2003 Fiscal Year Final Research Report Summary
Backward masking in a somatosensory reaction-time task and nonconscious motor information-processing
| Project/Area Number |
13680039
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
体育学
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
IMANAKA Kuniyasu Tokyo Metropolitan University, Kinesiology, Professor, 理学研究科, 教授 (90100891)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIHIRA Yoshiki University of Tsukuba, Health & Sport Science, Professor, 体育科学系, 教授 (20156095)
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| Project Period (FY) |
2001 – 2003
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| Keywords | reaction time / stimulus detection / awareness of perception / motor preparation / backward masking / nonconscious processing / information processing |
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| Research Abstract |
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.
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