Spatiotemporal dynamics and functional correlates of evoked neural oscillations with different spectral powers in human visual cortex

Objective: To investigate spatiotemporal characteristics and functional correlates of evoked oscillations (EOs) at different frequency bands in human visual cortex. Methods: Flash visual evoked potentials (FVEPs) were recorded from 11 epilepsy patients with intracranial electrodes placed over the occipital and adjacent cortices. Spatiotemporal characteristics of spectral powers and correlation with various visual responses elicited by electrical cortical stimulations were analyzed in the same electrodes. Results: High gamma (60-150 Hz) EOs were first recorded in the cuneus and lingual gyri around the calcarine sulcus. Low gamma (30-60 Hz) EOs appeared also in the mesial occipital cortex slightly later and lasted longer than high gamma EGOs. In contrast, lower frequency (LF) < 30 Hz EOs were recorded more diffusely from occipital surfaces with delayed onset and longer duration. High gamma EOs were predominantly associated with simple form visual responses, whereas low gamma and LF EOs were with intermediate form and LF EOs with complex form responses. Conclusions: FVEP spectral power analysis directly recorded from human visual cortex showed distinct spatiotemporal distributions in high and low gamma, or LF bands that have different functional correlates. Significance: Phase-locked EOs in these frequency bands may have special neuroanatomical and functional organization during early visual processing. Crown Copyright (C) 2013 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology