Face-selective spectral changes in the human fusiform gyrus

Objective: To characterize ventral occipitotemporal and prefrontal EEG duri ng cognitive processing. Methods: Depth probes were implanted for seizure localization in 16 pharmac o-resistant epileptics. Probes penetrated from middle temporal through fusi form to lingual gyrus, and from inferior frontal to anterior cingulate gyru s, Event-related potentials (ERPs) and event-related spectral power (ERSP) were calculated during delayed recognition for faces or words. Results: Face stimuli evoked a broadband fusiform ERSP increase from 5 to 4 5 Hz at 150-210 ms after stimulus onset. This ERSP increase was immediately followed by an ERSP decrease in the same region from 300 to 1000 ms. Both the early increased ERSP and the late decreased ERSP, were greater for face s than words. Simultaneous with the late temporal ERSP decrease, the prefro ntal depth EEG displayed a low frequency (5-12 Hz) ERSP increase to face an d word stimuli. Conclusion: Early temporal ERSP increases occur at a time when the fusiform gyrus is thought to contribute to face processing. This increase is also r eflected in spectral analysis of the ERP, but the late temporal ERSP decrea se and frontal ERSP increase are not. Thus, intracranial recordings in huma ns demonstrate event-related fluctuations in EEG spectral power with clear anatomical, temporal and cognitive specificity. (C) 1999 Elsevier Science I reland Ltd. All rights reserved.