Cortical dynamics of visual/semantic vs. phonological analysis in picture confrontation.

Picture naming covers the main stages of word production from concept retrieval to articulation. Cortical correlates of picture naming have been characterized with both haemodynamic and neurophysiological methods but the association of specific activation patterns with the hypothesized processing stages remains elusive. Here we used categorization tasks to selectively highlight different components of picture confrontation, from visual analysis (VIS) to semantic (SEM) and phonological access (PHON), and compared these time courses of activation with that obtained during picture naming (NAM). Brain activity was recorded with whole-head magnetoencephalography (MEG). Following the initially similar activation patterns in occipital and parietal areas, task effects (stronger activation in NAM/PHON than in SEM/VIS) emerged after 300 ms, in the sustained activation of the left posterior temporal and bilateral inferior frontal cortex, apparently reflecting enhancement of phonological and phonetic/articulatory processing.