Backward masking in a somatosensory reaction-time task and nonconscious motor information-processing

本研究项目考察了无意识知觉和运动反应下信息加工的本质，采用逆向掩蔽范式的反应时间（RT）任务进行了几个实验，其中启动刺激和掩蔽刺激被用作命令性刺激。实验中对启动刺激的强度和启动刺激与掩膜刺激之间的非同步性进行了控制。为了研究行为方面，我们测量了(1)在双强迫选择任务中对启动刺激的感知意识，(2)对必要刺激集（启动和面具）的运动反应时间，以及(3)根据平均脑电波计算的侧化准备电位（lrp）。实验结果表明，反应时间倾向于与s - lrp潜伏期（从刺激开始到lrp初始上升的时间）相关，而r - lrp潜伏期（从lrp开始到反应开始的时间）与反应时间无关。这表明，启动刺激较早地启动了运动信息加工阶段，以准备运动反应。长SOA （100 ms）对启动刺激的感知意识是明显的，而短SOA （32 ms）对启动刺激的感知意识是不存在的，这表明启动刺激一定被短SOA （32 ms）的掩模刺激所掩盖。在32毫秒的SOA条件下，s - lrp的延迟与单独将启动刺激作为命令刺激时的s - lrp的延迟非常相似。这表明无意识地感知到启动刺激。促进运动反应，导致反应时间短。然而，究竟是启动刺激促进了知觉过程，还是绕过知觉过程直接激活了运动过程，这一问题仍有待探讨。

This research project examined the nature of information processing underlying perception without awareness and motor responses, conducting several experiments using reaction time (RT) tasks with a backward masking paradigm in which a prime and mask stimuli were used as imperative stimuli. Both the intensity of the prime stimulus and SOA (stimulus onset asynchrony between the prime and mask stimulus) were manipulated in the experiments. To examine behavioral aspects we measured (1)the awareness of perception of the prime stimulus in a two-forced-choice task, (2)reaction times as motor responses to the imperative stimulus set (prime and mask), and (3) lateralized readiness potentials (LRPs) which were calculated on the basis of averaged EEG waves.Results of experiments showed that reaction times tended to be correlated with the latency of S-LRPs (the elapsing time from the stimulus onset to the initial raise of the LRPs), whereas the latency of R-LRPs (the elapsing time from the onset of LRPs to the onset of responses) was not correlated with reaction times. This suggested that the prime stimulus initiated earlier the stage of motor information processing for the preparation of motor responses. Awareness of perception of the prime stimulus was evident for a long SOAs (100 ms) but was absent for a short SOAs (32 ms), indicating the prime stimulus must be masked by the mask stimulus with the short (32-ms) SOA. The latency of S-LRPs for the 32-ms SOA was quite similar to that of the S-LRPs under conditions where a prime stimulus alone was presented as an imperative stimulus. This suggested that non-consciously perceived prime stimulus. facilitated motor responses, resulting in short reaction times. However, an issue whether the prime stimulus facilitates the perceptual processes or rather directly activates the motor processes bypassing the perceptual processes, was still open to question.