The long-term goal of this research program is to produce quantitative neurophysiological data in monkey and comprehensive models based on this data that can constitute the basis for a deeper understanding of oculomotor disorders in man. The focus of the neurophysiological investigations during the forthcoming project period will be the organization of dynamic control in the saccadic eye movement system.
Specific aims i nclude: (1) Testing of the hypothesis that the superior colliculus provides the dynamic motor error signal that controls saccadic trajectory. This hypothesis will be tested by examining collucular discharge during saccades with highly varied velocity profiles produced by intrasaccadic electrical stimulation of the frontal eye fields or the brainstem omnipauser region or by high speed moving visual targets. (2) Exploration of the hypothesis that the collucular projection circuit composed of nucleus reticularis tegmenti pontis/fastigial nucleus provides an additional corrective control signal to that output by the colliculus. Neurons in these two structures will be recorded during saccades with different initial positions and for saccades made to moving visual stimuli--both examples of the type of saccade which requires an additional dynamic correction to that provided by the colliculus. (3) Investigation of a possible site of the neuronal mechanisms underlying saccadic adaptative gain control by making chemical lesions in the nucleus reticularis and in the fastigial nucleus. Two new development sin oculomotor research form the unifying principle around which all the experiments are planned: (1) The claim that dynamic control of saccadic trajectory is carried out by neurons in the colliculus and not the brain stem as previously supposed. (2) The suggestion that the colliculus may output a control signal to the brainstem premotor circuits which only specifies the metrics of the desired change in gaze. This signal must be refined by subsequent neural circuits to provide the necessary corrections to actually control individual ocular muscles under a variety of conditions. Examples of these varied conditions include saccades from different initial orbital positions, saccades to moving targets, and saccades made after adaptation to alterations in orbital mechanics.
