2002 Fiscal Year Final Research Report Summary
Properties of Eye-Head Co-ordination during Visually Guided Gaze Shifts in Humans
| Project/Area Number |
12640698
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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 |
人類学(含生理人類学)
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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) |
2000 – 2002
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| Keywords | saccade / orienting reflex / eye movements / reaction time |
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| Research Abstract |
Latencies of visually guided saccades (SRTs) are shortened by 100ms when a gap task (target appears 200ms after disappearance of the fixation point FP) is introduced. Why the shortest reaction is hidden in everyday life was the main theme of the present project. In the first experiment, SRTs were measured while a color of the FP was changed from red to green prior to the peripheral target appearance (RG paradigm), to understand the role of the FP offset in saccade initiation. The RG paradigm fastened SRTs relative to the conventional tasks. In the second experiment, coupling between eye and head motor systems during gaze shifts were examined. When the reflexive (target-directed) and voluntary (anti-target-directed) tasks were interleaved, subjects made directional errors in the initial head movements alone in some occasions; diverged incorrect head and correct eye movements. The results are contrast to the commonly held view that there is a tight coupling between head and eye during gaze shifts, and suggest that both are controlled independently in humans. Comparison of the coupling between both motor systems is more flexible in the order of human, monkey and cat. The final experiment examined whether any downward saccades across the lower visual field show uniformly slow onset time, because a disadvantage for downward saccade as compared with upward saccade has been explained from ecological viewpoints. The mean latency of purely downward saccades was significantly longer than that of purely horizontal saccades. However, latency of horizontal or downward components of oblique saccades was as fast as the purely horizontal saccades. The result indicates that there exists an apparent SRT bias within the lower visual field. The properties of human gaze shifts came to light from these results.
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