Results Results Results Conclusion - …concepts.psych.wisc.edu/posters/CNS05_HaukETAL.pdf · Results Results Results Conclusion ... RT/accuracy (typical vs. atypical), and number

Bargraphswithstandarderrorsforsignificantmain

effectsoftheERPanalysis.

Grand-meanvoltagesareplottedforelectrodesat

peaksintheERPdistributionatthecorresponding

latencies.

A)Maineffectsoftypicality.

B)Maineffectsoflexicality.

ERPtopographiesofearlymaineffects:

Mapswereinterpolatedandprojectedonatwo-

dimensionalplane.Thep-valuesbasedonpaired2-

tailedt-testsareshownontheleft,whilethe

correspondingERPamplitudesarepresentedonthe

right.F:Front;R:Right.

A)MaineffectofTypicalityat100ms.

B)MaineffectsofLexicalityat210msand240ms.

InteractionbetweenLexicality,Typicalityand

Lateralityat158ms:

A)Grand-meanvoltagesareplottedforselected

posteriorelectrodesasafunctionofelectrode,lexicality

andtypicality.

B)Statisticalparametricmaps(top)andERP

topographies(bottom)fortheTypicalitycontrast,

separatelyforwords(left)andpseudowords(right).

Sourceestimates

computedonthegrand-meanERPdisplayedfortheleft

andtherighthemisphere,respectively.Redandblue

coloursdistinguishthedirectionofeffectsaccordingto

labelswithineachfigure.

A)

B)

A)

B)

Pseudowords

Typical-Atypical

RMSforIndividualConditions

0

0.51

1.52

2.5

-100

0100

200

300

400

500

600

700

Latency(ms)

RMS(uV)

TypicalWords

AtypicalWords

TypicalPseudowords

AtypicalPseudowords

Introduction

ProcedureandMethods

Results

Results

Results

Conclusion

Cognitionand

BrainSciencesUnit

1MRCCognitionandBrainSciencesUnit,Cambridge,UK.

[Q:]WhenwouldyoupreferaSOSSAGEtoaSAUSAGE?

[A:]Atabout100ms.

ERPcorrelatesoforthographictypicalityandlexicalityinwrittenwordrecognition

HaukO1,PattersonK1,WoollamsA1,WatlingL1,PulvermüllerF1,RogersTT1,2

2DepartmentofPsychology,UniversityofWisconsin,Madison,USA

Writtenwordrecognitionreliesondifferentsources

ofinformation,whichcanberoughlyclassifiedintotwo

kinds[1,2,3]:

i)surfaceproperties(e.g.wordlengthorfrequencyof

lettercombinations)

ii)lexico-semanticproperties(e.g.wordfrequencyor

imageability).

Thisstudyaimedatdissociatingthetimecoursesand

neuralsubstratesoftheseprocesses.

Usingaspeededlexicaldecision(LD)task,event-

relatedpotentials(ERP)andminimumnorm

(MN)

sourceestimates,weinvestigatedearlyspatio-

temporalaspectsofcorticalactivationelicitedby

wordsandpseudowordsthatvariedintheir

orthographictypicality,i.e.inthefrequencyoftheir

componentletterpairs(bigrams)andtriplets

(trigrams).

TaskandStimuli

14subjectswereconfrontedoneachtrialwithaword

orapseudoword,andaskedtopressonebuttonwith

theindexfingeroftheirlefthandforwordsandwiththe

middlefingerofthesamehandforpseudowords.

Quartetsofstimuliweregeneratedsuchthatthe

surface-orthographicrelationshipbetweentypical

words(e.g.drew)andatypicalpseudowords(driew)

wasidenticaltotheonebetweenatypicalwords(view)

andtypicalpseudowords(vew)(seetablebelow).The

crucialmanipulationwasthat,inonepairofeach

matchedquartet,thewordwaslessorthographically

typical(asmeasuredbybigramandtrigram

frequencies)thanitspartner.Eachcategory

comprised50items.Thesewerematchedforlength,

frequency,RT/accuracy(typicalvs.atypical),and

numberofpseudo-homophones.

