title: Stimulus Dependence of Gamma Oscillations in Human Visual Cortex.
abstract: A striking feature of some field potential recordings in visual cortex is a rhythmic oscillation within the gamma band (30-80 Hz). These oscillations have been proposed to underlie computations in perception, attention, and information transmission. Recent studies of cortical field potentials, including human electrocorticography (ECoG), have emphasized another signal within the gamma band, a nonoscillatory, broadband signal, spanning 80-200 Hz. It remains unclear under what conditions gamma oscillations are elicited in visual cortex, whether they are necessary and ubiquitous in visual encoding, and what relationship they have to nonoscillatory, broadband field potentials. We demonstrate that ECoG responses in human visual cortex (V1/V2/V3) can include robust narrowband gamma oscillations, and that these oscillations are reliably elicited by some spatial contrast patterns (luminance gratings) but not by others (noise patterns and many natural images). The gamma oscillations can be conspicuous and robust, but because they are absent for many stimuli, which observers can see and recognize, the oscillations are not necessary for seeing. In contrast, all visual stimuli induced broadband spectral changes in ECoG responses. Asynchronous neural signals in visual cortex, reflected in the broadband ECoG response, can support transmission of information for perception and recognition in the absence of pronounced gamma oscillations.
authors.affiliation: Department of Psychology, New York University, New York, NY, USA Department of Psychology, Stanford University, Stanford, CA, USA.
authors.forename: D
authors.initials: D
authors.lastname: Hermes
authors.affiliation: Department of Neurosurgery, Stanford University, Stanford, CA, USA Program in Neurobiology and Behavior, University of Washington, Seattle, WA, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Miller
authors.affiliation: Department of Psychology, Stanford University, Stanford, CA, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Wandell
authors.affiliation: Department of Psychology, New York University, New York, NY, USA Center for Neural Science, New York University, New York, NY, USA.
authors.forename: J
authors.initials: J
authors.lastname: Winawer
mesh_terms: D001931:Brain Mapping; D004569:Electroencephalography; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D010100:Oxygen / Q000097:blood; D013057:Spectrum Analysis; D013997:Time Factors; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: broadband spectral change; electrocorticography; gamma oscillations; human electrophysiology; visual cortex