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Memory and Temporal Cognition

開催日 2014/9/13
時間 10:00 - 11:00
会場 Room H(304)
Chairperson(s) 定藤 規弘 / Norihiro Sadato (自然科学研究機構 生理学研究所 大脳皮質機能研究系 / Department of Cerebral Research, National Institute for Physiological Sciences, Japan)
北澤 茂 / Shigeru Kitazawa (大阪大学大学院生命機能研究科 / Osaka University, Graduate School of Frontier Biosciences, Japan)

Alpha-phase dependent reversal of tactile temporal order judgment

  • O3-H-2-3
  • 高橋 俊光 / Toshimitsu Takahashi:1,2 北澤 茂 / Shigeru Kitazawa:1,2 
  • 1:大阪大学大学院生命機能研究科 / Dynamic Brain Network Laboratory Graduate School of Frontier Biosciences, Osaka University, Japan 2:大阪大学大学院医学研究科 / Department of Brain Physiology, Graduate School of Medicine, Osaka University, Japan 

  Temporal order judgment (TOJ) of two successive tactile stimuli that are delivered one to each hand is often reversed when the arms are crossed. The process has been modelled as probabilistic, but it remains unknown what determines the probability. We previously proposed that a kind of "motion" signal generated by the successive stimuli plays an essential role in TOJ and its reversal. On the other hand, it has been reported that perception of "apparent motion" depends on the pre-stimulus phase of cortical alpha-rhythms (Valera et al., 1981). Base on these previous studies, we hypothesized that the pre-stimulus alpha-rhythm affects the probability of judgment reversal through its modulatory effects on the motion signal.
  To test the hypothesis, we recorded cortical activity by using a 160-ch magnetometer (Yokogawa) from 9 healthy right-handed volunteers, while the participants carried out a tactile TOJ task with their arms crossed. Each run consisted of 200 trials, in which stimuli were delivered to the right hand and then to the left hand, or in the reverse order in a pseudorandom manner. Stimulus onset asynchrony (SOA) was fixed to 100 ms.
  The rate of judgment reversal was 0.50 on average, 0.64 for the left-hand first stimuli, and 0.36 for the right-hand first stimuli. We used independent component analysis to choose a component with the largest alpha power, and compared pre-stimulus alpha phase of the component in trials with correct judgment and those with inverted judgments. As a result, we found that the pre-stimulus phase in the alpha-rhythm was significantly different between the correct and inverted trials in 6 participants, when the left-hand stimulus preceded the right hand stimulus (mean p value < 0.00001).
  The results suggest that pre-stimulus alpha-phase partly determines the probability of judgment reversal through its modulatory effects on generating motion signals from successive sensory stimuli.

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