2005 Fiscal Year Final Research Report Summary
Role of visually guided saccades on initiation of reaching movement
| Project/Area Number |
16570196
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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 |
Anthropology
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| Research Institution | Kyorin University |
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Principal Investigator |
HIRAI Naoki Kyorin University, School of Medicine, Professor, 医学部, 教授 (40086583)
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| Project Period (FY) |
2004 – 2005
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| Keywords | eye movement / hand movement / saccade / tool-use / vision / somatosensory / reaching movement |
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| Research Abstract |
Direct comparison of onset times of saccades to 8 different targets revealed in man that the location of the stimulus has significant effect on the reaction times of saccades ; the shortest latencies were observed when the saccades directed towards right side, and then up-right direction. The slowest was produced in the purely downward saccades. The result raised a question: how the latency difference puts an influence on accuracy and reaction times of reaching movement toward different directions.
To answer this, eye and hand movements during reaching for food with hand-held tool in the monkey were studied while recording hand movement with Optotrack and video cameras and eye movement with magnetic search-coil technique. At the beginning, they transported hand-held forceps slowly toward food horizontally, but initially too short. With trials, the moving distance became longer and the forceps reached around the food with gradual increase of the speed. Prominent feature along with this m
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ovement was that hand movement did not cooperate with gaze-shift although the view of the food was open. They gradually changed the maneuver. They began to make a gaze-shift to the food but at variable timing relative to the contact of the forceps at food. Some were made only after contact, others in the transporting phase of hand. The results showed that movements were learned mainly with the aid of proprioceptions, and visual information was used for fine placement of the forceps. Finally, eye and hand movements cooperated as in bear hand. However, at this stage, when vision was interrupted by liquid crystal shutter at the initiation of hand movement, monkeys stopped transporting their hand, although they could retrieve food by their bear hand. This shows that monkeys have the ability to represent internally the invisible object and that they had to make new motor programs which were lacking initially, and eventually acquired through practice. In an extreme task, monkey managed to take food without vision. Less
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