The neural manifestation of the word concreteness effect: an electrical neuroimaging study

Previous studies have provided controversial evidence about the way in which words with different degrees of concreteness are represented in the brain. The aim of the present study was to investigate whether the processing of abstract vs. concrete words differently affected the timing and topographical distribution of ERP components. Participants were engaged in a lexical decision task (word/non-word discrimination) while EEG was recorded from 128 scalp sites. Reaction times (RTs) to words were faster than RTs to pseudowords. Words were discriminated from pseudowords since larger N2 responses to words than to pseudowords were observed over the left occipito-temporal areas at 300ms post-stimulus. Concrete words and abstract words were discriminated as early as 350ms post-stimulus, with larger responses to concrete than to abstract words over the mesial occipital regions. Concreteness-related ERP differences were also observed in the amplitudes of the later anterior LP component (between 370 and 570ms), with larger responses to abstract words than to concrete words. The LORETA source localization technique was also applied to identify the intra-cranial generators of surface potentials reflecting lexico-semantic processing. Results showed that words (both abstract and concrete) were associated with a stronger activation of the left fusiform gyrus and the left temporal cortex, as compared to pseudowords. Concrete word processing was associated with a stronger activation of the left extrastriate visual areas (namely BA 18 and BA 19) as compared to abstract word processing. By revealing the neural markers of the concreteness effect, our study contributes to the understanding of the neurogenesis of verbal semantic knowledge impairments and the incidence of these impairments in clinical populations.