kC

hmosc

d on

Theresponsupprous PEadigmdivisiowith nStroopstructpolarlateracontraHowevor left(ACC)recentcallyseemswhichMatcharounquiredwhichmanag

Coga specprocestask (Sence task. A color word such as GREEN appears in anink color such as red. If the subjects task is to read theword aevidenstandanametherecolor pthe cothe wo

e (fir

cticdor19hirshteet19

era1;icip194 (vahyirpeterc a

preen at tutcutin

usl

utbe made despite lesions in the ACC, but these decisionscan not be successfully translated in manual output by

NeuroImage 13, 2936 (2001)doi:10.1006/nimg.2000.0665, available online at http://www.idealibrary.com onnd ignore the color (i.e., say green), there is noce of difficulty relative to reading the word inrd black ink. However, if the subjects task is to

the ink color and ignore the word (i.e., say red),is considerable difficulty relative to naming aatch. Reading the word interferes with naming

lor, but the color does not interfere with readingrd. This is the phenomenon of Stroop interfer-

the missing ACC (Turken and Swick, 1999). In partic-ular, the caudal regions of the ACC below the supple-mentary motor area, might be specialized in the controlof manual responses (Picard and Strick, 1996, 1997).Picard and Strick (1997) differentiate at least two cin-gulate motor areasone in the posterior portion of therostral cingulate zone (RCZ) and another in the caudalcingulate zone (CCZ). The larger RCZ is activated inColor-Word Matching Stroop Tasand Response

Stefan Zysset, Karsten Muller, Gabriele LoMax-Planck-Institute of Cognitive Neur

Received December 28, 1999; publishe

Stroop interference task requires a person tod to a specific dimension of a stimulus while

essing a competing stimulus dimension. Previ-T and fMRI studies using the Color Stroop par-have shown increased activity in the cognitiven of the cingulate cortex. In our fMRI studyine subjects, we used a ColorWord Matching

task. A frontoparietal network, includingures in the lateral prefrontal cortex, the fronto-region, the intraparietal sulcus, as well as thel occipitotemporal gyrus, was activated whensting the incongruent vs the neutral condition.er, no substantial activation in either the righthemisphere of the anterior cingulate cortex

was detected. In accordance with a series ofarticles, we argue that the ACC is not specifi-

involved in interference processes. The ACCrather involved in motor preparation processeswere controlled in the present ColorWord

ing Stroop task. We argue that the regiond the banks of the inferior frontal sulcus is re-

to solve interference problems, a conceptcan also be seen as a component of task setement. 2001 Academic Press

INTRODUCTION

nitive interference occurs when the processing ofific stimulus feature impedes the simultaneoussing of a second stimulus attribute. The Strooptroop, 1935) has become a prototypical interfer-

encrequ

A(ACColal.,bys(Bucruiloral.,gen199antal.,199actitherequcomCartegiACCdeg

Athatribexemak(Pafromoutp29: Separating Interferenceonflictann, and D. Yves von Cramon

ience, Leipzig, Germany

line November 3, 2000

or a review see MacLeod, 1991). The Stroop taskes the inhibition of competing responses.vation in the cognitive subdivision of the ACC, caudal areas 249/329), has been observed inWord Stroop tasks (Pardo et al., 1990; Bench et93; George et al., 1994; Carter et al., 1995; Der-e et al., 1998) and in the Counting Stroop tasket al., 1998). The ACC is also known to be re-

d during other cognitive interference tasks (Tay-al., 1994), in divided attention task (Corbetta et91; Bush et al., 1995), in response selection/tion tasks (Petersen et al., 1988; Frith et al.,Paus et al., 1993; Kawashima et al., 1996), ination of cognitively demanding tasks (Murtha et

96), and in error detection tasks (Dehaene et al.,for a review see Paus et al., 1998)). This cross-tion of ACcd by different tasks lends support topothesized involvement of the ACC in tasks thate subjects to resolve processing conflicts betweenting information streams. In recent articles,et al. (2000, 1999) differentiated between stra-

nd evaluative functions, demonstrating that theerforms an evaluative function reflected in theof response conflict.lternative view put forward in recent articles is

he ACC is primarily involved in functions con-ing to the process of selecting, preparing, anding motor responses determined by decision-g processes mediated by lateral prefrontal cortexet al., 1993, 1998). Command signals originatingateral prefrontal cortex are funneled to the motor

system through the ACC. Correct decisions can1053-8119/01 $35.00Copyright 2001 by Academic Press

All rights of reproduction in any form reserved.

