Individual Resting-state alpha peak frequency and within-trial changes in alpha peak frequency both predict visual flash segregation performance

Although sensory input is continuous, information must be combined over time to guide action and cognition, leading to the proposal of temporal sampling windows. A number of studies have suggested that a 10Hz sampling window might be involved in the "frame rate" of visual processing. To investigate this, we tested the ability of participants to localize and enumerate 1 or 2 visual flashes presented either at near-threshold (NT) or full contrast intensities, while recording magnetoencephalography (MEG). Performance was linked to the alpha frequency both at the individual level and trial-by-trial. Participants with a higher resting state alpha peak frequency showed the greatest improvement in performance as a function of ISI within the 100ms time window, while those with slower alpha improved more when ISI exceeded 100ms. On each trial, correct enumeration (1 vs. 2) performance was paired with faster pre-stimulus instantaneous alpha frequency. The effect of the timing of the NT stimulus on the perception was consistent with visual temporal integration windows being embedded in a sampling rhythm. Our results suggest that visual sampling/processing speed, linked to peak alpha frequency, is both an individual trait and varies in a state-dependent manner. Significance StatementA fundamental question in sensory and cognitive neuroscience is how the brain makes sense of the continuous flow of sensory input, parsing it into meaningful objects and events. The speed of cortical alpha rhythms is hypothesized to predict the temporal resolution of visual perception. We present a magnetoencephalography study investigating whether this temporal resolution is an individual trait or, in contrast, depends on fluctuations in brain state. Our results show that both individual resting state alpha frequency, a relatively stable trait, and trial-by-trial fluctuations of the instantaneous alpha frequency determine temporal segregation performance. These results have important implications for how our moment-by-moment perceptual experience is shaped as well as future intervention strategies to improve visual processing for specific tasks.