The cortical sources of face selective N170: A simultaneous multi-scale EEG study
Résumé
Background: 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.Objectives: In this study, we asked the following questions:– can we find an intracerebral N170 response in thelateral IOG with similar response properties as the N170 measured onthe scalp OT region in the same patient?– are the SEEG responses in the IOG and the LFG correlated with the scalp N170?Methods: 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 the OT sulcus above the right lateral FG (LFG) and 28 scalp electrodes.Results: 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 occipital surface. In addition, 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.Conclusion: Altogether, these observations provide evidence that the IOG is a major cortical generator of the face-selective scalp N170, qualifying the potential contribution of the FG and questioning a strict serial spatiotemporal organization of the human cortical face network.