Primate motor cortex and free arm movements to visual targets in three- dimensional space. I. Relations between single cell discharge and direction of movement

• Published in: The Journal of neuroscience Vol. 8; no. 8; pp. 2913 - 2927
• Main Authors: Schwartz, AB, Kettner, RE, Georgopoulos, AP
• Format: Journal Article
• Language: English
• Published: Washington, DC Soc Neuroscience 01.08.1988; Society for Neuroscience
• Subjects: Animals; Arm; Biological and medical sciences; Carpus, Animal; Electromyography; Fundamental and applied biological sciences. Psychology; Macaca - physiology; Macaca mulatta - physiology; Male; Models, Neurological; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor Cortex - cytology; Motor Cortex - physiology; Movement; Neurons - physiology; Psychomotor Performance - physiology; Reaction Time; Regression Analysis; Space life sciences; Vertebrates: nervous system and sense organs; Brain; Monkey; Central nervous system; Electrophysiology; Goal directed movement; Three dimensional space; Visuomotor tracking; Vertebrata; Target; Unit response; Mammalia; Motor cortex; Body movement; Primates; Arm; Stimulus direction
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.08-08-02913.1988

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.