI Con Site 1, 20 0.08 0.18 .786 £

Anterior leftvs. anterior right (2 5electrodes) £ FC vs. FI Con Site 1, 20 0.05 0.05 .820 £

Posterior leftvs. posterior right (2 5electrodes) £ FC vs. FI Con Site 1, 20 0.44 0.45 .515 £ Con =congruity type; El= electrode. *p < .05.

972Journal ofCognitive Neuroscience Volume 13,Number 7 Table 2. ANOVAon Mean ERPAmplitude inthe 300–500-msec Latency Range (N400) Source df F MSE p

Omnibus ANOVA(29 electrodes) Overall Con 2, 40 47.71 1734.09 .000*** Con El 56, 1120 8.96 4.34 .000*** £ FC vs. FI Con 1, 20 66.46 3432.98 .000*** Con El 28, 560 12.00 7.85 .000*** £ FC vs. IC Con 1, 20 45.52 1185.66 .000*** Con El 28, 560 9.22 4.19 .000*** £ IC vs. FI Con 1, 20 18.62 583.62 .000*** Con El 28, 560 2.82 0.97 .047* £

Anterior vs.posterior (2 10electrodes) £ FC vs. FI Con Site 1, 20 8.34 47.94 .009** £ FC vs. IC Con Site 1, 20 7.14 27.12 .015* £ IC vs. FI Con Site 1, 20 0.95 2.95 .340 £

Anterior leftvs. anterior right (2 5electrodes) £ FC vs. FI Con Site 1, 20 0.47 0.49 .502 £ FC vs. IC Con Site 1, 20 0.52 0.46 .481 £ IC vs. FI Con Site 1, 20 3.47 1.90 .077 £

Posterior leftvs. posterior right (2 5electrodes) £ FC vs. FI Con Site 1, 20 0.16 0.28 .691 £ FC vs. IC Con Site 1, 20 0.81 1.03 .379 £ IC vs. FI Con Site 1, 20 4.51 2.38 .046* £ Con =congruity type; El=electrode. *p < .05. **p < .01. ***p < .001. baseline conditionwere significantlylarger over posterior 458.19, p <.001. The pairwisecomparisons revealed thananterior regions ofthescalp. Only in the posterior thatboth the FI and theIC completionselicited alarger left versusposterior right analysis was ahemispheric N400 thanthe FC completions(both p <.001). How- difference found between theIC and FIconditions, ever, theFC and theIC conditionsdid not significantly indicating thatthe difference inN400 amplitudeis larger differ from each other, F(1,20) < 1. over rightthan left posteriorareas. To establishwhether theunexpected difference in TheLate PositivityLatency Window: ERP amplitudebetween theFI and ICconditionsmight 600–1000 msec be due toan early differential effect inthe N200 latency window,we performed additionalanalyses in the N400 Table 3displaysthe results of themean ERP amplitude latency windowafter averaging thewaveforms inthe omnibusANOVAs inthe 600– 1000-msec latency range. 250–300-msec interval.This time interval corresponds to The omnibusANOVA on mean amplitudesresulted ina theperiod involving the offset of theN200 component. significant maineffect of congruity.Pairwise analyses Figure 3showsthe grand average waveforms after this revealed thatthe FC completionsdiffered significantly alternative normalizationprocedure. The omnibusAN- from boththe FI completionsand theIC completions. OVAindicated thatthe basic congruity effect inthe N400 The ERP amplitudein the FI conditionalso differed latency windowwas stillrobust, F(2,40) =16.70, MSE = significantlyfrom theERP amplitudein theIC condition.

van den Brink,Brown, and Hagoort 973 7 974 Fully Congruent Initially Congruent ora Journal Fully Incongruent

Amplitude [mV] F7 F3 -6 Fz F4 F8 fof -4 ontv Cognitive -2 0 2 4

Neuroscience 6 0 200 400 600 800 1000 1200 Time [msec]

FT7 FC3 FCz FC4 FT8

LT C3 Cz C4 RT

LP P3 Pz P4 RP oueVolume 3 13, ubrNumber Figure 3. Connected speech. Grand average ERPs from 20 scalp sites, to sentence-final words that were congruent (solid line), semantically anomalous but shared initial phonemes with congruent completions (dotted line), and semantically anomalous and did not share initial phonemes with congruent completions (alternating dash/dot line), after normalization in the 250- to 300-msec interval. Time 0 is the onset of sentence-final words. The time axis is in milliseconds. 7 Table 3. ANOVAon Mean ERPAmplitude inthe 600–1000-msec Latency Range Source df F MSE p

Omnibus ANOVA(29 electrodes) Overall Con 2, 40 26.45 836.35 .000*** Con El 56, 1120 26.83 17.24 .000*** £ FC vs. FI Con 1, 20 36.44 1633.24 .000*** Con El 28, 560 33.84 21.06 .000*** £ FC vs. IC Con 1, 20 7.10 218.07 .015* Con El 28, 560 32.47 28.12 .000*** £ IC vs. FI Con 1, 20 33.99 657.73 .000*** Con El 28, 560 5.80 2.55 .001** £ Con =congruity type; El=electrode. *p < .05. **p < .01. ***p < .001.

