Gamma oscillations in visual cortex have been hypothesized to be critical for perception, cognition, and information transfer. However, observations of these oscillations in visual cortex vary widely; some studies report little to no stimulus-induced narrowband gamma oscillations, others report oscillations for only some stimuli, and yet others report large oscillations for most stimuli. To better understand this signal, we developed a model that predicts gamma responses for arbitrary images and validated this model on electroco rticography (ECoG) data from human visual cortex. The model computes variance across the outputs of spatially pooled orientation channels, and accurately predicts gamma amplitude across 86 images. Gamma responses were large for a small subset of stimuli, differing dramatically from f MRI and ECoG broadband (non-oscillatory) responses. We propose that gamma oscillations in visual cortex serve as a biomarker of gain control ratherthan being a fundamental mechanism for communicating visual information.
Bibliographical noteFunding Information:
This work was supported by the Dutch Organization for Scientific Research grant 016.VENI.178.048 to DH and the National Institute of Mental Health grant R01MH111417-01 to JW and NP. The authors thank the Parvizi lab at Stanford, the Stanford Human Intracranial Cognitive Electrophysiology Program (SHICEP), and the Ramsey lab, Cyrille Ferrier and the neurophysiology team at the UMC Utrecht for their help in recording the ECoG data, and we thank David Heeger for helpful discussions and comments on an earlier draft of the manuscript and we thank Pascal Fries for helpful suggestions on an earlier version of this manuscript.