Rhythmic modulation of visual contrast discrimination triggered by action

Recent evidence suggests that ongoing brain oscillations may be instrumental in binding and integrating multisensory signals. In the present experiment, we investigated the temporal dynamics of visual-motor integration processes. We show that action modulates sensitivity to visual contrast discrimination in a rhythmic fashion at frequencies of about 5Hz (in the theta range), for up to one second after execution of action. To understand the origin of the oscillations, we measured oscillations in contrast sensitivity at different levels of luminance, which is known to affect the endogenous brain rhythms, boosting the power of alpha-frequencies. We found that the frequency of oscillation in sensitivity increased at low-luminance, likely reflecting the shift in mean endogenous brain rhythm towards higher frequencies. Importantly, both at high and at low luminance, contrast discrimination showed a rhythmic motor-induced suppression effect, with the suppression occurring earlier at low luminance. We suggest that oscillations play a key role in sensory-motor integration, and that the motor-induced suppression may reflect the first manifestation of a rhythmic oscillation.近期研究证据表明，持续的脑振荡（brain oscillations）可能在绑定与整合多感官信号过程中发挥关键作用。本实验中，我们探究了视运动整合（visual-motor integration）过程的时间动力学（temporal dynamics）特征。研究发现，动作执行后长达1秒的时间内，动作会以约5Hz（θ频段，theta range）的节律性方式调节视觉对比度辨别（contrast discrimination）的敏感度。为探明此类脑振荡的起源，我们测量了不同亮度（luminance）水平下的对比敏感度（contrast sensitivity）振荡——已知亮度可影响内源脑节律（endogenous brain rhythms），并提升α频段（alpha-frequencies）的振荡功率。结果发现，低亮度条件下敏感度振荡的频率升高，这大概率反映了内源脑平均节律向更高频段的偏移。值得注意的是，无论高亮度还是低亮度条件下，对比度辨别均表现出运动诱发的节律性抑制（rhythmic motor-induced suppression）效应，且低亮度时抑制效应出现的时间更早。我们提出，脑振荡在感觉运动整合中扮演核心角色，而运动诱发的抑制效应可能是节律性振荡的早期表现。