ENCODING MOVEMENT KINEMATICS IN THE PREMOTOR CORTEX

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Understanding the role of the central nervous system in the normal and abnormal motor behavior will require deciphering what parameters of movement are represented and where. Psychophysical observations support the hypothesis that reaching movements are planned and/or executed using a kinematic framework. Kinematically the direction, distance, velocity and accuracy of a movement are crucial components to positioning the arm in space. While neuronal correlates of movement direction have been studied and described in several cerebral cortical areas, the central representation of other arm movement parameters has received less attention. This proposal will evaluate five issues focused on the encoding of kinematic parameters in the discharge of primate premotor neurons. Emphasis is placed on determining the contributions and relationships between distance, direction, velocity and spatial accuracy in two and three dimensional arm reaching tasks. In the first Specific Aim the dependence of the activity of premotor neurons on the spatial accuracy of a movement will be evaluated. In the second Specific Aim a two dimensional tracking task will be used to dissect out relative importance and interactions between velocity, distance and movement time to the discharge of premotor cortical cells. In the third Specific Aim the neuronal correlates of movement amplitude will be studied in a three dimensional reaching task. In the fourth Specific Aim we propose to systematically alter the visual feedback, introducing errors into the movement. Using this complex, visually guided task, it will be determined whether the encoding of distance and direction remains invariant and whether the visuomotor "errors" are encoded in these cells' discharge. Lastly, in the fifth Specific Aim the premotor cortex has been hypothesized to play a role in learning the arbitrary associations that couple a movement to a stimulus. Using a learning paradigm which requires the scaling of movement kinematics due to a feedback change, we propose to study how adaptation of movement direction and distance is encoded at the single cell level. Overall, these studies will better define the role the premotor cortex plays in motor behavior.