title: Primate motor cortex and free arm movements to visual targets in three-dimensional space. I. Relations between single cell discharge and direction of movement.
abstract: We describe the relations between the neuronal activity in primate motor cortex and the direction of arm movement in three-dimensional (3-D) space. The electrical signs of discharge of 568 cells were recorded while monkeys made movements of equal amplitude from the same starting position to 8 visual targets in a reaction time task. The layout of the targets in 3-D space was such that the direction of the movement ranged over the whole 3-D directional continuum in approximately equal angular intervals. We found that the discharge rate of 475/568 (83.6%) cells varied in an orderly fashion with the direction of movement: discharge rate was highest with movements in a certain direction (the cell's "preferred direction") and decreased progressively with movements in other directions, as a function of the cosine of the angle formed by the direction of the movement and the cell's preferred direction. The preferred directions of different cells were distributed throughout 3-D space. These findings generalize to 3-D space previous results obtained in 2-D space (Georgopoulos et al., 1982) and suggest that the motor cortex is a nodal point in the construction of patterns of output signals specifying the direction of arm movement in extrapersonal space.
authors.affiliation: Philip Bard Laboratories of Neurophysiology, Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205.
authors.forename: A B
authors.initials: AB
authors.lastname: Schwartz
authors.forename: R E
authors.initials: RE
authors.lastname: Kettner
authors.forename: A P
authors.initials: AP
authors.lastname: Georgopoulos
mesh_terms: D000818:Animals; D001132:Arm; D002350:Carpus, Animal; D004576:Electromyography; D008251:Macaca / Q000502:physiology*; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D009068:Movement; D009474:Neurons / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time; D012044:Regression Analysis