title: Differential visually-induced gamma-oscillations in human cerebral cortex.
abstract: Using intracranial electrocorticography, we determined how cortical gamma-oscillations (50-150 Hz) were induced by different visual tasks in nine children with focal epilepsy. In all children, full-field stroboscopic flash-stimuli induced gamma-augmentation in the anterior-medial occipital cortex (starting on average at 31 ms after stimulus presentation) and subsequently in the lateral-polar occipital cortex; minimal gamma-augmentation was noted in the inferior occipital-temporal cortex; occipital gamma-augmentation was followed by gamma-attenuation in three children. Central-field picture-stimuli induced sustained gamma-augmentation in the lateral-polar occipital cortex (starting on average at 69 ms) and subsequently in the inferior occipital-temporal cortex in all children and in the posterior frontal cortex in three children; the anterior-medial occipital cortex showed no gamma-augmentation but rather gamma-attenuation. Electrical stimulation of the anterior-medial occipital cortex induced a phosphene in the peripheral-field or eye deviation to the contralateral side, whereas that of the lateral-polar occipital cortex induced a phosphene in the central-field. In summary, full-field, simple and short-lasting visual information might be preferentially processed by the anterior-medial occipital cortex, and subsequently by the lateral-polar occipital cortex. Gamma-attenuation following augmentation in the striate cortex might be associated with a relative refractory-period to flash-stimuli or feed-forward inhibition by other areas. Central-field complex visual information might be processed by a network involving the lateral-polar occipital cortex and the inferior occipital-temporal cortex. A plausible interpretation of posterior frontal gamma-augmentation during central-field picture stimuli includes activation of the frontal-eye-field for visual searching. Gamma-attenuation in the anterior-medial occipital cortex during central-field picture-stimuli might be associated with relative inattention to the peripheral visual field during central-field object visualization.
authors.affiliation: Division of Pediatric Neurology, Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, Michigan 48201, USA. eishi@pet.wayne.edu
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nishida
authors.forename: Miho
authors.initials: M
authors.lastname: Fukuda
authors.forename: Robert
authors.initials: R
authors.lastname: Rothermel
authors.forename: Csaba
authors.initials: C
authors.lastname: Juhász
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sood
mesh_terms: D000293:Adolescent; D001683:Biological Clocks; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D004562:Electrocardiography / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology*; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods*; D049489:Stroboscopy / Q000379:methods