Again, because of thepossibility of amplitudeeffects in The onset latency analysesfor theFC versusFI thislatency windowas a consequence of earlier differ- comparisonon theamplitudes of thetwo waveforms ential effects inthe N200 latency window,we performed inthe three consecutive binsof 140–160, 150–170, and further analysesafter thealternative normalization pro- 160–180 msec revealed asignificant congruity effect cedure inthe 250– 300-msec interval. (p = .05, p = .02, p =.02, respectively).This indication Table 4displaysthe results of themean ERP ampli- of an early congruity effect disappeared inthefollowing tude omnibusANOVAs inthe 600– 1000-msec latency binsbut emerged again at 220 msec,at whichpoint the range after havingnormalized thewaveforms inthe250– congruity effect remained significant over theentire test 300-msec interval(Figure 3). The omnibusANOVA on region (500 msec). Inthe FC versusIC comparison,the mean amplitudesdid not result in a significant main congruity effect didnot start until 270 msec.So, at 150– effect of congruity.None of theconditions differed 180 msec after word onset,the waveforms of theFI significantlyfrom each other.However, Figure 3reveals conditionmomentarily departed from theFC condition. thatthis is possibly due to thedifference ineffects After thisshort-lived congruity effect, thewaveforms of between theanterior and posteriorelectrodes. Topo- theFI conditionsignificantly increased inamplitude graphical analysesindeed revealed thatthe effects in approximately50 msec earlier thanthe waveform of relation tothe FC condition(baseline) hada parietal theIC words(i.e., 220 vs.270 msec after word onset). distribution,and were moreover largest over theleft hemisphere:In the anterior/ posteriorand posteriorleft/ N200versus N400 posteriorright analyses, the interaction of thefactors congruity bysite reached significance bothin the FC Figure 4showsthe topography of mean amplitude versusFI comparisonand theFC versusIC comparison. effects between theFC and FIconditionsin the N200 and theN400 windowafter our standard normalization procedure (150 msec prestimulusinterval). Although Onset Latencies theN200 component ismost clearly visibleover frontal Figure 1showsthat the onset oftheeffects ismostclearly sites,the figure reveals thatthe N200 effect isequally visibleover frontal electrodes. Therefore, wedecided to distributedacross thescalp, whereas theN400 effect is analyze thisfrontal band.Onset latencies were estimated largest over centro-parietal sites.To establishwhether byfirst separately computingthe mean amplitudevalues these twocongruity effects havestatistically distinct for five frontal electrodes (Fz, F4, F3, F8, and F7) in20- scalpdistributions, we performed topographical analy- msec latency ranges (bins)that shifted in steps of 10 ses.First, for every subject, difference scores between msec from target onsetuntil 500 msec after target onset theFC and FIconditionswere computed for every (e.g., 0–20, 10–30, etc.). The valuesfor thelatency bins electrode inthe N200 latency windowand theN400 were submittedto ANOVAs thattested against thenull latency window.Second, ascaling procedure was hypothesisof zero difference between thea priorise- performed to avoidthat differential amplitudeeffects lected conditionsFC versusFI and FCversusIC. between thetwo latency windowswould be incorrectly

van den Brink,Brown, and Hagoort 975 Table 4. ANOVAon Mean ERPAmplitude inthe 600–1000-msec Latency Range after Averaging inthe 250–300-msec Interval Source df F MSE p

Omnibus ANOVA(29 electrodes) Overall Con 2, 40 1.26 55.92 .292 Con El 56, 1120 22.84 15.36 .000*** £ FC vs. FI Con 1, 20 1.73 107.26 .204 Con El 28, 560 28.49 20.91 .000*** £ FC vs. IC Con 1, 20 0.33 11.05 .569 Con El 28, 560 23.18 79.97 .000*** £ IC vs. FI Con 1, 20 1.30 49.46 .268 Con El 28, 560 1.77 0.72 .142 £

Anterior vs.posterior (2 10electrodes) £ FC vs. FI Con Site 1, 20 53.16 269.51 .000*** £ FC vs. IC Con Site 1, 20 68.67 360.33 .000*** £ IC vs. FI Con Site 1, 20 2.89 6.58 .104 £

Anterior leftvs. anterior right (2 5electrodes) £ FC vs. FI Con Site 1, 20 0.01 0.01 .938 £ FC vs. IC Con Site 1, 20 1.24 2.24 .279 £ IC vs. FI Con Site 1, 20 3.04 1.97 .097 £

Posterior leftvs. posterior right (2 5electrodes) £ FC vs. FI Con Site 1, 20 23.49 38.40 .000*** £ FC vs. IC Con Site 1, 20 12.74 26.15 .002** £ IC vs. FI Con Site 1, 20 1.39 1.17 .252 £ Con =congruity type; El= electrode. **p < .01. ***p < .001.

interpreted as distributioneffects. In thisprocedure, theanterior left/rightand theposterior left/ rightanal- theelectrode-specific difference scores were z-trans- yses,no significant interaction of windowby site was formed for each latency windowseparately (Ro¨sler, obtained (both Fs<1). The significant interaction of Heil,& Glowolla, 1993; see alsoMcCarthy &Wood, windowby site in the anterior/ posterioranalysis under- 1985). The z-transformed valueswere entered intoan scores thatthe N200 and N400 effects have different ANOVA thatcrossed the2-level latency windowfactor spatialdistributions, with the N400 effect havinga (N200 and N400) withthe 29-level electrode factor. A more posteriordistribution and theN200 effect having significant interaction of latency windowby electrodes, aflat distributionacross thescalp. F(28,560) =6.01, MSE = 2.19, p <.001, revealed that thecongruity effects found inthe two latency windows Time-Locking to theDivergence Point indeed havedifferent spatialdistributions across the scalp.This difference inscalp distributions was sub- Figure 5displaysthe grand average waveforms byelec- sequentlyexplored inthree additionaltopographical trode sitetime-locked on atrial-by-trialbasis to thetime ANOVAs (usingthe same electrode configurations as pointat whichthe sentence-final wordsin the FC and IC previouslydescribed). Inthe anterior/ posterioranaly- conditionsstarted to acoustically diverge from each sis,a significant interaction of windowby site was other.This acoustical divergence pointwas assessed obtained, F(1,20) =9.61, MSE = 20.84, p < .01. In on the basisof phonetictranscriptio nsof the sen-

