title: Independent predictors of neuronal adaptation in human primary visual cortex measured with high-gamma activity.
abstract: Neuronal adaptation is defined as a reduced neural response to a repeated stimulus and can be demonstrated by reduced augmentation of event-related gamma activity. Several studies reported that variance in the degree of gamma augmentation could be explained by pre-stimulus low-frequency oscillations. Here, we measured the spatio-temporal characteristics of visually-driven amplitude modulations in human primary visual cortex using intracranial electrocorticography. We determined if inter-stimulus intervals or pre-stimulus oscillations independently predicted local neuronal adaptation measured with amplitude changes of high-gamma activity at 80-150 Hz. Participants were given repetitive photic stimuli with a flash duration of 20 μs in each block; the inter-stimulus interval was set constant within each block but different (0.2, 0.5, 1.0 or 2.0s) across blocks. Stimuli elicited augmentation of high-gamma activity in the occipital cortex at about 30 to 90 ms, and high-gamma augmentation was most prominent in the medial occipital region. High-gamma augmentation was subsequently followed by lingering beta augmentation at 20-30 Hz and high-gamma attenuation. Neuronal adaptation was demonstrated as a gradual reduction of high-gamma augmentation over trials. Multivariate analysis demonstrated that a larger number of prior stimuli, shorter inter-stimulus interval, and pre-stimulus high-gamma attenuation independently predicted a reduced high-gamma augmentation in a given trial, while pre-stimulus beta amplitude or delta phase had no significant predictive value. Association between pre-stimulus high-gamma attenuation and a reduced neural response suggests that high-gamma attenuation represents a refractory period. The local effects of pre-stimulus beta augmentation and delta phase on neuronal adaptation may be modest in primary visual cortex.
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan 48201, USA.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matsuzaki
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Nagasawa
authors.forename: Csaba
authors.initials: C
authors.lastname: Juhász
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sood
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D001683:Biological Clocks / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D007223:Infant; D007266:Inhibition, Psychological; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D014793:Visual Cortex / Q000502:physiology*