Electrophysiological comparison of grammatical processing and semantic processing of single spoken nouns.

Access to meaning from speech input is a high-speed process. However, models of word comprehension stipulate that words must be analyzed at phonological, grammatical and semantic levels. Here we used event-related potentials (ERPs) to compare on-line semantic categorization (natural/manufactured) and grammatical gender categorization (masculine/feminine) of spoken monosyllabic French noun pairs. Twenty four native French speakers were instructed to spot pairs of nouns in which both stimuli pertained to a category specified prior to each block. They could make a decision either after processing the first noun (i.e., ignore the second, Release condition), or after processing both (Hold condition). Virtually identical N4 components affecting Hold and Release ERPs in relation to category expectations were elicited by the first noun in both the tasks. Their topography was intermediary between that of the N400 and that of the Left Anterior Negativity. Despite shorter Release reaction times (RTs) for gender decisions than semantic ones, Release and Hold ERPs diverged 84 ms earlier in the semantic context than in the gender context, indicating faster onset for the processing of meaning. Conversely, the offset of Hold/Release differences was observed 42 ms earlier in the gender task than in the semantic task, suggesting an earlier completion for gender categorization. In sum, electrophysiological differences induced by semantic operations commenced earlier but recovered later than those relating to grammatical gender analysis. In convergence with previous Lateralized Readiness Potential and N200 studies, our results suggest that conscious semantic access can precede access to other types of lexical information during word comprehension in highly controlled conditions.