relation to complex tasks and the smaller CCZ is acti-vated during simpler tasks and might specialize in thecontrol of motor outputs (Turken and Swick, 1999).RCZ icortexmovemany asthe prnarrowlosum32, whACC.cingulther, tinto ththe AC

In tstimulbeingmatchthe irraratiomodaltwo prfere at

In owhichley (19sion, iis septionalconstacolor nponendimenGREEink), awith tcolor othe seword (presenferencthe twprocesand ethe twtask ctraditimatchStroopvatedditiononce intaken,

Furso far

ies; only the study of Bush et al. (1998) used the fMRItechnique. The main purpose of the present study wasto validate the involvement of the anterior cingulate

execie astuverd f

jec

erigscede neue wt.

cho

nrfe19keubersideersomdled ttopowD,k.co

c

,ngror nerpLeald.e

he., hees

30 ZYSSET ET AL.s activated in conjunction with the prefrontal, occurring for tasks involving eye, face, or arments. In contrast, there does not appear to be

sociation between the activation in the CCZ andefrontal cortex. Further, the ACC is a rather

structure, extending only from the Corpus cal-to the fundus of the cingulate sulcus (CS). BAich is located dorsally to the CS, is not part of the

In most subjects, BA 32 is located in between theate and the parcingulate sulcus (if existent). Fur-he superior frontal gyrus, which extends deepe medial wall of the human cortex, is not part ofC as well.

he traditional Stroop task, one dimension of theus has to be named while the other dimension issuppressed. Subjects generate a response toone dimension of a stimulus while suppressingelevant dimension. In doing this, response prep-n and interference processes are within the sameity (verbal) and one can not exclude that theseocesses confound each other. The stimuli inter-the response preparation level.

ur study, we used a variation of the Stroop task,is based on a version from Treisman and Fearn-69). In this ColorWord Matching Stroop ver-

nterference takes place at a conceptual level andarated from the response preparation. An addi-matching process was added and subjects gave ant response (button press), which was neither aor a word. The modality of the behavioural com-

t of the task is independent of the interferingsions. Subjects were presented two words (e.g.,N written in blue ink; BLUE written in blacknd they had to match the color of the first wordhe meaning of the second word (e.g., Does thef the first word correspond with the meaning ofcond word?). Varying the dimension of the firstneutral, congruent, or incongruent words to theted color) allows for the investigation of inter-e effects. The conceptual interference betweeno dimensions of a stimulus within a matchings was separated from the response preparationxecution process. The main difference betweeno tasks is that subjects in the Matching Stroopompare two attributes of a stimuli while in theonal Stroop task they generate a response toone attribute of a stimulus. For the Matchingtask, the ACC should not be substantially acti-

when comparing neutral with interference con-s, as the manual response preparation processes,

terference is reduced and the decision has beenare the same in both conditions.

thermore, most of the imaging studies reportedwere positron emission tomography (PET) stud-

cortespencthelususe

Sub

W(alltherectwerof nnonmen

Psy

Ainteley,bloc

SlettdeclettbottmidusetheyellREblactheLOWenttionincoto pcololowwasMacvisuwornamof t(e.gof tcorrin the Stroop interference with an fMRI study,ally in the context of the separation of interfer-nd response preparation. The second purpose ofdy was to validate a different individual stimu-sion of the ColorWord Stroop task which can be

or fMRI studies.

METHOD

ts

obtained written consent from all nine subjectsht handed, 2134 years of age, 4 female) prior toanning session. All subjects had normal or cor--to-normal vision and normal color vision andative German speakers. No subject had a historyrological, major medical, or psychiatric disorder;ere taking medication at the time of measure-

physical Procedures

adapted single trial version of the ColorWordrence task (adapted from Treisman and Fearn-69) was used. The task was presented using ad design.jects were told that they would see two rows of

appear on the screen and were instructed to, via button-press, if the color of the top rowcorresponded to the color name written at therow (see Fig. 1). The index (YES-response) andfinger (NO-response) of the right hand were

o respond. During neutral trials, the letters inrow were XXXX printed in red, green, blue, or

, and the bottom row consisted of the color words GREEN, BLUE, and YELLOW printed inFor congruent trials, the top row consisted of

lor words RED, GREEN, BLUE, and YEL-printed in the congruent color. The incongru-

ondition was identical to the congruent condi-except that the color word was printed in aruent color (e.g., green printed in red), in orderduce an interference between color word andame. To prevent subjects from focusing on the

word and bluring out the top word, the top wordresented 100 ms before the lower word (see alsood, 1991; Glaser and Glaser, 1982). By this,attention is shifted automatically to the top

The subjects decided in all conditions if the colorof the top row corresponded with the color wordbottom row. The meaning of the letters or wordsXXXX or GREEN) was task irrelevant. In halftrials in all conditions the color in the top row

ponded to the color name of the bottom row.

