December 2002
Volume 43, Issue 13
Free
ARVO Annual Meeting Abstract  |   December 2002
Disconjugate Eye Movements Evoked by Electrical Micro-Stimulation of the Rostral Superior Colliculus in the Alert Cat
Author Affiliations & Notes
  • S Suzuki
    Department of Ophthalmology Sapporo Medical University Sapporo Japan
  • Y Suzuki
    Department of Ophthalmology Sapporo Medical University Sapporo Japan
  • M Sawa
    Department of Ophthalmology Sapporo Medical University Sapporo Japan
  • K Ohtsuka
    Department of Ophthalmology Sapporo Medical University Sapporo Japan
  • Footnotes
    Commercial Relationships   S. Suzuki, None; Y. Suzuki, None; M. Sawa, None; K. Ohtsuka, None. Grant Identification: the Japanese Ministry of Education, Science, Sports, and Culture (13470370)
Investigative Ophthalmology & Visual Science December 2002, Vol.43, 1489. doi:
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      S Suzuki, Y Suzuki, M Sawa, K Ohtsuka; Disconjugate Eye Movements Evoked by Electrical Micro-Stimulation of the Rostral Superior Colliculus in the Alert Cat . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1489.

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Abstract

Abstract: : Purpose: The rostral pole of the superior colliculus (rostral SC) has been considered as one of the supra-nuclear center for fixation. Recently, the rostral SC is also postulated to be involved in the control of accommodation in the cat (Ohtsuka et al, 1994, 1996, 1997). Descending projection from the lateral supra-sylvian area (LS cortex), in which ocular convergence and lens accommodation could be evoked by micro-stimulation (Bando et al, 1996), to the rostral SC was shown anatomically in the cat (Ohtsuka and Sato, 1996). These recent investigations suggested that the rostral SC could be involved in the control system for vergence eye movements. To confirm the role of the rostral SC for vergence, we stimulated the rostral SC electrically and induced disconjugate horizontal eye movements in two alert cats. Methods: Binocular eye movements were recorded using magnetic search coils sutured on the sclera. The SC was identified by the single unit activity correlated with visual stimuli and saccades. The current intensity, pulse rate and duration were systematically varied in the range of 10-40µA, 125-500 Hz and 125-500 msec, respectively. Results: In 9 of 27 tracts at the rostral SC, disconjugate eye movements were evoked by the electrical stimulation with the threshold less than 20µA, however, disconjugate eye movements were not evoked by the stimulation at the caudal SC. Evoked disconjugate eye movements were in the direction of convergence and the most of them were accompanied with conjugate eye movements toward contra-lateral direction. Average latency and amplitude of the evoked disconjugate eye movements were 83±47msec and 1.3±0.4deg. Amplitude of the evoked disconjugate eye movements were positively correlated with intensity of the electrical stimulation, and negatively correlated with the initial vergence eye position. Conclusions: These results suggest that the rostral SC is involved in the control system of vergence eye movements. Because the involvements of the rostral SC in the control system for accommodation was also shown, this area might be the center of the near response. CR: none. Support: the Japanese Ministry of Education, Science, Sports, and Culture (13470370)

Keywords: 617 vergence • 593 superior colliculus/optic tectum • 406 eye movements 
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