1997 Fiscal Year Final Research Report Summary
Analysis of visuo-motor transformation process in the tecto-reticulo-spinal system.
| Project/Area Number |
08458266
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
神経・脳内生理学
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| Research Institution | National Institute for Physiological Sciences, Okazaki National Research Institutes |
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Principal Investigator |
ISA Tadashi National Institute for Physiological Sciences, Department of Integrative Physiology, Professor, 生理学研究所, 教授 (20212805)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Yasuhiko National Institute for Physiological Sciences, Department of Integrative Physio, 生理学研究所, 助手 (70290913)
AIZAWA Hiroshi National Institute for Physiological Sciences, Department of Integrative Physiol, 生理学研究所, 助手 (40222434)
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| Project Period (FY) |
1996 – 1997
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| Keywords | attention / express saccades / superior colliculus / acetylcholine / nicotine / monkey / rats / サル |
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| Research Abstract |
Reaction time of visually guided saccadic eye movements can be a good measure to monitor the state of spatial attention.
When our attention on a fixation point in the center of our vesual field is desengaged, and becomes diffused on the periphery of the visual field, extremely short-latency saccadic eye movements (70-100msec after presentation of the target), called express saccades, occur to targets presented in the periphery. We have hypothesized that the express saccades take place when the visual input directly activate the motor output system by taking the short-cut pathway in the central nervous system, and the short-cut pathway is that from the superficial layr to the deeper layrs of the superior colliculus (SC). Furthermore, we hypothesized that acetylcholinergic system plays the dey role in facilitating the signal transmission in the SC to execute the express saccades.
To prove these hypotheses, we investigated (1) signal transmission in the local circuit of the SC and function
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of acetylcholinergic input by using slice preparations obtained from rats, and (2) effect of injection of acetylcholine-related substance (especially nicotine) into the SC on saccadic reaction time.
(1) We have clarified that there exists an excitatory pathway from the optic tract (OT) to the intermediate layr (SGI) of the SC via neurons in the superficial (SGS) and optic (SO) layrs by suing whole cell patch clamp recording technique in the SC slices obtained from rats. The excitatory transmission in mediated by both AMPA and NMDA type glutamate receptors, and usually under strong suppression by the GABAA system. Nicotine induces inward currents in neurons in the intermediate layr of the SC,by direct action on the nicotinic receptors in these neurons. Furthermore, application of nicotine dramatically enhanced the signal transmission in the OT-SGS/SO-SGI pathway, which was attriuted to the depolarization of the SGI neurons by nicotine.
(2) When nicotin (1-10mM,1mul) is injected into the SGI of the monkey SC (n=2), frequency of express saccades (latency below 100 msec) dramatically increased. The mechanisms was supposed to be bypassing the short-cut pathway from the SGS/SO to the SGI neurons by depolarizing the SGI neurons.
We are further planning to investigate the effect of acetylcholine antagonists on occurrence of express saccades and activity of cholinergic neurons in the pedunclulopontine tegmental nucleus, which is the input origin of the cholinergic fibers innervating the SC during visually guided saccade task. Less
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Research Products
(11 results)