HitsprevenThe nprodutrials,screengiven

As iand encondittral bincongno resthe nethe stfilledinterveach (neach ttype d

MRI S

The(Medsslices2-mmeringshot, g

30 ms, 40 flip angle). Two functional runs with 210time points each were run, with each time point sam-pling over the 16 slices. Prior to the functional runs,

16e a

I

he0 ws sstrIures. A/1alta

o aicionfor

w-Te

s 3dum

s wcealtrrefu

t tsteionsteionheareall4;ahistrag

darel

ignauel

t is. Tulae t

FIG.the threof the Cword cothree ethree experiod a

31THE MATCHING STROOPand foils were presented in random order tot subjects from developing response tendencies.

umber of presented words (1 to 4) per trial wereced in random order. One block consisted of 20each lasting 1.5 s. The words remained on theuntil the next trial started, independent of the

response.llustrated in Fig. 1, each functional run startedded with 30 s of fixation on a small dot (baseline

ion). For the ColorWord Stroop task, four neu-locks alternated with four congruent and fourruent blocks. Each stimuli was presented and, ifponse was given after a maximal time of 1.5 s,xt trial was presented. If a response was given,imulus disappeared and the residual time wasby a blank screen. Given a fixed interstimulusal of 1.5 s, subjects completed 20 trials duringeutral/congruent/incongruent) block, 80 trials of

ype during a single run, and 160 trials of eachuring the two runs.

canning Procedure

experiment was carried out on a 3T scannerpec 30/100, Bruker, Ettlingen). Sixteen axial(19.2 cm FOV, 64 by 64 matrix, 5-mm thickness,spacing), parallel to the ACPC plane and cov-the whole brain were acquired using a singleradient recalled EPI sequence (TR 2000 ms, TE

thewer

fMR

T200ThiregifMR

Dcorrrunof 1signwas

TtacttratpertersEPIthesThijectvolunesspationi.e.,Thethethatheizatingizat

Tsquseri199ZarstataveThe(squmoddesa Gmodthadomcalcwer

1. Trial examples and design. Examples of single trials fore conditions, neutral (N), congruent (C), and incongruent (I),olor-Word Matching Stroop task. Does the color of the upperrrespond with the meaning of the lower word? For the upperxamples, the correct answer would be NO, for the loweramples the correct answer would be YES. (B) The baselinet the beginning and end of each functional run.anatomical MDEFT-slices and 16 EPI-T1 slicescquired.

Data Analysis

fMRI data were processed on an SGI Originith in-house software (Lohmann et al., 2000).

oftware package contains tools for preprocessing,ation, statistical evaluation, and presentation of

data.ing reconstruction of the functional data, the twoponding runs were concatenated into a singletemporal highpass filter with a cutoff frequency

20 Hz was used for baseline correction of the. The increased autocorrelation due to filteringken into account during statistical evaluation.lign the functional dataslices onto a 3-D stereo-coordinate reference system, a rigid linear regis-

with 6 df (3 rotational, 3 translational) wasmed. The rotational and translational parame-ere acquired on the basis of the MDEFT and1 slices to achieve an optimal match betweenslices and the individual 3-D reference data set.-D reference data set was acquired for each sub-ring a previous scanning session. The MDEFT

e data set with 160 slices and 1 mm slice thick-as standardized to the Talairach stereotactic

(Talairach and Tournoux, 1988). The same rota-and translational parameters were normalized,ansformed by linear scaling to a standard size.sulting parameters were then used to transformnctional slices using trilinear interpolation, sohe resulting functional slices were aligned withreotactic coordinate system. This linear normal-process was improved by a subsequent process-

p that performs an additional nonlinear normal-(Thirion, 1998).statistical evaluation was based on a least-s estimation using the general linear model fory autocorrelated observations (see also Friston,Worsley and Friston, 1995; Aguirre et al., 1997;n et al., 1997)). First, for each individual subject,ical parametric maps were generated and wereed over all subjects afterwards (Bosch, 2000).esign matrix was generated with a boxcare wave) function and a response delay of 6 s. Theequation, including the observation data, thematrix and the error term, was convolved with

ssian kernel of dispersion of 4 s FWHM. Theincludes an estimate of temporal autocorrelationused to estimate the effective degrees of free-

