Alpha and gamma oscillations characterize feedback and feedforward processing in monkey visual cortex

TLDR

How low‑level and high‑level visual cortex areas interact during perception remains unresolved. We investigated whether cortical oscillations can distinguish feedforward from feedback processing. We examined propagation of α‑ and γ‑oscillations across cortical layers and areas, inducing them with microstimulation and modulating them pharmacologically. γ‑oscillations propagate feedforward while α‑oscillations propagate feedback, indicating that high‑ and low‑frequency oscillations serve as markers of feedforward and feedback processing.

Abstract

Significance One of the main unresolved questions in cognitive neuroscience is how low-level and high-level areas of the visual cortex interact with each other during perception and cognition. We investigated whether cortical oscillations can be used to distinguish feedforward from feedback processing. We studied the propagation of α- and γ-oscillations through the cortical layers and between different visual cortical areas. We induced oscillations in different areas with microstimulation and influenced them using a pharmacological approach. The results of these experiments demonstrate that γ-oscillations propagate in the feedforward direction, whereas α-oscillations propagate in the feedback direction. We conclude that high- and low-frequency oscillations provide markers of feedforward and feedback processing, respectively.