Prestimulus alpha phase modulates visual temporal integration
When presented shortly after another, discrete pictures are naturally perceived as continuous. The neuronal mechanism underlying such continuous or discrete perception are not well understood. While continuous alpha oscillations are a candidate for orchestrating such neuronal mechanisms, recent evidence is mixed. In this study, we investigated the influence of prestimulus alpha oscillation on visual temporal perception. Specifically, we were interested whether prestimulus alpha phase modulates neuronal and perceptual processes underlying discrete or continuous perception. Participant had to report the location of a missing object in a visual temporal integration task, while simultaneously MEG data was recorded. Using source reconstruction, we evaluated local phase effects by contrasting phase angle values between correctly and incorrectly integrated trials. Our results show a phase opposition cluster between - 0.8 to - 0.5 s (relative to stimulus presentation) and between 6 - 20 Hz. These momentary phase angle values were correlated with behavioural performance and event related potential amplitude. There was no evidence that frequency defined a window of temporal integration. Significance StatementIn light with the current debate if our visual perception is a rhythmic or discrete process, we give new insight to this debate. We investigated potential underling mechanism defining potential rhythmic perception and highlight the complexity of this process. This will help us further understand how our brain operates and processes incoming unimodal visual stimuli. In a visual temporal integration task, we were able to show that the incoming information were processed in rhythmic fashion. Our data supports the idea that the phase of prestimulus alpha oscillation modulates poststimulus visual processing by defining good and less good phases for early visual processes. We were not able to show that prestimulus alpha oscillation defines windows were two visual stimuli are integrated into one single event.