Electrophysiological estimates of the time course of semantic and phonological encoding during implicit picture naming

Two different event-related potential (ERP) components were used to investi gate the temporal processing of semantic and phonological encoding during i mplicit picture naming. Participants were shown pictures and carried out a dual choice go/nogo decision based on semantic information (i.e., whether t he picture was of an object or an animal) and phonological information (i.e ., whether the picture's name starts with a vowel or a consonant). In addit ion to the already established lateralized readiness potential (LRP; relate d to response preparation), we introduce the N200 (presumably related to re sponse inhibition) as a tool for measuring online language processing. Both , the LRP and the N200 data indicated that semantic processing began earlie r than phonological processing. The data are discussed in the context of la nguage production models. Therein, the LRP and N200 results, taken together , favor a serial or cascaded processing model of language production in con trast to a parallel processing account.