Subliminal stimulation alters conscious perception – a potential mechanism is the modulation of cortical background rhythms especially in the alpha range. Here, in the human somatosensory domain, we assessed effects of subthreshold (imperceptible) electrical finger nerve stimulation – either presented as single pulses or as brief (1 s) 7 Hz pulse trains—on mu-alpha rhythm and perceptual performance. In electroencephalography, subthreshold single pulses transiently (~150–350 ms poststimulus) increased mu activity (event-related synchronization), while, interestingly, subthreshold trains led to prolonged (>1 s) mu desynchronization. In psychophysics, detection of near-threshold target stimuli was consistently reduced when presented together with subthreshold trains (at three delays), whereas for targets paired with subthreshold single pulses detection remained unaffected (30 and 180 ms) or was even elevated (60 ms). Though both imperceptible, single pulses and pulse trains exerted opposite effects on neural signaling and perception. We suggest that the common neural basis is preferential activation of cortical inhibitory interneurons. While the inhibitory impact of a subthreshold single pulse (reflected by mu synchronization) is not psychophysically detectable—rather perception may be facilitated—repetition of the same subthreshold pulse shifts the excitation-inhibition balance toward an inhibitory cortical state (reflected by perceptual impediment) accompanied by mu desynchronization. These differential findings provide novel insights on the notion of alpha activity mediating functional inhibition.

中文翻译：

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不可察觉的体感单脉冲和脉冲序列刺激相反地调节 Mu 节律活动和知觉表现。

潜意识刺激会改变有意识的感知——一种潜在的机制是调节皮质背景节律，尤其是在 alpha 范围内。在这里，在人类体感领域，我们评估了阈下（不可察觉的）手指神经电刺激 - 以单脉冲或短暂（1 秒）7 Hz 脉冲序列的形式出现 - 对 mu-alpha 节律和感知性能的影响。在脑电图中，亚阈值单脉冲瞬时（~150-350 ms 刺激后）增加 mu 活动（事件相关同步），而有趣的是，亚阈值序列导致长时间（> 1 s）mu 不同步。在心理物理学中，当与亚阈值序列（三个延迟）一起呈现时，对近阈值目标刺激的检测持续减少，而对于与亚阈值单脉冲检测配对的目标，检测仍然不受影响（30 和 180 毫秒），甚至有所提高（60 毫秒）。虽然都难以察觉，但单脉冲和脉冲序列对神经信号和感知产生了相反的影响。我们认为共同的神经基础是皮质抑制性中间神经元的优先激活。虽然亚阈值单脉冲的抑制作用（由 mu 同步反映）在心理物理学上是不可检测的——而是可以促进感知——重复相同的亚阈值脉冲会将兴奋-抑制平衡转移到抑制性皮质状态（由感知障碍反映）伴随通过 mu 去同步。这些不同的发现提供了关于 α 活性介导功能抑制的概念的新见解。