976Journal ofCognitive Neuroscience Volume 13,Number 7 Figure 4. Connected speech. -6 Distribution ofthe N200 and 150_ 250 msec (N200 effect) N400 effects forfour left hemi- 300 _ 500 msec (N400 effect) sphere sites (F3,FC3, C3, P3), fourmidline sites (Fz,FCz, Cz, -5 Pz),and fourright hemisphere sites (F4,FC4, C4, P4). The N200 effect wasdetermined by -4 subtracting the mean amplitude in the 150–250-msec latency )

V -3 windowof the grand average m (

ERPforthe semantically con- d u t i gruent sentence-final words l p fromthe mean amplitudes of m -2 A the grand average ERPforthe semantically anomaloussen- tence-final wordsthat did not -1 share the same initialphonemes asthe semantically congruent words.The N400 effect 0 wasdetermined in the same manner onthe basisof the mean amplitudes in the 300- to 1 500-msec latency window. F3FC3 C3 P3 Fz FCz Cz Pz F4 FC4 C4 P4

Electrodes

tence-final words.The timeperiod preceding thisdiver- of contextual influences onspoken-wordrecognition. As gence pointcorresponds tothe mean timeperiod of hypothesized,the onset of thecongruity effect between segmental overlap between thetwo conditions,which theFC and theFI conditionspreceded thatof theFC was 220 msec.Therefore, inthe alignment inFigure 5, and theIC conditions.The waveforms of theFI con- the zero pointroughly corresponds toword onset. ditionfirst diverged momentarilyfrom theFC condition However,since informationabout theexact onset of inthe latency intervalof 140–180 msec.This short-lived each sentence-final word islost in this time-locking effect disappeared, butemerged again at 220 msec and procedure, normalization cannot take place on thebasis persistedthroughout the entire testregion. The con- of informationrelated to word onset.Therefore, the gruityeffect between theFC and ICconditionsdid not waveforms were normalized on thebasis of theaveraged startuntil 270 msec.These resultsindicate thatat least at activityof 150 msec preceding thedivergence point. 220 msec,but possibly already at 140 msec,sentential What can beseen inthis figure isthat approximately 80 context hasan influence on theauditory word recog- msec after thedivergence point,the waveform oftheIC nitionprocess. conditionshows a steep ascending flank, resultingin We were particularlyinterested inthe manifestation of whatappears to be abiphasicN400. 3 Thisbiphasic thiscongruity effect. Would itbe amonophasicN400 morphologyis most apparent at thefrontal and fronto- effect as inthe Van Petten et al.study (1999), or a central electrodes. Parietal electrodes reveal thatthe biphasicnegative shiftconsisting of an early negative N400 component inthe IC conditionis followed bya shiftand an N400 effect as inthe Connolly and Phillips late positiveshift. study(1994) and theHagoort and Brown study(2000)? These ERP profilescan belinkedto different functional interpretationsof theelicited components.The single DISCUSSION N400 effect hypothesissuggests that the monophasic Thisstudy investigated thetime course of contextual N400 effect isa reflection of an overall semantic pro- influences on spoken-wordrecognition. We used ERPs cessing,without fractionation intolexical selection and toinvestigate thepresence of markers inthe electro- integration. The alternative positionsuggests that the physiologicalsignal that reveal themoment at which early negative shiftand theN400 effect are two distinct context startsto havean effect on word recognition. We effects, reflecting different aspects of thespoken-word hypothesizedthat if context exerts an influence early on recognition process.Our grand average waveforms (Fig- inthe signal, the ERP of theFI conditionshould diverge ures 1and 2) revealed two clear negative deflections, earlier thanthe ERP of theIC condition,compared to one peaking at 200 msec and theother at 400 msec.This theFC condition.The momentat whichthe FI condition supportsthe hypothesis of aseparate effect preceding startsto diverge providesan upperestimate of theonset theN400 inthe auditory domain.

van den Brink,Brown, and Hagoort 977 7 978

Fully Congruent Initially Congruent ora Journal

Amplitude [mV] d F7 F3 -6 Fz F4 F8 fof -4 ontv Cognitive -2 0 2 4 Neuroscience 6 0 200 400 600 800 1000 1200 Time [msec]

FT7 FC3 FCz FC4 FT8

LT C3 Cz C4 RT

LP P3 Pz P4 RP oueVolume 3 13, ubrNumber

Figure 5. Connected speech. Grand average ERPs from 20 scalp sites, to sentence-final words that were congruent (solid line), or semantically anomalous but shared initial phonemes with congruent completions (dotted line), after time locking to the moment at which these words acoustically started to diverge from each other. Line d marks the divergence point of

