Three of the main cortical inputs to the primary motor cortex (MI) are the premotor cortex (PM), the supplementary motor cortex (MII) and the transition zone between the motor and somatic sensory cortex, area 3a. These three cortical fields surround MI and, in this project, were differentiated from MI on the basis of neuronal responses to peripheral inputs, thresholds for evoking movements with intracortical electrical stimulation, the properties of single neurons during the performance of an operantly conditioned motor task, cytoarchitecture, and connectivity. In our most recent work, we have concentrated on one of these fields, PM, and an analysis of its neuronal activity during a variety of visually guided motor tasks. Each task was designed to elucidate the role of PM in the cerebral control of movement. We have tested the following hypotheses: (1) that PM guides movement to points in space, (2) that PM is involved in the sensory guidance of movement, (3) that it is especially important when such sensory guidance is of an abstract nature, (4) that PM plays a role in motor preparation, (5) that it functions in the determination of movement parameters, (6) that PM is especially important in controlling sequences of movement, and (7) that it reflects eye position, gaze position, postural muscle activity, visual fixation, attention, motivation, or arousal. Of these ideas, our results support the hypothesis that PM plays a role in the execution of visually guided movements, especially those guided by astract sensory cues, and the preparation for voluntary movements. These studies have provided new insight into the process termed preparatory set, which may underlie the ability of animals to make advantageous preparations for actions in the future. As such, it represents a higher brain function amenable to both quantitative and qualitative neurophysiological analysis.
Showing the most recent 10 out of 39 publications
