A combined fMRI-MEG investigation of face information processing in the occipito-temporal cortex

[摘要] The processing of face information involves a distributed functional network of face sensitive areas in the occipitotemporal cortex and beyond. However, we do not yet have a comprehensive understanding of the temporal dynamics of these key regions and their interactions. In this study, we investigated the spatio-temporal properties of face processing in the occipitotemporal cortex using fMRI and Magnetoencephalograpy (MEG). Subjects viewed faces and objects during the experiment. Each subject's face selective regions were localized with fMRI contrasting responses to faces and objects. Their MEG data were analyzed with beamformer method, which allows for an inverse model to obtain MEG source signals. The results show that face-selective areas identified by MEG are highly consistent with that localized by fMRI. More importantly, MEG signals at the various sources reveal an intricate dynamic picture of these hierarchical face sensitive areas. Specifically, the face-selective signal at right Occipital Face Area (rOFA) reaches peak at around 110 ms, and would last longer if face components were rearranged preventing the perception of a wholistic face. Then face information engages the right posterior Fusiform Face Area (pFFA) and onto the anterior aFFA at about 120 ms and 130 ms respectively. Activity in the left fusiform gyrus peaks slightly later than the rFFA, at around 140 ms. Subsequently, a region in the inferior temporal gyrus just lateral to the rFFA is activated, with somewhat more sustained signal and peaking at about 155 ms, with a second peak at around 210 ms. The right posterior Superior Temporal Sulcus (pSTS), presumably more sensitive to dynamic facial properties, reaches peak activity at about 170 ms. Overall, while many studies have propsed the N170 as a key electrophysiological index for face processing, our source-localized MEG data suggest a significantly earlier engagement of the core ventral face-selective areas.

[学科分类] 眼科学