7 the sentence-final words. The time axis is in milliseconds. The early negativityor N200 component was visiblein Finally,the topographical anterior versusposterior all three conditionswith its morphology most pro- analysisafter scaling of theabsolute size of theeffects nounced over frontal sites.Statistical analysesrevealed revealed thatthe N200 and N400 effects havesignifi- thatthe N200 inthe FI conditionwas larger thanthe cantly different spatialdistributions. Figure 4showsthat N200 inthe FC conditionand thatthe latter didnot differ theN200 effect hadan equal distributionfrom front to inamplitude from theN200 obtained inthe IC condition. back, whereas theN400 effect hada centro-parietal The finding thatan early negativitycould beobtained in distribution.Statistically significant differences inscalp all three conditionswith the amplitude differentially distributionare usuallyinterpreted as reflecting the modulated bythe experimental conditionscould be an activityof at least partlydistinct neuronal populations. indicationthat the N200 effect reflects adistinctaspect of Taken together, these four findings,(a) an early thespoken language comprehensionprocess. negativityvisible in all conditions,but larger inthe FI However,the single N400 effect hypothesiscould still condition,(b) theabsence of an early negativityeffect, be maintained on thebasis of theobtained electro- together withthe presence of an N400 effect inthe IC physiologicalprofile. One could argue thatthe N200 conditionrelative to theFC condition,(c) theearly effect isnot a separate effect, butinstead isthe first part negativitystrictly time-locked toword onset and not of abiphasicN400 effect, and thatthis biphasic N400 affected bythe divergence point,and (d) thedifferent effect reflects an undifferentiated semantic process.This scalpdistributions of theearly negative shiftand the wouldimply that the modulation brought about bythe N400 effect, provideevidence insupportof thehypoth- experimental conditionsis due toa differential onsetof esisthat the N200 effect isseparate from and precedes the biphasicN400. We report several findingsthat theN400 effect. provideevidence for theclaim that the early negative The presence of an early negativityis in line with the shiftis in fact aseparate effect. findingsof Connollyand Phillips(1994) and Hagoort The notionthat the N200 effect isa separate effect and Brown (2000). However,it does notprovide evi- was enhanced bythe dissociation with the N400 effect in dence for theaccount given byConnolly and Phillips. theIC conditionrelative tothe FC condition.The N200 Theyassumed that on thebasis of thesentence context didnot differ inamplitude; however, we didobtain a an expectation of aparticular word wouldbe formed, highlysignificant N400 effect, witha large N400 ampli- and thatthe early negativitywould be elicited whenthe tude inthe IC conditioncompared tothe FC condition. initialphonemes of theperceived word didnot match Thisfinding byitself could alsobe accounted for bythe theinitial phonemes of theexpected word.The major biphasicN400 effect hypothesis.One could argue that finding thatargues against thisaccount isthe elicitation thedifference inonset of thecongruity effects isdue to of an N200 inall of our conditions,irrespective of theN400 component settingin later, namelywhen the whether the phonemescorresponded tothe initial anomalyis firstdetected. However,if theearly negativity phonemesof thehighest cloze word.Therefore, the isan integral part of theelectrophysiological profile of N200 component cannot trulybe aPMN.Even though theN400 thatvaries in onset, then the entire biphasic we cannot rule outthe possibility that contextual in- negative deflection shouldshift in time as afunction of formation can be usedon-line to specifically predict a anomalydetection. Inother words,in the IC condition, uniquelexical item,the conclusion by Van Petten et al. where theanomaly is detected later compared tothe FI (1999) seemsmore compatiblewith our findings.They condition,the early negativityshould also occur later. concluded, on thebasis of an onset of theN400 that Thisis not the case. could precede theeliciting word’sIP,thatsemantic The alternative time-lockingprocedure thataligned processingbegins on partial and incomplete information the waveforms of the FCand ICconditionsto the about theperceived word.However, instead of an early momentat whichthese two signalsstarted toacousti- onset of the N400 effect, aseparate negative shift cally diverge (the divergence point)provides informa- preceding theN400 effect was obtained inour studyas tionabout themorphology of theonset ofthecongruity well as inthe recent studyby Hagoort and Brown effects. Figure 5revealed thatat thefrontal sites,where (2000). Itis not clear whyour findingsdiffer inthis themorphology of theN200 was mostpronounced, the respect from thoseof VanPetten et al.,especially since N400 inthe IC conditionhad a steep and uniform thetwo studiesare rather similar.An importantdiffer- ascending slope.This is in contrast tothemanifestation ence between the studiescould be thatall of our of thecongruity effect inthe FI conditionin Figure 1, sentence-final wordsbegan withplosives, whereas Van where an early negativitywas obtained inthe ascending Petten et al.used manydifferent consonants.The use of slope.The finding thatafter thealternative time-locking plosivesin our studymakes the onsets of thesentence- procedure theN400 inthe IC conditionwas notpre- final wordsmore similar.The clear N100 component in ceded bya component similarto the early negativityin our waveforms providesevidence for this.Although we theFI conditionindicates thatthe early negative shift usednatural connected speech,after averaging across reflects aprocessthat occurs at or around 200 msec after trials,the waveforms stillrevealed aclear exogenous word onset and isnot part oftheN400 effect. marker of word onset.Similarly, the chances of finding

