The lateral inferior occipital gyrus as a major cortical source of the face-evoked N170: Evidence from simultaneous scalp and intracerebral human recordings
Résumé
The onset of a face image leads to a prominent face-selective response in human scalp electroencephalographic (EEG) recordings at occipital-temporal (OT) scalp sites: the N170. According to a widely held view, the main cortical source generating the N170 lies in the fusiform gyrus (FG), whereas the posteriorly located inferior occipital gyrus (IOG) would rather generate earlier face-selective responses. Here, we report neural responses to faces recorded in an epileptic patient using intracerebral electrodes implanted in the right IOG and above the right lateral FG (LFG). Simultaneous scalp-EEG recording identified the N170 over the right OT scalp region. The latency and amplitude of this scalp N170 were correlated at the single-trial level with the N170 recorded in the lateral IOG, close to the scalp lateral occipital surface. In addition, a positive component maximal around the latency of the N170 was prominent above the LFG, suggesting the field orientation generated in the LFG is incompatible with a strong contribution of this region to the N170 measured over lateral OT scalp. Altogether, these observations provide evidence that the IOG is a major cortical generator of the face-selective scalp N170, questioning a strict postero-anterior spatio-temporal organization of the human cortical face network.