Neuroscience 2001 Abstract
| Presentation Number: | 784.1 |
|---|---|
| Abstract Title: | MECHANICAL INTERACTIONS OF OBLIQUE EXTRAOCULAR MUSCLES (EOMs) WITH ACTIVELY CONTROLLED RECTUS PULLEYS MAINTAIN KINEMATICS OF LINEAR OCULOMOTOR PLANT. |
| Authors: |
Demer, J. L.*1,2
1Jules Stein Eye Inst, Univ California Med Sch, Los Angeles, CA 2Dept. of Neurology, Univ California Med Sch, Los Angeles, CA |
| Primary Theme and Topics |
Motor Systems - Oculomotor -- Head and eye movement |
| Secondary Theme and Topics | Motor Systems<br />- Oculomotor<br />-- Saccadic eye movement |
| Session: |
784. Oculomotor: head and eye movements II Slide |
| Presentation Time: | Wednesday, November 14, 2001 1:00 PM-1:15 PM |
| Location: | Room 7B |
| Keywords: | EYE MOVEMENT, MONKEY, MRI, Listing's Law |
The active pulley hypothesis proposes that the orbital layers (OLs) of rectus EOMs translate their connective tissue pulleys, while the global layers (GLs) rotate the eye. Rectus pulleys are actively controlled so that EOM velocity vectors shift by half the change in eye orientation, implementing a linear ocular motor plant. To evaluate the oblique EOM contribution, magnetic resonance imaging (MRI) of EOM paths was performed in humans, and correlated with histologic examination of 9 human (ages 0 – 93 yrs) and 8 monkey (rhesus, fascicularis, nemestrina, cebus) orbits. In all species, the inferior oblique (IO) muscle OL inserted on its collagenous pulley that was contiguous with the inferior rectus (IR) pulley, and on the lateral rectus (LR) pulley. This forces the IO to be coplanar with the IR and LR pulleys, and permits the contracting IO to displace both the IR and LR pulleys as verified by MRI. MRI shows IR contraction to displace the IO pulley by half the travel of the IR insertion. Mechanical coupling between the LR and SR pulleys completes a network accounting for MRI observation of rotation of the rectus pulley array around the gaze line during oblique EOM activation. Coupling of the IO to the actively-controlled IR and LR pulleys forces the IO velocity vector to be perpendicular to the rectus EOM vectors that in turn shift by half the change in eye orientation (Listing’s Law). The torsional action of the IO OL also translates the SR, LR, and IR pulleys. These findings extend the active pulley hypothesis to the oblique EOMs, and simplify the neural operations required to control eye movements.
Supported by EY08313 & RPB
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2001 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2001. Online.
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