van den Brink,Brown, and Hagoort 979 theseparate N200 effect maybecome greater if word integration isdifficult. Thisaccount issupportedby our onsetsacross trialsare fairly homogeneous.In most results:We obtained asmallN400 inthe FC condition other studies,different consonant typeshave been used, and asignificantlylarger N400 inthe two semantically whichmight have introduced alatency jitter inthe incongruent conditions.We proposethat the amplitude averaged waveforms, maskingpotential N200 effects. modulationof theearly negativitypreceding theN400 The early negativitywe obtained isreminiscent of effect reflects thelexical selection processthat occurs at another negativitythat emerges inthe 200-msec range, theinterface of lexical form and contextual meaning (cf. the mismatchnegativity (MMN). Thiscomponent is Hagoort &Brown,2000). Analogous tothe functional related tophysical mismatches in primary auditory interpretation oftheN400, theamplitude of theN200 is processing (cf. Na¨¨ata¨nen, 1990; Na¨a¨ta¨nen &Alho, indicativeof whether theinitial assessment of theform- 1997). However,besides the primary fact thatthe ma- based activated lexical candidates reveals thepresence nipulationin our experimental conditionswas semantic of thesemantic features thatare required bythe con- innature rather thanphysical, there are several other textual specifications.A smallN200 iselicited when the arguments whyour obtained N200 effect isnot an MMN. set contains semantic features thatfit the sentence First,the MMN hasa topographical distributionthat is context (as inFC and IC), alarge N200 indicates that different from theobserved N200 effect; itismaximalat theset does notcontain semantic features thatfit the frontal electrode sites,whereas theN200 effect hasa flat preceding sentence frame well (as inFI). distributionacross thescalp. Second, itshows a polarity The exact nature of thisearly assessmentprocess is inversionat thelateral electrodes, whichis absent inthe notknown. After an analysisof theinitial sounds of a N200 inour study.Third, the electrophysiological profile word,a numberof lexical candidates are activated. Upon oftheMMN isdifferent. Ithas an earlier onset and isnot activationof these words,many semantic features that as sharplypeaked asthe N200. Therefore, we propose are associated withthem become instantlyavailable to thatthe early negative shiftin our studyhas a function- thesemantic processing system.At present itis impos- alitythat is distinct from boththe MMN and theN400 sibleto distinguish between thefollowing two accounts: effect and thatreflects aprocessin word recognition Eitherthe lexical candidates are individuallyassessed thatprecedes theintegration of aselected word intothe withrespect totheir goodness-of-fit withinthe sentence sentential context. 4 frame on thebasis of theirsemantic features (a lexical- We envisage thespoken-word recognition processas drivenprocess) or initialassessment takes place on the follows(cf. Norris,1994; Zwitserlood,1989; Marslen- basisof afield ofsemantic features thatat thatmoment Wilson& Welsh,1978): On thebasis of an analysisof intimeare notlinked to specific lexical candidates inthe theinitial phoneme(s) of thespoken word anumberof set(feature-driven). The former account assumesthat lexical candidates are accessed. Thisis a purelyform- an increase oftheN200 amplitudeis seen when none of driven,bottom– up process. After activation of these thelexical candidates fit thesentential context, whereas candidates, top–down context informationstarts to ex- thelatter assumesthat a larger N200 iselicited when the ert itsinfluence. On thebasis of theirsemantic and semantic features thatare required for congruity inthe syntacticfeatures, candidates inthe set are assessedwith sentence frame are not(all) among thefield ofactivated respect to theirgoodness-of-fit withinthe sentence semantic features. frame. Inthe presence of semantic features inthe Althoughthese two functional accounts of theN200 activated set thatfit thesentence context well,further effect are speculative at thispoint, it is important to incomingacoustic informationand top–down contex- note thatthey do make different and testable predic- tual informationare used tonarrow down thenumber of tionsabout theprocessing of wordsthat vary in their candidates tothe one thatis mostcompatible with both contextual constraint insentence contexts. The results form and content constraints.This candidate issubse- of thepresent studyshow that in relatively highly quentlyintegrated inthe sentence context. If, however, constraining sentences, congruent wordselicit botha none of thelexical candidates fit thecontext well and smallN200 and averyreduced N400. Incontrast, consequently theappropriate semantic features are not incongruent wordselicit a larger N200 and an increased available, selection of theproper candidate isdifficult N400. There isevidence inthe literature thatthe N400 and can onlybe done on thebasis of theacoustic issensitive to contextual constraint.For example, tak- information.Once theincongruent word isselected ing intoaccount thatin semantically congruent senten- from theset of candidates, integration isattempted. In ces contextual constraint and cloze probabilityare thissense, semantic integration isa mandatory process: tightlylinked phenomena (cf. Kutas, Lindamood,& Integration willbe attempted for all thewords in a Hillyard,1984), thestudies by Kutas and Hillyard sentence. (1984) and VanPetten et al.(1999) reveal asensitivity Ithas been widelyassumed that the amplitude of the of theN400 tovariations of contextual constraint.In N400 indicates whether theintegration processruns these studies,when thecontextual constraint of a smoothly:A smallN400 indicates thatintegration of sentence was low,congruent words(by definition of theselected word iseasy, a large N400 indicates that lowcloze probability)elicited an N400 thatwas larger

