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 γ (60-150. Hz) EOs were first recorded in the cuneus and lingual gyri around the calcarine sulcus. Low γ (30-60. Hz) EOs appeared also in the mesial occipital cortex slightly later and lasted longer than high γ EGOs. In contrast, lower frequency (LF) <30. Hz EOs were recorded more diffusely from occipital surfaces with delayed onset and longer duration. High γ EOs were predominantly associated with simple form visual responses, whereas low γ 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 γ, 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.