The inferior occipital gyrus is a major cortical source of the face ‐evoked N170: Evidence from simultaneous scalp and intracerebral human recordings

AbstractThe sudden onset of a face image leads to a prominent face ‐selective response in human scalp electroencephalographic (EEG) recordings, peaking 170 ms after stimulus onset at occipito–temporal (OT) scalp sites: the N170 (or M170 in magnetoencephalography). According to a widely held view, the main cortical source of 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 upright and inverted faces recorded in a unique patient using multicontact intracerebral electrodes implanted in the right IOG and in th e OT sulcus above the right lateral FG (LFG). Simultaneous EEG recordings on the scalp 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 oc cipital surface. In addition, a positive component maximal around the latency of the N170 (a P170) was prominent above the internal LFG, whereas this region typically generates an N170 (or “N200”) over its external/ventral surface. This suggests that electrophysiological responses in the LFG man ifest as an equivalent dipole oriented mostly along the vertical axis with likely minimal projection to the lateral OT scalp region. Altogether, these observations provide evidence that the IOG is a major cortical generator of the...

Source: Human Brain Mapping - November 12, 2018 Category: Neurology Authors: Corentin Jacques, Jacques Jonas, Louis Maillard, Sophie Colnat ‐Coulbois, Laurent Koessler, Bruno Rossion Tags: RESEARCH ARTICLE Source Type: research