980Journal ofCognitive Neuroscience Volume 13,Number 7 inamplitude than the N400 elicited to(high cloze) frequency of our critical wordsdid not greatly differ congruent wordsin highly constraining sentences. This across conditionsand since these wordswere pre- indicates thatalthough a word iscongruent, theab- sented insentence-final position,a lexical frequency sence of highlyconstraining context makesthe inte- effect does notseem tobe aviableaccount for the gration process to someextent more demanding. N400 effect thatwe obtained. Supposethat, in accordance withthe lexical-driven Another suggestion comes from aword primingstudy account of theN200, individuallexical candidates are byPraamstra, Meyer, and Levelt (1994). Theyexamined assessedwith respect totheir possible fit withinthe phonologicalpriming effects inan auditorylexical deci- preceding sentence. Analogous tothe N400, we would siontask and found thatthe ERP waveforms were more expect arelativelylarge N200 tooccur inresponse to negative for unrelated targets thanfor alliterating targets congruent wordsin low-constraint sentences: The ab- (e.g., beeld–mast [statue– mast] vs. beeld– beest [statue– sence of strong contextual constraintsmakes it more animal]). Also,in another experiment waveforms to difficult to assesswhether anycandidate inthe acti- unrelated targets were more negative thanto rhyming vated set fitsthe sentence frame verywell. Note that targets (e.g., graaf–steeg [duke–alley] vs.graaf– staaf thisaccount alsopredicts a larger N200 inresponse to [duke–rod]). Praamstra et al.concluded thatthe N400 congruent wordsat earlier positionsin the (high- or amplitudeis sensitiveto phonological as well asseman- low-constraint)sentence, since contextual constraint is tic manipulations.It is unclear howthese form-priming absent at thebeginning of thesentence and increases effects for wordspresented inisolation relate tothe as thesentence unfolds.However, if themodulation of processingof wordsin sentences. Note thatin thestudy theN200 amplitudereflects aprocessin which the byVan Petten et al.(1999), thephonological manipu- presence of appropriate semantic features isassessed, lationin the rhyming condition did not elicit an N400 of we wouldexpect asmallN200 tooccur, because most lower amplitudethan in the anomalous condition. semantic features are compatiblewith low constraining We proposea different viewof theapparent N400 sentences. effect, namelythat the observed shiftis carried over The functional interpretation of theN200 effect as from thepreceding N200 effect. Figure 2showsthat reflecting an initialassessment process (irrespective of theonset of theN400 inthe FI and ICconditions thefeature- or lexical-driven account) alsomakes some occurs at about 275 msec.As aresultof theN200 predictionsabout wordsdiffering incloze probabilityin effect, at 275 msec theFI conditionis already larger in equallyconstraining sentences. The present studyre- amplitudethan in the IC condition.This differential vealed thathigh-cloze probabilitywords elicit an N200 N200 effect between the twoconditions might then thatis smallin amplitude.From our claim,it followsthat lead toan add-on amplitudeeffect inthe N400 latency wordsof alower cloze probabilityshould elicit larger window.We performed additionalanalyses in this N200s, since thelexical candidates or thefield ofseman- latency windowafter normalizing thewaveforms in tic features intheactivated set wouldnot be considered the250- to 300-msec latency intervalto remove the tofit thesentence context verywell. Words withlow differential N200 effect between theFI and ICcondi- cloze probabilities(in low-constraint sentences) should tions,to see whatthe effect wouldbe on thewave- produce thelargest N200, possiblyvery close tothe formsin the N400 latency window.Figure 3showsthat N200 elicited byfully anomalous words in high-con- after normalization inthe 250- to300-msec interval,the straintsentences. These predictionsneed tobe eval- relative amplitudesof thetwo conditionsactually did uated infuture research. notdiffer from each other,and thestatistical analyses An issuethat we havenot yet touched uponbut revealed thatan N400 effect was infact absent. needs someclarification isthe apparent differential Figure 3alsoshows that after thealternative normal- N400 effect between theFI and IC conditions.It is ization procedure inthe 250- to300-msec interval,the notimmediately clear whytwo sentence-final words difference inthe size of thelate positivityeffect thatwe thatare bothanomalous in a sentence frame should observed between theFI and ICconditionsdisappears. elicitN400s thatdiffer inamplitude. One possibilityis Thiswas confirmed byour statisticalanalyses. Late thatthe N400 effect isdue toa lexical frequency effect, positivityeffects to sentence-final wordsare thoughtto since themean frequency of thewords used inthe two be related topostlexical wrap-upprocesses (cf. Juotto- conditionsdiffered, albeit onlyslightly (a log frequency nen et al.,1996). Presumably,after thesentence-final of 2.62 per 42 millionin IC and 2.49 per 42 millionin word hasbeen integrated inthe context, an evaluation FI). However,the work by Van Petten and Kutas (1990, of theoverall message takes place. The late positivity, see alsoVan Petten, 1995) hasshown that frequency whichis largest inthe FI and ICconditions,indicates effects dissipate over the courseofasentence. thatoverall evaluation of thesentence isdifficult, since Althoughlow frequency wordsare usuallyassociated sentence-final wordsin these conditionswere anoma- withlarger N400s thanhigh frequency words,this lous. frequency effect disappearswhen contextual constraint Overall, theresults obtained inthis experiment sug- isincreased asthe sentence unfolds.Since themean gest thatthe N200 effect reflects aprocessthat occurs at

