Abstract
We measured the fast temporal dynamics of face processing simultaneously across the human temporal cortex (TC) using intracranial recordings in eight participants. We found sites with selective responses to faces clustered in the ventral TC, which responded increasingly strongly to marine animal, bird, mammal, and human faces. Both face-selective and face-active but non-selective sites showed a posterior to anterior gradient in response time and selectivity. A sparse model focusing on information from the human face-selective sites performed as well as, or better than, anatomically distributed models when discriminating faces from non-faces stimuli. Additionally, we identified the posterior fusiform site (pFUS) as causally the most relevant node for inducing distortion of conscious face processing by direct electrical stimulation. These findings support anatomically discrete but temporally distributed response profiles in the human brain and provide a new common ground for unifying the seemingly contradictory modular and distributed modes of face processing.
Highlights
We measured the fast temporal dynamics of face processing simultaneously across the human temporal cortex (TC) using intracranial recordings in eight participants
Unlike the uniform spatial coverage of imaging methods, intracranial EEG relies on sampling from a limited number of implanted areas and leaves behind regions outside the coverage zones. While this leads to limited anatomical sampling, it may provide sufficient coverage for recording simultaneously from many sites within each individual brain, in order to explore the spatiotemporal dynamics of activity across different cortical areas
Our study addresses the spatiotemporal distribution of face information based on univariate measures, machine learningbased modeling, timing analysis, and direct cortical stimulation
Summary
We measured the fast temporal dynamics of face processing simultaneously across the human temporal cortex (TC) using intracranial recordings in eight participants. Some studies have revealed face-selective responses in anatomically discrete regions of the temporal cortex (TC)[5], and other observations have shown that the pattern of responses to face stimuli can be discerned from sampled data from nonselective regions of the TC17, suggesting that face information is anatomically distributed Both theories have relied on the information with limited temporal resolution averaged over multiple seconds or from methods using regions of interest and averaging across subjects, or direct recordings from a single or a pair of recording sites. Unlike the uniform spatial coverage of imaging methods, intracranial EEG (iEEG) relies on sampling from a limited number of implanted areas and leaves behind regions outside the coverage zones While this leads to limited anatomical sampling, it may provide sufficient coverage for recording simultaneously from many sites within each individual brain, in order to explore the spatiotemporal dynamics of activity across different cortical areas. The current study was designed to rely on a multiprong approach using univariate and multivariate methods of recording, as well as causal probing with electrical stimulation to test our proposed hypothesis
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