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

本研究考察了无意识知觉和运动反应下信息加工的本质，使用反应时(RT)任务和后向掩蔽范式进行了几个实验，其中以主刺激和掩蔽刺激作为命令刺激。在实验中，主刺激的强度和SOA(主刺激和掩蔽刺激之间的刺激开始不同步)都被操纵。为了考察行为方面，我们测量了(1)在两个强迫选择任务中对首要刺激的知觉，(2)作为对命令性刺激集(首要刺激和掩蔽刺激)的运动反应的反应时间，以及(3)根据平均脑电波计算的偏侧就绪电位(LRP)。实验结果表明，反应时间与S-LRPS的潜伏期(从刺激开始到LRPs最初升高的经过时间)有关，而R-LRPs的潜伏期(从LRPS开始到反应开始的经过时间)与反应时间无关。这表明，主刺激在运动信息加工阶段较早地启动了运动反应的准备阶段。对主刺激的知觉在长刺激(100ms)时很明显，但在短刺激(32ms)中消失，说明短刺激(32ms)必须被掩蔽刺激所掩盖。对于32毫秒的SOA，S-LRP的潜伏期与S-LRP的潜伏期非常相似，在这种条件下，只有一个主刺激被呈现为强制性刺激。这表明，潜意识中感知到的主要刺激。促进运动反应，导致反应时间较短。然而，主刺激是否促进了知觉过程，或者更确切地说，是直接激活了绕过知觉过程的运动过程，这一问题仍然有待商榷。

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.