1993 Fiscal Year Final Research Report Summary
Brain stem mechanisms for generation of vertical fast eye movement
| Project/Area Number |
04670062
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Hokkaido University |
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Principal Investigator |
FUKUSHIMA Kikurou Hokkaido University School of Medicine Associate Professor, 医学部, 助教授 (70091486)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Vestibular nystagmus / Semicircular canal / Eye movement / Midbrain / Interstitial nucleus of Cajal / Saccade / Cat |
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| Research Abstract |
It is well known that vestibular nystagmus evoked by head rotation occurs in the plane specific to that in which head rotation was applied in three-dimensional space. Although burster-driving neurons (BDN) habe been demonstrated for a quick phase of horizontal nystagmus (see Ref. 18), it is as yet unknown where the counterpart for vertical nystagmus is located. We searched for neurons in the rostral midbrain in alert cats that showed the characteristic discharge pattern required for BDNs(Kitama et al 1992) for vertical eye movement. Two groups of neurons were found in our study. Downward BDNs(n=48)received anterior canal excitation from the contralateral side with short latency ; upward BDNs(n=21) received posterior canal excitation. Mean lead time for the burst activity before fast eye movement was 30 msec for both saccades and vestibular fast phases for both groups of neurons. All of them had irregular resting discharge rates, and some showed eye positon sensitivity toward the direction opposite to their on-direction.
Downward BDNs were found in the interstitial nucleus of Cajal and its close vicinity ; whereas upward BDNs were found more laterally and caudally.
Bilateral muscimol infusion (0.3 mug for each side) into the downward BDN areas resulted in a selective loss of downward fast eye movement in addition to the failure of holding vertical eccentric eye position ; bilateral infusion into the upward BDN areas decreased number of upward fast eye movement significantly.
Horizontal eye movements were not impaired significantly by these imjections.
These results suggest specific involvement of vertical BDNs in generating vertical fast eye movement.
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