van den Brink,Brown, and Hagoort 981 theinterface of lexical form and contextual meaning, in The 261 tripletswere derived from alarger set of whichform-based-activated lexical candidates are as- sentence materials thathad been submittedto a cloze sessedwith respect to theirsemantic goodness-of-fit test.Thirty subjects from thesubject poolof theMax withthe sentential contextual specifications.After this PlanckInstitute for Psycholinguisticswere given alistof early assessmentprocess, selection of one specific can- 350 sentences withthe final word omitted.Subjects didate takes place on thebasis of additionalacoustic were asked tocarefully read thesentences and tofill inputand supportingcontext. The N400 effect reflects inthefirst word thatcame tomind at theposition of the semantic integration of theselected candidate intothe omittedsentence-final word.On thebasis of theresults, higher-order meaning of sentence context. Even though aset of 261 sentences witha cloze probabilityof .50 or itremainspossible that context already hasan influence higherformed thebasis for the261 tripletsused inthis before anybottom– up information has been received, experiment. Itemsfor theIC conditionwere constructed our findingsseem mostcompatible with word identifi- byreplacing thesentence-final word bya word thatdid cation modelsthat claim that there isbottom– up prior- notfit thesemantic constraintsof thepreceding context, ityof acoustic processingof theinitial signal of the butbegan withthe same phonemes(mean length of perceived word before top–down informationexerts overlap was 2.6 phonemes,range 2–4, alwaysincluding a itsinfluence. full vowel) and hadthe same lexical stressand number ofsyllablesas the high-cloze probabilityword, which was used inthe FC condition.The itemsfor theFI condition METHODS were constructed byreplacing thesentence-final word Subjects witha semanticallyanomalous word withword-initial phonemesthat differed from thebeginning phonemes The experiment was conducted with21 nativespeakers ofthehigh-cloze probabilityword and other congruent of Dutch(18 female, mean age 22, range 19–26 years) words. from thesubject poolof theMax PlanckInstitute for Because thesentences withineach tripletwere iden- Psycholinguistics.All hadnormal to corrected-to-nor- tical upto the final word,they had the same length malvision and were right-handed(three subjectsre- (mean length of 10.8 words;range 5–15) and were ported havinga left-handed parent or sibling).None of equallyconstraining; the critical wordsin the FC con- thesubjects had any neurological impairmentor had ditionhad a mean cloze probabilityof .84 (range: .50– experienced anyneurological trauma. Nor hadany of 1.0). All sentence-final wordswere reasonably well- the subjectsparticipated inthe pretest (see below). knownnouns selected from aDutch word corpus The data of five additionalsubjects were notanalyzed (CELEX, 1990); all critical wordshad a frequency of at (see Resultssection). Subjects were paidfor their least 30 countsper 42 millionor 1.48 log,with a mean participation. duration of 516 msec and amean log frequency of2.87 inthe FCcondition,538 msec and 2.62 inthe IC condition,and 515 msec and 2.49 inthe FI condition. Materials Each sentence-final word began witha plosive.This The experimental itemsconsisted of aset of 261 provideda clear physicalmarker thatfacilitated the tripletsof semanticallyconstraining sentences across alignment of theERP waveform tothe onset of the three experimental conditions.The sentences ineach sentence-final word. tripletwere identical upto the final word.In the FC Three listswere constructed toensure thatno subject condition,sentences ended witha high-cloze proba- heard thesame sentence or target word more than bilityword, e.g., ’’De schilderkleurde de detailsin once. Inaddition to the set of 261 experimental items met een klein penseel’’(’’The painter colored the (87 per conditionper list),a set of 87 fillers was detailswith a smallpaint brush’ ’).Inthe IC condition, constructed. These fillerswere all semanticallycongru- sentences ended witha semanticallyanomalous word ous,to balance thenumber of sentences thatended thathad the same initialphonemes (and lexical stress) anomalouslyand congruously.Finally, the experimental asthe highest-cloze probabilityword, e.g., ’’De schild- listswere preceded bya practice listof 20 items,which er kleurde de detailsin met een klein pensioen’’ reflected theexperimental materials.The practice list (’’The painter colored thedetails with a smallpen- was used tofamiliarize thesubjects with the experimen- sion’’).The thirdcondition served as acontrol con- tal situation. ditionwhere sentences ended witha word thatwas The experimental sentences, fillers,and practice sen- semanticallyanomalous and alsohad initial phonemes tences were all spokenby afemale speaker, withnormal thatwere totallyunexpected given the sentential intonationat anormal speakingrate, and were recorded context, e.g.,’ ’De schilderkleurde de detailsin met inone recording session.The sentences were recorded een klein doolhof ’’(’’The painter colored thedetails intriplets, making sure intonationand speakingrate witha smalllabyrinth’ ’).Thiscondition is called theFI were keptconstant withineach triplet.No specific voice condition. changes marked thesentence-final anomalies as odd in

982Journal ofCognitive Neuroscience Volume 13,Number 7 theIC and FIconditions.Sentences were spokenin a sound-attenuating boothand recorded on adigital audiotape. The DAT recordings were sampledat 16- kHzmono and stored on computer disk.A speech waveform editing systemwas used tomark the onset AF3 AF4 F7 F8 of thesentence-final words.Also, the moment at which F3 F4 Fz thesentence-final wordsin the FC and ICconditions started toacoustically diverge from each other was FT7 FT8 FC3 FCz FC4 marked asthe divergence pointfor each word individ- ually.This acoustic divergence pointwas assessedon the basisof phonetictranscriptions of thesentence-final LT C3 Cz C4 RT words. CP3 CP4

LTP RTP

Procedure Pz P3 P4 Subjects were tested individuallyin a dimlyilluminated LP RP sound-attenuating booth.They were seated ina com- PO7 PO8 fortable reclining chair,instructed tomove as littleas possible,and toldthat they would hear anumberof Oz sentences. Their taskwas to attentivelylisten to these sentences and to tryto understand them.In addition, theywere toldthat several sentences wouldbe seman- Figure 6. Distribution ofthe 29 electrodes acrossthe scalp. ticallyanomalous. No additionaltask demands were imposed. Each trialbegan witha 300-msec warning tone, placed laterally toCz, at 33% of theinteraur al followed by1200 msec of silence, thena spoken distance, (b) atemporo-parietal pair(LTP and RTP) sentence. The next trialbegan 4100 msec after the placed 30% of theinteraural distance lateral and 13% sentence offset. To ensure thatsubjects would not of thenasion– inion distance posteriorto Cz, and (c) blinkduring and shortlyafter presentationof the aparietal pairmidway between LTP/RTP and PO7/PO8 sentence, 1000 msec priorto thebeginning of the (LP and RP).Vertical eye movementswere monitored sentence, afixation point(an asterisk)was displayed viaa supra-to suborbital bipolar montage. Arightto on thecomputer screen. The asteriskremained on the left canthal bipolarmontage was used tomonitor for screen until1600 msec after offset of thespoken horizontaleye movements.Activity over theright sentence. Subjects were instructed to fixate on the mastoidbone was recorded on an additionalchannel asteriskduring presentation of thesentences, butwere todetermine if there were differential contributions free toblink and movetheir eyes whenthe asterisk was of theexperimen tal variablesto the presumabl y notdisplayed on thescreen. Subjects listenedto the neutral mastoidsite. No suchdifferential effects were stimulivia closed-ear headphones.After thepractice observed. session,the trials were presented infive blocksof The EEGand EOG recordings were amplifiedwith a approximately10 min. SynAmpModel 5083 EEGamplifier(NeuroScan, Hern- don,VA, USA), usinga hi-cutof 30 Hz(notch filter 60 Hz) and atimeconstant of 8sec (0.02 Hz).Electrode EEG Recording impedances were keptbelow 3k for theEEG record- The EEGwas recorded from 29 Ag/AgCl-sintered ing and below 5k for theEOG recording. The EEG and electrodes mountedin an elastic cap, each referred EOGsignalswere digitized on-linewith a sampling tothe left mastoid(see Figure 6for theelectrode frequency of 200 Hz. distribution).Five electrodes were placed according tothe 10% standard systemof theAmerican Electro- Acknowledgments encephalographic Society over midlinesites at Fz, FCz, Cz, Pz,and Oz locations,along withnine lateral We thank Jos van Berkum and Michael Coles fortheir support, pairsof electrodes over standard siteson frontal Valesca Kooijman and Jelle van Dijkfor their help inacquiring the ERPdata, Marlies Wassenaar forrecording the sentences, (AF3, AF4, F3, F4, F7, and F8), fronto-central (FC3 Rene´ de Bruin,John Nagengast, and Johan Weustink for and FC4), fronto-temporal (FT7 and FT8), central (C3 technical assistance, and three anonymous reviewers for and C4), centro-parietal (CP3 and CP4), parietal (P3 comments on an earlierversion ofthe manuscript. and P4),and occipital (PO7 and PO8) positions. Reprintrequests should besent to Danie¨lle van den Brink,Max Three additionalpairs were placed laterally over sym- PlanckInstitute forPsycholinguistics, P.O.Box 310, NL-6500 metrical positions:(a) atemporal pair(LT and RT) AHNijmegen, TheNetherlands, orvia e-mail:[email protected].