he contrast between the different conditions wasted using the t statistic. Subsequently, t valuesransformed to z scores. As the individual func-

tionaltic refperforplyingBosch

Behav

Forconditaveragthan ims) orms). TgruenaveragA repgruenacrossmain eepochcondit0.025)fered m0.06).the inremaiperimexceptdiffereErrortionseffectCondi(F 5 0

fMRI Results

The main contrast of interest in the ColorWordchinsel(p

laraledimo sFors.oncati

octh

esst

t oprlo

eretohe

onextiorlyerith

y conate).sh

vio

her i

canavt thtr

ces.te

w fpatste

FIG.SE) andtion timblock (1

32 ZYSSET ET AL.datasets were all aligned to the same stereotac-erence space a group analysis of fMRI-data wasmed by averaging individual z maps and multi-each z value with =N (N, number of subjects;

, 2000).

RESULTS

ioral Results

the Color Stroop task RTs from three differentions were analyzed. In the neutral condition,ed RTs were shorter (mean 613 ms, SE 33 ms)

n the congruent condition (mean 642 ms, SE 39the incongruent condition (mean 724 ms, SE 46

he RT difference between the neutral and incon-t condition was 111 ms. Figure 2 illustrates theed RTs over the eight periods in each condition.

eated-measures condition (interference vs con-t vs incongruent) 3 epoch (eight time epochstwo scans) ANOVA demonstrated a significantffect for condition (F 5 12.63, df 5 2, P 5 0.001),(F 5 7.79, df 5 7, P , 0.001) and significantion 3 epoch interaction (F 5 1.98, df 5 14, P 5. The neutral and congruent condition only dif-

arginally from each other (F 5 4.73, df 5 1, P 5The interference effect between the neutral andcongruent condition was reduced over time, butned significant over the entire period of the ex-ent (paired t test, df 5 8, P , 0.05) with theion of the first block of the second scan where thence was only marginally significant (P 5 0.06).rates differed only marginally between condi-

(F 5 3.16, df 5 2, P 5 0.07), but a significantwas found for epoch (F 5 2.70, df 5 7, P 5 0.018).tion and epoch did not interact with each other.83, df 5 14, P 5 0.63).

MatagationareatopolateTabvatemax

N(seeoldscanregiandtraldiss

IncorrTheparriorwassphfron

Wditicortlocaneaantand

Bditi(bilrowthrepre

Tcleanifibehthatheprocess

Inshocompoinof in

2. Mean reaction time (and standard error of measurement,error rates for the Color-Word Matching Stroop task. Reac-

es were averaged over all nine subjects for each presentationthrough 8).ing Stroop task was the incongruent conditiont the neutral condition. This interference condi-icted activation in the presupplementary motorSMA), the inferior frontal sulcus (IFS), the fron-

r cortex, the intraparietal sulcus (IPS), and thel occipitotemporal gyrus (Fusiform gyrus; FG).1 shows the Talairach coordinates of the acti-regions local maxima and the correspondingum z values.ubstantial activation in the ACC could be found

ig. 3, middle panel), even by lowering the thresh-by contrasting only within the first of the twoThe medial cortex activation was located in theof the preSMA or paracingulate gyrus (BA 8/32),nnot be attributed to the ACC proper. The ven-p of the activated region reaches into RCZ, asiated by Picard and Strick (1996).e lateral prefrontal cortex (PFC), the activation

ponded to regions along the IFS (left . right).rongest activation was located in the posterior

f the IFS, extending posteriorally along the infe-ecentral sulcus. An additional focus of activationcated in the anterior tip of the IFS (left hemi-only). Furthermore, an activation in the right

polar cortex was detected (see Fig. 3, left panel).n comparing the congruent with the neutral con-

, the posterior IFS, the IPS, and the frontopolarwere activated (see Fig. 3, middle row). The

ns of the IPS and frontopolar activations areidentical, but the left IFS activation lies more

or. The activation in preSMA, the anterior IFS,e FG disappeared.ontrasting the congruent vs the incongruent con-, activations only in the left posterior IFS, the FGral), and left cuneus remained (see Fig. 3, bottomZ values were clearly reduced and had to beolded at a z value of 4 instead of 6.5 as in theus comparisons.

