Neuroscience 2000 Abstract
| Presentation Number: | 8.10 |
|---|---|
| Abstract Title: | Kinematics of active control of rectus extraocular muscle pulleys. |
| Authors: |
Demer, J. L.*1
1Jules Stein Eye Inst & Dept of Neurology, UCLA Med Sch, Los Angeles, CA |
| Primary Theme and Topics |
G. Motor Systems and Sensorimotor Integration - 90. Oculomotor system |
| Secondary Theme and Topics | G. Motor Systems and Sensorimotor Integration<br />- 97. Muscle and motor units |
| Session: |
8. Vestibular system: vestibular and oculomotor Slide |
| Presentation Time: | Sunday, November 5, 2000 10:15 AM-10:30 AM |
| Location: | Room 273 |
| Keywords: | EYE MOVEMENT, CONVERGENCE, VESTIBULAR, OCULOMOTOR |
Paths of rectus EOMs are constrained by connective tissue pulleys that serve as functional origins and determine EOM pulling directions. Magnetic resonance imaging (MRI) of human EOMs in secondary gaze positions indicates that pulley locations are consistent with the requirement of a linear oculomotor plant (Quaia & Optican, 1998) appearing commutative to its neural controller. In oculocentric coordinates, the distance between the pulley and globe center must equal the distance between globe center and EOM insertion. We have shown that the orbital layer of each EOM inserts on and translates the pulley while only the global layer rotates the eye (Demer et al 2000). MRI in humans was correlated with a geometrical model of EOM actions to show that active control of pulley position by the orbital layer can maintain geometry required by a linear oculomotor plant in tertiary gaze by posterior pulley displacement during EOM contraction. If EOM orbital layers can contract independently of global layers, then pulleys could shift independently of horizontal and vertical eye position. Additional posterior displacement of pulleys could account for observed violations of Listing’s law during the vestibulo-ocular reflex (VOR). Small pulley shifts can account for the temporal rotation of Listing’s plane during convergence. Torsion during VOR cancellation in secondary gaze positions can be explained by rectus pulley translation by orbital layers despite absence of oculorotatory innervation to the global layers of the EOMs. Independent control of pulleys offers the oculomotor system additional degrees of freedom and may account for seemingly paradoxical behavior recently observed in EOM motoneurons.
Supported by EY08313 & RPB
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2000 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2000. Online.
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