The long-term goal of this project is to elucidate the neural mechanisms which underlie both the processing of cognitive information and the learning of motor adaptations associated with spatial-motor behavior. Neurophysiological recordings of the activity of single neurons will be undertaken to achieve this goal in monkeys trained to perform multi-joint, multidirectional reaching movements of the arm during the performance of instructed-delay tasks. Physiological, anatomical and behavioral studies have shown that the frontal lobe is an important structure for the generation of (a) reaching behavior in extrapersonal space, (b) proper movement sequencing, and (c) the utilization of requisite information from memory and sensory systems for guided movements. This is a behavioral neurophysiology study of four major divisions of the frontal lobe of primates: the primary motor cortex (M1), dorsal premotor cortex (PMd), ventral premotor cortex (PMv) and supplementary motor area (SMA). Two paradigms involving the serial presentation of spatial information are used to investigate the relationship between neuronal activity in each cortical motor area and the processing of requisite visual-spatial information for reaching. In one, either a previously learned or novel movement sequence is prepared and executed by a monkey. This task will determine which specific attributes of spatial reaching are preprocessed and encoded in neuronal activity at the cortical level in signals either retrieved from memory or generated de novo and whether movement sequences are represented in neural signals as transformations between spatial representations of component movement segments, or, as complex vectorial representations, or as a generalized rule which describes the relationship between the first and second movement segments. In the second task, a robot arm with servo motors at the shoulder and elbow joints is used to rapidly change the mechanical environment of reaching movements and accordingly modify the sensorimotor experience of producing different reaching movements with the same starting and final arm positions. The robot arm will rapidly produce unfamiliar mechanical environments and simulate collisions between the arm and """"""""virtual"""""""" objects at specific locations along the movement trajectory. This design will allow the neural correlates of learned adaptations of spatial-motor behavior to be studied and will determine if this activity is localized to specific frontal cortical areas and evaluate the contribution of visual and somatosensory afferent information used in this conditional motor learning task.