DISCUSSION

ColorWord Matching Stroop task produced anterference effect (111 ms), which remained sig-t during the entire experimental session. The

ioral results seem sufficiently similar to suggeste main sources of difficulty were the same as in

aditional Stroop task. Introducing a matchings did not seem to prevent the interference pro-

restingly, the ColorWord Stroop task did notacilitation effects during the congruent conditionred to the neutral condition. As MacLeod (1991)out, facilitation is not a necessary concomitantrference and is usually much less than the cor-

responmissinspeed1982;sponsecongru

WheconditFG arings oal., 19

The S

NoACC otwo ru(1998)activaactivabe cleauted tstudieinvest(Pardo

TABLE 1

Talairach Coordinates, Maximum Z Value of the Local Maxima, and Volume of the Activated Regions for the Threes C

olx

1 20238 102

44 11238 7

31 6221 120

25 56238 42

40 30

239 1443 2

240 831 6

222 8122 63

237 15229 59

31 49214 4

Note.

33THE MATCHING STROOPding inferference. A plausible explanation of theg facilitation might be the problem of trying toup an already rapid response (Glaser and Glaser,MacLeod, 1991). It appears that the manual re-

process can not be sped up significantly by theent information.n contrasting the incongruent vs the neutralion, the posterior IFS, the IPS, preSMA, and thee activated. This corresponds well with the find-f other studies using Stroop paradigms (Bush et98; Carter et al., 2000).

troop Task and the ACC

substantial activation could be found in ther in the CS. Even by analyzing only the firstns of the experiment, as done by Bush et al., no significant activation could be found. Thetion lying closest to the ACC or CS were thetions in the pSMA. These activations appear torly located above the CS and cannot be attrib-

o the ACC. This clearly contradicts numerouss that employed the Stroop task in order toigate the functional neuroanatomy of the ACC

et al., 1990; Bench et al., 1993; George et al.,

199Derquefromin t

Tandtheuli,a reeraintetheratifounproraticessingwhithe(orconStro

Different Contrasts: Neutral vs Incongruent, Neutral v

Talairach coordinates

Z max Vy z

26 42 8.905 30 12.55

15 36 9.0035 5 7.7953 15 8.67

277 43 11.52269 44 10.78272 1 9.77273 22 9.92

25 29 8.7616 36 7.6741 5 8.3352 4 7.89

277 43 9.83272 57 9.91

5 31 7.26252 29 7.54249 210 7.34299 0 5.45

Z values were thresholded at Z . 6.5 (for congruent vs incongruen1997; Taylor et al., 1994; Carter et al., 1995;shire et al., 1998; Bush et al., 1998). Thus, theon arises, in which respect our study differshe previous studies which reported activationACC.main difference between the presently used taske traditional Stroop is that subjects performing

esent task match two attributes of different stim-ile in the traditional Stroops test they generate

onse to match one attribute of a stimulus. Gen-g the verbal response to match a stimulus isred by the second dimension of the stimulus (or

mension of a second stimulus). Response prepa-and the interference process itself are con-

d by this. With the presently used task, theseses are separated. The manual response prepa-processes are separated from the matching pro-here interference has to be reduced. The match-ocess results in a manual response process,is unaffected by the interfering dimensions of

imuli. So, by contrasting interfering vs neutralgruent) conditions, response preparation is keptnt and no ACC activation is expected. Othertasks used so far contrasted the response prep-

ongruent, and Congruent vs Incongruent

ume

Color-word stroop

Incongruent vs neutral

84 preSMA (BA 8/32)90 L. post. inferior frontal sulcus (BA 6/9/44)28 R. post. middle frontal gyrus (BA 6/9)59 L. ant. inferior frontal sulcus (BA 46/10)92 R. frontopolar cortex (BA 10)62 L. intraparietal sulcus (BA 7)79 R. intraparietal sulcus (BA 7)43 L. lateral occipitotemporal gyrus (BA 37)99 R. lateral occipitotemporal gyrus (BA 37)

Congruent vs neutral

07 L. post. inferior frontal sulcus (BA 6/9/44)07 R. post. middle frontal gyrus (BA 6/9)80 L. frontopolar cortex (BA 10)28 R. frontopolar cortex (BA 10)93 L. intraparietal sulcus (BA 7)31 R. intraparietal sulcus (BA 7)

Incongruent vs congruent

55 L. post. inferior frontal sulcus (BA 6/9/44)59 L. lateral occipitotemporal gyrus (BA 37)79 R. lateral occipitotemporal gyrus (BA 37)83 L. Cuneus (BA 18)

Z . 4) and clusters had a minimum size of 180 pixels.4,bysti

theheth

prwhsp

tinrfedionde

ceson, wpr

chst

constaop

t at

aratioence p

By tfor theSwickvolvedselectiand thsponselevel,flict. MquiresociateincreaanceThis sviousand no1999).

