Abstract:

Human perception to near-threshold visual stimuli is not always reliable. To investigate variability of visual perception and its neural mechanism, some researchers focus on the influences of prestimulus ongoing alpha oscillations (8~13 Hz) on visual perception. Recently, studies found that decrease of prestimulus alpha power associated with improvement of observers’ detection rate, but no such effect on perception accuracy was found. In addition, phase of prestimulus alpha was reported to predict whether an observer can detect the following visual stimulus or not. Thus, power of prestimulus alpha is considered to reflect the excitability of visual cortex; decrease of alpha power indicates increase of cortical excitability, which results in higher detection rate of near-threshold stimuli. Nevertheless, phase of prestimulus alpha might play a role in regulating the time of excitation and inhibition of the cortex, and the different brain states (excitation or inhibition) at stimulus onset would lead to different perceptions of the stimulus.

Key words: prestimulus, neural oscillation, alpha power, alpha phase, visual perception