Stimulus-induced gamma power predicts the amplitude of the subsequent visual evoked response
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PI Group Neurobiology of Language
Key wordsMEG; Evoked activity; Visual cortex; Oscillation; Gamma; Synchronization
The efficiency of neuronal information transfer in activated brain networks may affect behavioral performance.Gamma-band synchronization has been proposed to be a mechanism that facilitates neuronal processing ofbehaviorally relevant stimuli. In line with this, it has been shown that strong gamma-band activity in visualcortical areas leads to faster responses to a visual go cue. We investigated whether there are directly observableconsequences of trial-by-trial fluctuations in non-invasively observed gamma-band activity on the neuronalresponse. Specifically, we hypothesized that the amplitude of the visual evoked response to a go cue can bepredicted by gamma power in the visual system, in the window preceding the evoked response. Thirty-threehuman subjects (22 female) performed a visual speeded response task while their magnetoencephalogram(MEG) was recorded. The participants had to respond to a pattern reversal of a concentric moving grating. Weestimated single trial stimulus-induced visual cortical gamma power, and correlated this with the estimated singletrial amplitude of the most prominent event-related field (ERF) peak within the first 100 ms after the patternreversal. In parieto-occipital cortical areas, the amplitude of the ERF correlated positively with gamma power, andcorrelated negatively with reaction times. No effects were observed for the alpha and beta frequency bands,despite clear stimulus onset induced modulation at those frequencies. These results support a mechanistic model,in which gamma-band synchronization enhances the neuronal gain to relevant visual input, thus leading to moreefficient downstream processing and to faster responses.