It is remarkable how well the oculomotor system is able to maintain precise alignment of the two eyes. If all eye movements were between distant targets and required equal movements in the two eyes the task would be relatively simple. However, naturally occurring eye movements are very often between targets that differ in viewing distance and eccentricity and so require a disconjugate component. Good binocular alignment may also be affected by development, disease, and injury. The proposed experiments examine the processes by which subsystems such as vergence, smooth pursuit, and saccades interact to produce the requisite changes in binocular alignment. For example, despite the claims of some investigators, it is still not certain whether all horizontal vergence movements are the result of control by the horizontal vergence system or if there is some capacity for disconjugate movements by the pursuit or saccade systems. Similarly, it is not clear whether the so-called disconjugate adaptation of saccades is really disconjugate adaptation of the saccadic pulse or step or is simply the addition of vergence movements onto conjugate saccades. We will address some common problems with the interpretation of prior experimentation in this area. The proposed experiments fall into three general categories: The first is a series of experiments that represents a continuation of our adaptation experiments on vertical vergence and examines the neural control of disconjugate smooth pursuit. The second will examine more closely the binocular control of saccades and the interaction of saccades with horizontal and vertical vergence movements. The third continues our exploration of the binocular control of eye movements during head tilt and the relationship between ocular counterroll and vertical skew. The results of these experiments should provide definitive answers to several longstanding questions concerning the coordination of binocular control.
Showing the most recent 10 out of 70 publications