FIG.left late

34 ZYSSET ET AL.n process which is confounded with the interfer-rocess.his, one cannot argue that the ACC is essentialmanagement of interfering stimuli. Turken and(1999) showed that the ACC is primarily in-in response selection. In our study, the response

on component did not differ between the neutrale interference condition (both were manual re-s). Interference occurred on a more abstract

and by this reducing the effects of response con-ore traditional Stroop-interference tasks re-

to differentiate between competing responses as-d with different stimulus attributes, leading to

sed response conflicts, rather than allowing reli-on established stimulus-response associations.uggests that the ACC activation reported in pre-studies reflects the degree of response conflictt interference per se (see also Carter et al., 2000,

The

TtheFurentmaireleargsulcof tmenciesstimriesDovtaskshorior

3. Averaged Z maps of the different contrasts mapped on to a meanral cortex (x 5 240); Middle panel: the left medial surface (x 5 3);troop Task and the Inferior Frontal Sulcus

strongest activations corresponded to regions ineral PFC, extending along the banks of the IFS.

er, when contrasting only congruent vs incongru-nditions, only the activation in the left IFS re-d, which is a clear argument in favor of thence of the IFS for interference reduction. Wethat the activation in the left inferior frontalrepresents the task set management componentStroop task. In this context, task set manage-

means controlling competing response tenden-d refocusing attention on the currently relevantus dimensions. This view is supported by a se-other studies investigating task-management.

t al. (2000; see also Pollmann et al., 2000) used awitching paradigm with event-related fMRI andd that the left lateral PFC, specifically the infe-ontal sulcus, was involved in task switching. The

ain of the nine subjects examined in the study. Left column:ht panel: right lateral cortex of the brain (x 5 29).S

helatthconevaueushetanulof

e e-s

wefr

brRig

location of these activations corresponds to the locationfound in the present study. Another study by Konishi etal. (1998a), using the Wisconsin Card Sorting Test(WCSTteriorfrontaing ofthat ththe inor theconsisSchillin selealtern

Clinic

Thethe Stfrontamainlyamineogiesspeedi(1995)perforpatieningly,pronoushowe3. The3, indicessesproduties grwhenrelatelesionthe Stnamin

FunsubstrthreeStroopence efacilitatage wStroopactivanot inconflicsponsepresenalong

ference effect and task management. This point is fur-ther supported by other studies and by clinical data.

rreBOder199h,, antenh,ses, Gttodyns, Guchdnaler,tionooper,tiongnier,A.,ratoc.ett199nsiss

aenura303yshengu, AY.

enttongen, C

tionSoge,, Mgu

terf55ge,imbnace:m.

er,oop58

35THE MATCHING STROOP), found transient bilateral activation of the pos-part of the IFS. They suggest that the inferiorl areas play an essential role in the flexible shift-cognitive sets. In another study, they showede inferior frontal area was commonly involved in

hibition of different targets, as in go/no-go tasksWCST (Konishi et al., 1999, 1998b). This is

tent with the hypothesis proposed by Thompson-(1997), that the inferior frontal cortex is engagedction of available information among competingatives.

al Data and Relevance

findings of Vendrell et al. (1995) indicate thatroop taks cannot be considered globally as al test since patients with prefrontal lobe lesions

perform normally. Vendrell and co-workers ex-d patients with left lobectomies of various etiol-who performed the Stroop task accurately andly. Of the patients examined by Vendrell et al., five had left prefrontal lobectomies, all of whommed the Stroop task normally. Only one of thesets had a lesion in the cingulate cortex. Interest-patient No. 2, whose interference effect was morenced in relation to the other four patients,

d a larger left prefrontal lesion than patient No.posterior IFS appears to be intact in patient No.cating its likely role in resolving interfering pro-. Most likely, lesions in prefrontal areas do notce an all-or-nothing deficit, but cognitive abili-adually decline with increasing lesion size. Onlythe posterior division of the IFS is lesioned taskd deficits occur. Vendrell et al. concluded thats in the ACC did not produce selective changes inroop effect, but increased the reaction time forg in the noninterferent condition.

CONCLUSION

ctional MRI was used to investigate the neuralate of the Stroop interference task. There weremain findings: (1) The ColorWord Matchingtask produced reliable and pronounced interfer-ffects. This version allows the investigation oftion effects in a event-related design, an advan-hich is not available with other versions of thetask suitable for fMRI. (2) No significant ACC

tion could be found, indicating that the ACC isvolved in interference per se, but in responset. It is argued that the ACC is involved in re-selection, a process which was held low in the

tly used version of the Stroop task. (3) Regionsthe IFS appear to be involved in solving inter-

Aguiofun5:

BencR.at

Boscas

BushSustutio

BushRaizetio

Carttastr

Cartbuco

CartV.StPr

CorbS.tioem

Dehne5:

Derbfercin

DoveD.ev

FrisA

FrithacR.

