Modelling the effects of ongoing alpha activity on visual perception: The oscillation-based probability of response.

Substantial evidence has shown that ongoing neural activity significantly contributes to how the brain responds to upcoming stimuli. In visual perception, a considerable portion of trial-to-trial variability can be accounted for by prestimulus magneto/electroencephalographic (M/EEG) alpha oscillations, which play an inhibitory function by means of cross-frequency interactions with gamma-band oscillations. Despite the fundamental theories on the role of oscillations in perception and cognition, the current literature lacks a clear theorization of the neural mechanisms underlying the effects of prestimulus activity, including electrophysiological phenomena at different scales (e.g., local field potentials and macro-scale M/EEG). Here, we present a model called the oscillation-based probability of response (OPR), which directly assesses the link between meso-scale neural mechanisms, macro-scale M/EEG, and behavioural outcome. The OPR includes distinct meso-scale mechanisms through which alpha oscillations modulate M/EEG gamma activity, namely, by decreasing a) the amplitude and/or b) neural synchronization of gamma oscillations. Crucially, the OPR makes specific predictions on the effects of these mechanisms on visual perception, as assessed through the psychometric function. SIGNIFICANCE STATEMENT: The oscillation-based probability of response (OPR) is grounded on a psychophysical approach focusing on the psychometric function estimation and may be highly informative in the study of ongoing brain activity, because it provides a tool for distinguishing different neural mechanisms of alpha-driven modulation of sensory processing.