SACCADIC EYE MOVEMENT STUDIES

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The ultimate goal of our work is to understand how the brain functions. We concentrate on the output, or motor portions of brain function, using the oculomotor system as a model. Our recent studies of saccadic eye movements (the quick, step-like scanning eye movements we use to "look at" our visual world) have revealed new details about how saccades are programmed by the neural saccade generator. Specifically, we showed that the nucleus prepositus hypoglossi (nph) and the interstitial nucleus of Cajal cannot provide an internal control signal (local feedback) that specifies the correct saccade size. The neural integrator is an hypothesized nucleus that converts velocity-coded commands into eye-position discharge and thus integrates the signals in a mathematical sense. We also showed that the nph (the putative neural integrator) produces the oculomotor command signals to produce steady gaze at eccentric eye positions but cannot be used to supply eye-position or eye-velocity feedback to control saccade trajectory. Thus, current models must be revised to account for our recent results. These studies are basic to the differential neurological diagnosis based on eye-movement deficits now commonly used as well as to our understanding of oculomotor processes. In addition, they serve as a platform for studies of more complex aspects of central nervous system function, such as the interaction between motor systems (e.g., eye and head during orientation) or sensory and motor systems (e.g., the visual and oculomotor systems) as well as more abstract functions such as attention and memory.