1.2 Article 1
ERP MAnifestations of Processing Printed Words at Different Psycholinguistic Levels:
Time Course and Scalp Distribution
S. Bentin, Hebrew University Y. Mouchetant-Rostaing, M. H. Giard, J. F. Echallier, and J. Pernier INSERM-U280, Lyon, France.

Abstract

The aim of the present study was to examine the time course and scalp distribution of electrophysiological manifes- tations of the visual word recognition mechanism. Event-related potentials (ERPs) elicited by visually presented lists of words were recorded while subjects were involved in a series of oddball tasks. The distinction between the designated target and nontarget stimuli was manipulated to induce a different level of processing in each session (visual, phonological/pho- netic, phonological/lexical, and semantic). The ERPs of maininterest in this study were those elicited by nontarget stimuli.In the visual task the targets were twice as big as the nontar-gets. Words, pseudowords, strings of consonants, strings ofalphanumeric symbols, and strings of forms elicited a sharpnegative peak at 170 msec (N170); their distribution was lim-ited to the occipito-temporal sites. For the left hemisphereelectrode sites, the N170 was larger for orthographic than fornonorthographic stimuli and vice versa for the right hemi-sphere. The ERPs elicited by all orthographic stimuli formed aclearly distinct cluster that was different from the ERPs elicitedby nonorthographic stimuli. In the phonological/phonetic de-cision task the targets were words and pseudowords rhymingwith the French word vitrail, whereas the nontargets werewords, pseudowords, and strings of consonants that did notrhyme with vitrail. The most conspicuous potential was anegative peak at 320 msec, which was similarly elicited by pronounceable stimuli but not by nonpronounceable stimuli.The N320 was bilaterally distributed over the middle temporallobe and was significantly larger over the left than over theright hemisphere. In the phonological/lexical processing taskwe compared the ERPs elicited by strings of consonants(among which words were selected), pseudowords (amongwhich words were selected), and by words (among which pseudowords were selected). The most conspicuous potentialin these tasks was a negative potential peaking at 350 msec(N350) elicited by phonologically legal but not by phonologi-cally illegal stimuli. The distribution of the N350 was similar tothat of the N320, but it was broader and including temporo-pa-rietal areas that were not activated in the “rhyme” task. Finally,in the semantic task the targets were abstract words, and thenontargets were concrete words, pseudowords, and strings ofconsonants. The negative potential in this task peaked at 450msec. Unlike the lexical decision, the negative peak in this tasksignificantly distinguished not only between phonologically legal and illegal words but also between meaningful (words)and meaningless (pseudowords) phonologically legal struc-tures. The distribution of the N450 included the areas activatedin the lexical decision task but also areas in the fronto-centralregions. The present data corroborated the functional neuro-anatomy of word recognition systems suggested by otherneuroimaging methods and described their timecourse, sup-porting a cascade-type process that involves different but in-terconnected neural modules, each responsible for a differentlevel of processing word-related information.