All ETDs from UAB

Advisory Committee Chair

Claudio Busettini

Advisory Committee Members

Roderick J Fullard

Paul D Gamlin

Timothy J Gawne

Kristina M Visscher

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) School of Optometry

Abstract

A long standing debate regarding the neural organization of oculomotor control began in the late 1800's with Hering and von Helmholtz proposing two opposing ideologies. Von Helmholtz proposed a monocular structure of the oculomotor circuitry in which each eye receives separate motor commands. Hering offered his law of equal innervation, which states that all eye movements are the sum of binocular vergence and conjugate commands. As a test of Hering's binocular proposal, this project compared the behavior of midbrain vergence cells during: 1) saccade-free stepwise transfers of gaze in depth; 2) combined saccade-vergence eye movements; 3) pure vergence tracking, and 4) smooth tracking in depth along oblique directions in space. Hering's law of equal innervation requires that vergence cell firing would remain consistent whether the movement is a pure vergence movement or a combination of vergence and conjugate commands. For this project, the perturbing conjugate commands of the first experiment were saccades, and smooth pursuit was introduced in the second experiment. Evidence for the majority of midbrain vergence cells to encode only part of the vergence response during these interactions directly challenges Hering's law of equal innervation.

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