2005 Fiscal Year Final Research Report Summary
REPRESENTATION OF TIME IN THE BRAIN
| Project/Area Number |
15200031
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | JUNTENDO UNIVERSITY |
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Principal Investigator |
KITAZAWA Shigeru JUNTENDO UNIVERSITY, SCHOOL OF MEDICINE, PROFESSOR, 医学部, 教授 (00251231)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAZATO Taizo , 医学部, 講師 (80155697)
高橋 俊光 , 医学部, 助手 (00250704)
WADA Makoto , 医学部, 助手 (20407331)
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| Project Period (FY) |
2003 – 2005
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| Keywords | temporal order judgment / somatosensory signals / time cognition / fMRI / human / mouse / c-Fos |
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| Research Abstract |
It is known that the brain can resolve the order of two stimuli that are separated in time by as little as 30 ms. However, there is little consensus on how and where such discriminations are made. To elucidate how the brain orders sensory signals, we carried out a series of experiments with human and animal subjects. 1)We previously reported that temporal order judgment of two successive stimuli, delivered to the tips of sticks held in each hand, was altered by crossing the sticks without changing the positions of the hands. The previous report provided evidence for the referral of tactile signals to the tip of an actual tool in hand. In this study, we examined whether the referral occur to the tip, or action point, of a virtual tool for manipulating objects in the virtual reality with reaction force. The results suggest that somatosensory signals can be referred to the action point of a virtual tool that lacks any rigid body connecting the action point and the hand. 2)To elucidate whe
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re and how sensory signals are ordered in the brain, event-related functional magnetic resonance imaging (fMRI) was used while right-handed subjects judged the temporal order of two successive stimuli delivered one to each hand. Greater activation was elicited during the temporal order judgment than during the numerosity judgment in the following areas : bilateral posterior part of the middle temporal gyri (BA 37), bilateral premotor cortices (BA 6), bilateral inferior frontal gyri (BA 44), bilateral inferior parietal cortices (BA 40), and the left primary and secondary somatosensory cortices. The activation in the middle temporal gyri overlapped with the anterior part of the MT/V5.3) To study how somatosensory stimuli are ordered in the mouse brain, c-Fos production was examined in C57BL/6N mice that were trained to judge the order of two air-puff stimuli that were delivered to the right and the left whiskers. c-Fos expression was enhanced bilaterally in the task group as compared to the control group in the primary somatosensory cortex (barrel cortex), the paraventricular thalamic nucleus, the hypothalamus and the retrosplenial agranular cortex. c-Fos expression in the barrel cortex was most evident in the layers II and III, where callosal fibers originate from. Taken together, we infer that temporal order of tactile signals are ordered in time by combining representation of 'motion' in the temporal multimodal areas with the spatial representation of the stimuli in the frontal and parietal cortices. Less
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