van den Brink,Brown, and Hagoort 983 Notes speech: Semantic ERPeffects. Neuropsychologia,38, 1518– 1530. 1. Cloze probabilityof a wordis defined as the percentage of Holcomb,P. J.(1993). Semantic primingand stimulus degra- subjects whouse that wordto end aparticularsentence (see dation: Implications forthe role ofthe N400 inlanguage Bloom &Fischler,1980). processing. Psychophysiology,30, 47–61. 2. We do not expect adifferentialN100 effect to occur Juottonen, K.,Revonsuo, A.,&Lang, H.(1996). Dissimilarage (sentences and task demands were identical inallconditions), influences on two ERPwaveforms (LPCand N400) reflecting and infact thisamplitude difference did not reach significance semantic context effect. CognitiveBrain Research,4, 99– (p =.103). Nevertheless, we were concerned that the IC 107. condition inlater latency windows might stillbe affected by Kutas, M.,& Federmeier, K.D.(2000). Electrophysiology thisearly difference. Toassess the possible effect ofthe reveals semantic memory use inlanguage comprehension. nonsignificant N100 amplitude difference, we normalized with Trends inCognitive Sciences, 12, 463–470. alatency window surrounding the N100, and performed full Kutas, M.,&Hillyard,S. A.(1980). Reading senseless statistical analyses based on thisalternative normalization sentences: Brainpotentials reflect semantic incongruity. procedure. Apartfrom a fewdetails inthe onset analyses (IC Science,207, 203–205. now diverged at 370 msec fromFC), the results on the basis of Kutas, M.,& Hillyard,S. A.(1984). Brainpotentials during thisalternative normalization procedure were the same as the reading reflect wordexpectancy and semantic association. results based on the prestimulus baseline. Nature, 307, 161–163. 3. Investigation ofthis biphasic N400 revealed that the Kutas, M.,Lindamood, T.,&Hillyard,S. A.(1984). Word second peak isrelated to wordoffset. When we time-locked expectancy and event-related brainpotentials during sen- the waveforms to wordoffset, we discovered alarge negative tence processing. In S.Kornblum &J.Requin (Eds.), peak at wordoffset, followed by asmaller positive peak inthe Preparatory states and processes (pp.217– 238). Hillsdale, signal. Thisprofile was apparent inall three conditions. This NJ:Erlbaum. leads us to posit that weare not looking at abiphasicN400, but Kutas, M.,& Van Petten, C.(1988). Event-related brainpoten- rathera monophasic N400 followed by an offset potential on tialstudies oflanguage. In P.K.Ackles, J.R.Jennings, &M. the descending flankof the N400. G.H.Coles (Eds.), Advancesin psychophysiology , vol. 3 4. We do not claimthat the N200 effect islanguage-specific (pp.139– 187). Greenwich, CT:JAI Press. (cf.Pritchard, Shappell, &Brandt, 1991), but ratherthat inthe Kutas, M.,&Van Petten, C.(1994). Psycholinguistics electrified: context ofspoken-word processing, the modulation ofthe Event-related brainpotential investigations. In M.Gernsba- N200 component can be related to adistinct aspect of cher (Ed.), Handbook ofpsycholinguistics (pp.83– 143). language processing. New York:Academic Press. Marslen-Wilson, W.D.(1987). Functional parallelismin spoken wordrecognition. In U.H.Frauenfelder &L.K.Tyler(Eds.), REFERENCES Spoken word recognition (pp.71– 102). Cambridge: MIT Press. Bloom, P.A.,&Fischler,I. (1980). Completion norms for329 Marslen-Wilson, W.D.,&Tyler,L. K.(1980). Thetemporal sentence contexts. Memory and Cognition, 8, 631–642. structure ofspoken language understanding. Cognition, 8, Brown,C. M.,&Hagoort, P.(1993). Theprocessing nature of 1–71. the N400: Evidence frommasked priming. Journal of Marslen-Wilson, W.D.,&Welsh,A. (1978). Processing inter- CognitiveNeuroscience, 5, 34–44. actions during wordrecognition incontinuous speech. 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