Neuroscience 2003 Abstract
| Presentation Number: | 391.17 |
|---|---|
| Abstract Title: | Functional anatomy of extraocular muscles (EOMs) during static torsional vestibulo-ocular reflex (VOR) revealed by magnetic resonance imaging (MRI). |
| Authors: |
Demer, J. L.*1,2
; Clark, R. A.1
1Jules Stein Eye Inst, David Gefffen Med. Sch. at UCLA, Los Angeles, CA 2Neurol., David Gefffen Med. Sch. at UCLA, Los Angeles, CA |
| Primary Theme and Topics |
Motor Systems - Oculomotor -- Physiology |
| Secondary Theme and Topics | Motor Systems<br />- Oculomotor<br />-- Anatomy |
| Session: |
391. Anatomy & Physiology Poster |
| Presentation Time: | Monday, November 10, 2003 8:00 AM-9:00 AM |
| Location: | Morial Convention Center - Hall F-I, Board # I6 |
| Keywords: | EYE MOVEMENT, KINEMATICS, OCULOMOTOR, VESTIBULAR |
While actively-controlled rectus pulleys explain Listing’s Law (L1) during visually-guided eye movements, it has been difficult to account for violations during the VOR. Tri-planar gadodiamide contrast MRI was obtained in 10 adult humans during central target fixation while positioned in the right (RD) and left (LD) lateral decubitus positions to evoke static ocular counter-rolling. EOM cross sections and paths were determined from area centroids. Paths were used to locate pulleys in 3-D. Correct head orientation was verified from MRI images. Significant (P < 0.01) binocular counter-rotational repositioning in the coronal plane averaging 4.1° (max 8.7°) from RD to LD was observed for inferior, medial, and superior rectus pulleys, with a trend for lateral rectus averaging 1.4°. Pulley array incyclorotation was associated with significant contractile thickening of the superior oblique (SO) and thinning of the inferior oblique (IO) muscles, while excyclorotation was associated with SO thinning and IO thickening. Rectus pulley configuration during the VOR, which changes the pulling directions of the rectus EOMs, is probably actively mediated by known insertions of the orbital layers of the oblique EOMs on rectus pulleys. The amount of pulley reconfiguration is comparable to ocular counter-rolling, suggesting coordinated kinematics of rectus pulleys and insertions that would simply offset Listing’s plane. Larger rectus pulley repositioning during the higher-gain dynamic torsional VOR could explain observed violations of L1.
Supported by EY08313 & RPB
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2003 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2003. Online.
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