ERPanalysisandsourceestimation

63EEGand2EOGchannels(Neuroscan).Bandpass

1-20Hz.Averagereference.Baseline100ms.Artefact

threshold100uV.Onlytrialswithcorrectresponses

wereanalysed.

PeaksinRMScurveswereselected,andamplitudesat

peakelectrodessubjectedto2-by-2ANOVAs.

Furthermore,p-valuedistributionsarepresentedas

post-hoctestsandtotestforspecificityofeffects.

MNsourceestimates[4]werecomputedongrand-

meandatabeforesubtraction.OnlyvalueswithSNRs

largerthan2areshown.

TimecourseofERPdata:

A)Root-Mean-SquareandERPcurvesforindividual

conditions.Latenciesselectedforanalysisaremarked

fortheRMScurves.

B)Voltagecurvesforselectedelectrodes.

TheearliestERPeffectoftypicalitywasobservedat

~100ms(atypical>typical),andtheearliesteffectof

lexicalityat~200ms(pseudowords>words).Themain

corticalsourcesofbotheffectswerelocalisedinleft

inferiortemporalcortex.Thetwofactorsinteracted

significantlyat~150ms,withatypicalityeffectfor

wordsbutnotpseudowords.Typicalwordsactivated

perisylvianregionsbilaterally,whereasatypicalwords

elicitedstrongersourcecurrentsinleftanterior

inferiortemporalcortex:thelatterregionisthemain

siteofatrophyinpatientswithsemanticdementia,

whohaveparticulardifficultyrecognisingatypicalwords

[1].Ourdatasuggestdistinctbutinteractive

processingstagesinwrittenwordrecognition,with

theinteractionreflectingintegrationofinformationfrom

theearlierform-basedsystemandlaterlexico-semantic

processes.

-1.5-1

-0.50

0.51

1.52

2.53

100ms

284ms

Typical

Atypical

A)Typicality

ERP(µV)

-5-4-3-2-10123

210ms

240ms

512ms

552ms

Words

Pseudowords

B)Lexicality

ERP(µV)

B)LexicalityWords-Pseudowords

p>0.05

p=0.01

p>0.05

p=0.01

0.9µV

-0.9µV

0.8µV

-0.8µV

240ms

210ms

F

R

-6-4-20246

P7

P5

P3

P1

Pz

P2

P4

P6

P8

Electrode

Voltage(uV)

TypicalWords

AtypicalWords

-6-4-20246

P7

P5

P3

P1

Pz

P2

P4

P6

P8

Electrode

Voltage(uV)

TypicalPseudowords

AtypicalPseudowords

1.2µV

-1.2µV

Typical-Atypical

Typical-Atypical

p>0.05

p=0.001

p=0.01

0.9µV

-0.9µV

p>0.05

p=0.001

p=0.01

F

R

TypicalAtypical

Word

Drew

View

Pseudoword

Vew

Driew

p>0.05

p=0.01

0.7µV

-0.7µV

F

R

A)TypicalityTypical-Atypical

References

[1]Rogers,T.T.,LambonRalph,M.A.,Hodges,J.R.,Patterson,K.(2004).

Naturalselection:Theimpactofsemanticimpairmentonlexicalandobject

decision.CognitiveNeuropsychology,21,331-352.

[2]Pulvermüller,F.(2001).Brainreflectionsofwordsandtheirmeaning.Trendsin

CognitiveSciences,5(12),517-524.

[3]Hauk,O.,Pulvermüller,F.(2004).Effectsofwordlengthandfrequencyonthe

humanevent-relatedpotential.ClinicalNeurophysiology,115(5),1090-1103.

[4]Hauk,O.(2004).Keepitsimple:acaseforusingclassicalminimumnorm

estimationintheanalysisofEEGandMEGdata.Neuroimage,21(4),1612-1621.

Contact:olaf.hauk@mrc-cbu.cam.ac.ukorttrogers@wisc.edu

TypicalWords-AtypicalWords

158ms

Words-Pseudowords

210ms

Typical-Atypical

100ms

Front

Back

+0.21

-0.21

+0.12

-0.12

nA/cm2

+0.16

-0.16

nA/cm2

Back

Front

nA/cm2

TypicalWords

TypicalPseudowords

AtypicalWordsAtypicalPseudowords

Words

Typical-Atypical

100ms