GeorP.cinin9:

GeorTrgioenHu

Glasstr87REFERENCES

, G., Zarahn, E., and dEsposito, M. 1997. Empirical analysesLD fMRI statistics. II. Spatially smoothed data collectednull-hypothesis and experimental conditions. NeuroImage212.

C., Frith, C., Grasby, P., Friston, K., Paulesu, E., Frackowiak,d Dolan, R. 1993. Investigations of the functional anatomy oftion using the stroop test. Neuropsychologia 31: 907922.V. 2000. Statistical analysis of multi-subject fmri data: Thesment of focal activations. J. Magn. Reson. Imag. 11: 6164.., Rosen, B., Belliveau, J., Reppas, J., Rauch, S., Kennedy, D.,n, J., and Tootell, R. 1995. A functional magnetic resonanceof selective and divided attention during visual discrimina-

of shape, speed and color. Soc. Neurosci. Abstracts 21(2): 936.., Whalen, P., Rosen, B., Jenike, M., McInerney, S., and, S. 1998. The counting stroop: An interference task special-

for functional neuroimagingValidation study with func-MRI. Hum. Brain Mapp. 6: 270282.

C., Mintun, M., and Cohen, J. 1995. Interference and facili-effects during selective attention: An h2 15 O PET study oftask performance. Neuroimage 2: 264272.

C. S., Botvinick, M. M., and Cohen, J. D. 1999. The contri-of the anterior cingulate cortex to executive processes in

tion. Rev. Neurosci. 10: 4957.C. S., Macdonald, A. M., Botvinick, M., Ross, L. L., Stenger,Noll, D., and Cohen, J. D. 2000. Parsing executive processes:

egic vs. evaluative functions of the anterior cingulate cortex.Natl. Acad. Sci. USA 97(4): 19441948.a, M., Miezin, F., Dobmeyer, S., Shulman, G., and Petersen,1. Selective and divided attention during visual discrimina-of shape, color, and speed: Functional anatomy by positronion tomography. J. Neurosci. 11: 23832402.e, S., Posner, M., and Tucker, D. 1994. Localization of al system for error detection and compensation. Psychol. Sci.305.ire, S., Vogt, B., and Jones, A. 1998. Pain and stroop inter-

ce tasks activate separate processing modules in anteriorlate cortex. Exp. Brain Res. 118: 5260.., Pollmann, S., Schubert, T., Wiggins, C., and von Cramon,2000. Prefrontal cortex activation in task switching: An

-related fmri study. Cogn. Brain Res. 9, 103109., K. 1994. Statistical parametric maps in functional imaging:eral linear approach. Hum. Brain Mapp. 2: 189210.., Friston, K., Liddle, P., and Frackowiak, R. 1991. Willedand the prefrontal cortex in man: A study with PET. Proc.

c. London 244: 241246.M., Ketter, T., Parekh, P., Rosinky, N., Ring, H., Pazzaglia,arangell, L., Callahan, A., and Post, R. 1997. Blunted leftlate activation in mood disorder subjects during a responseerence task (the stroop). J. Neuropsychiatry Clin. Neurosci.63.M., Ketter, T., Parekh, P., Rosinsky, N., Ring, H., Casey, B.,le, M., Horwitz, B., Herscovitch, R., and Post, R. 1994. Re-

l brain activity when selecting a response despite interfer-An H215O PET study of the Stroop and an emotional Stroop.Brain Mapp. 1: 194209.M. O., and Glaser, W. R. 1982. Time course analysis of the

phenomenon. J. Exp. Psychol. Hum. Percept. Perform. 8:94.

Kawashima, R., Satoh, K., Itoh, H., Ono, S., Furumoto, S., Gotoh, R.,Koyoma, M., Yoshika, S., Takahashi, T., Takahashi, K., Yanagi-sawa, T., and Fukuda, H. 1996. Functional anatomy of GO/NO-GOdiscrimination and response selectionA PET study in man.Brain Res. 728: 7989.

Konishi, S., Nakajima, K., Uchida, I., Kameyama, M., and Mi-yashita, Y. 1999. Common inhibitory mechanism in human infe-rior prefrontal cortex revealed by event-related functional MRI.Brain 122: 981991.

