刺激前alpha振荡对视知觉的影响

人类对感觉阈限附近的视觉刺激的知觉不总是一致的。为探究这种视知觉不一致的现象及其神经机制, 一些研究者关注刺激前脑内自发alpha神经振荡(8~13 Hz)对视知觉的影响。近年来的研究发现, 刺激前alpha振荡能量的降低能提高被试的探测击中率, 但不能提高知觉精确度; 而刺激前alpha振荡的相位能预测被试能否成功探测刺激。刺激前alpha能量被认为调控了视皮层的基础活动强度; alpha能量的降低反映了皮层基础活动的增强, 进而提高了对较弱刺激的探测率。刺激前alpha相位则被认为调控了皮层兴奋和抑制的时间; 大脑在刺激呈现时的不同状态(兴奋/抑制)决定了最终的知觉结果。

The influences of prestimulus alpha oscillation on visual perception

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.