Producing smoothly coordinated movements during performance of complex behaviors is an essential goal of the nervous system. To accomplish this, sensory information must be integrated continuously in order to construct a representation of objects in the world. This critical function requires the ability to distinguish between self-generated and object motion, to integrate diverse sensory information, and to plan and execute simultaneous motor behaviors. The interactions among neural structures that mediate selection and execution of coordinated movements, and the mechanisms that resolve the inherent conflict between stabilizing reflexes and motor commands are critical issues in understanding the neural control of coordinated action. The neural control of coordinated eye-head movements is an experimental system that has provided significant insights into the neural mechanisms mediating visual orienting behaviors. Directing the line of sight (gaze) towards interesting objects enhances our perception of the object and provides a way to construct and maintain an internal model of the world. These changes in gaze direction are generally accomplished by coordinating the eyes and head, and provide an excellent model system for studying the neural control of orienting behaviors, the coordination of multiple body segments, spatial orientation and transformation of sensory information into motor commands. The goals of the proposed research are to elucidate the neural computations and mechanisms required for coordination within the context of visual orienting movements. We will record the activity of neurons in the brainstem during gaze shifts made when the head is free to move. We will determine the relationship between the activity of these cells and the metrics and/or kinematics of the gaze, eye and/or head movements, we will characterize the activity of cells in the nucleus reticularis gigantocellularis and identify their role in generation of head movements, and we will record activity simultaneously from cells in the superior colliculus (SC) and cells downstreamfrom the SC in an effort to reveal the underlying mechanisms that transform SC signals into the commands needed to move the eyes and head. These experiments will provide exciting and novel insight into the ways in which the nervous system converts sensory inputs into coordinated actions.
