| Co-Investigator(Kenkyū-buntansha) |
MURAMOTO Ken-ichiro Kanazawa Univ., Fac. Technol., Associate professor, 工学部・電気情報工学科, 助教授 (70042835)
TAMURA Ryoi Toyama Med. & Pharmaceu. Univ. Fac. Med., Assistant professor, 医学部, 助手 (60227296)
NISHIJO Hisao Toyama Med. & Pharmaceu. Univ. Fac. Med., Assistant professor, 医学部, 助手 (00189284)
FUKUDA Masaji Toyama Med. & Pharmaceu. Univ. Fac. Med., Associate professor, 医学部, 助教授 (60126547)
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| Research Abstract |
In this project, hippocampal neuronal activity of awake monkey during discrimination of loci, objects, and events (Study 1), and effects of ischemic neuronal death confined to the monkey hippocarnpus on memory (Study 2) were investigated. In Study 1, a total of 2169 neurons were recorded from the hippocampal formation and surrounding parahippocampal gyrus of awake monkeys while the monkey discriminated various familiar rewarding and aversive objects as well as unfamiliar objects (paradigm 1 ; n=1911), and while the monkey actively controlled the cab to change its location within a 2.5x2.5 m region (paradigm 2 ; n=258). In paradigm 1, visually responsive neurons (n=160) were categorized into the following, based on their responsiveness to biological significance of the objects ; rewarding-object-dominant, aversive-object-dominant, and unfamiliar-object-dominant neurons. In paradigm 2, activity of 165 (64.0%) changed in response to direction related stimuli, or location of the cab contai
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ning the subject, or presentation of objects (food or nonfood). Of 165 responding neurons, 41 responded to a particular stimulus presented from a specific direction (direction-related). Responses of these neurons could be described in terms of egocentric or allocentric coordinates, or combinations of these coordinates. Increase or decrease of spontaneous activity of 79 neurons depended on the animal's specific location within the 2.5x2.5 m field (place-related). The 119 neurons responded in one or more phase (s) of a task that involved cue signals, moving by holding the bar, or reward presentation upon opening of a shutter (task-related). Some of these neurons showed specific combinations of directional, placerelated, and task-related responses.
In Study 2, the monkey subjected to 10-15 min occlusion of 8 (bilateral common carotid, intemal and extemal carotid, and vertebral) major arteries suffered ischemic cell changes restricted to the CA1 subfield of the hippocampus. These monkeys with ischemic insult indicated significant memory disturbance in a delayed non- matching to sample test, while no deficits in motor-skill nor simple visual discrimination task were evident. The intravenous infusion of a calcium blocker (NC-1100) significantly ameliorated ischemic cell changes in the monkey hippocampus. Less
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