Konishi, S., Nakajima, K., Uchida, I., Kameyama, M., Nakahara, K.,Sekihara, K., and Miyashita, Y. 1998a. Transient activation ofinferior prefrontal cortex during cognitive set shifting. NatureNeurosci. 1(1): 8084.

Konishi, S., Nakajima, K., Uchida, I., Sekihara, K., and Miyashita, Y.1998b. No-go dominant brain activity in human inferior prefrontalcortex revealed by functional magnetic resonance imaging. Eur.J. Neurosci. 10(3): 12091213.

Lohmann, G., Muller, K., Bosch, V., and von Cramon, D. Y. 2000.LipsiaA software package for the evaluation of functional mridata. Technical report, Max-Planck-Institute of Cognitive Neuro-science, Leipzig/Germany.

MacLeod, C. 1991. Half a century of research on the stroop effect: Anintegrative review. Psychol. Bull. 109(2): 163203.

Murtha, S., Chertkow, H., Beauregrad, M., Dixon, R., and Evans, A.1996. Anticipation causes increases blood flow to the anteriorcingulate cortex. Hum. Brain Mapp. 4: 103112.

Pardo, J., Pardo, P., Janer, K., and Raichle, M. 1990. The anteriorcingulate cortex mediates processing selection in the stroop atten-tional conflict paradigm. Proc. Natl. Acad. Sci. USA 87(1): 256259.

Paus, Tdifferflow r107 p

Paus, Thumaual, aJ. Ne

Petersen, S., Fox, P., Posner, M., Mintun, M., and Raichle, M. 1988.Positron emission tomographic studies of the cortical anatomy ofsingle word processing. Nature 331: 585589.

Picard, N., and Strick, P. 1996. Motor areas of the medial wall: Areview of their location and functional activation. Cerebral Cortex6: 342353.

Picard, N., and Strick, P. L. 1997. Activation on the medial wallduring remembered sequences of reaching movements in monkeys.J. Neurophysiol. 77(4): 21972201.

Pollmann, S., Dove, A., von Cramon, D. Y., and Wiggins, C. 2000.Event-related fmri: Comparison of conditions with varying bold-overlap. Hum. Brain Mapp. 9, 2637.

Stroop, J. 1935. Studies of interference in serial verbal reactions. J.Exp. Psychol. 18: 643662.

Talairach, P., and Tournoux, J. 1988. A Stereotactic Coplanar Atlasof the Human Brain. Thieme, Stuttgart.

Taylor, S., Kornblum, S., Minoshima, S., Oliver, L., and Koeppe, R.1994. Changes in medial cortical blood flow with a stimulus-re-sponse compatibility task. Neuropsychologia 32: 249255.

Thirion, J. P. 1998. Image matching as a diffusion process: Ananalogy with maxwells demons. Med. Image Anal. 2(3): 243260.

Thompson-Schill, S. L., DEsposito, M., Aguirre, G., and Farah, M. J.1997. Role of left inferior prefrontal cortex in retrieval of semanticknowledge: A reevaluation. Proc. Natl. Acad. Sci. USA 94: 1479214797.

Treisman, A., and Fearnley, S. 1969. The stroop test: Selective at-tention to colours and words. Nature 222: 437439.

Turken, A., and Swick, D. 1999. Response selection in the humananterior cingulate cortex. Nature Neurosci. 2(10): 920924.

Vendrell, P., Junque, C., Pujol, J., Jurado, M., Molet, J., and Graf-an,uro

sleyvisthnBOder

36 ZYSSET ET AL.., Koski, L., Caramanos, Z., and Westbury, C. 1998. Regionalence in the effects of task difficulty and motor output on bloodesponse in the human anterior cingulate cortex: A review ofet activation studies. Neuroreport 9: R37R47.., Petrides, M., Evans, A., and Meyer, E. 1993. Role of then anterior cingulate cortex in the control of oculomotor, man-nd speech responses: A positron emission tomography study.urophysiol. 70: 453469.

mNe

Worre

ZaraofunJ. 1995. The role of prefrontal regions in the stroop task.psychologia 33(3): 341352., K., and Friston, K. 1995. Analysis of fMRI time-seriesedAgain. Neuroimage 2: 359365., E., Aguirre, G., and dEsposito, M. 1997. Empirical analysesLD fMRI statistics. i. Spatially unsmoothed data collectednull-hypothesis conditions. NeuroImage 5: 179197.

INTRODUCTIONMETHODFIG. 1FIG. 2

RESULTSDISCUSSIONTABLE 1FIG. 3

CONCLUSIONREFERENCES