Journal of Neurophysiology, Vol 44, Issue 6 1139-1147, Copyright © 1980 by APS
Amplitude of responses to perturbation in primate sensorimotor cortex as a function of task
J. R. Wolpaw
1. Monkeys learned to maintain hand position against a range of background
forces. Short-latency responses to passive wrist extension or flexion were
recorded from units in areas 4, 3, 1, and 2. Response amplitude was studied
as a function of background force direction (extension or flexion). 2. For
40% of the precentral and postcentral responses, response amplitude
depended on constant force direction. For these dependent responses,
amplitude with background force in one direction averaged 2.8 times
amplitude with background force in the opposite direction. 3. Units for
which background activity varied with constant force direction were
designated task related. Dependent responses from area 4 task-related units
were usually larger when background activity was greater and when
background force direction matched the direction of the passive movement.
4. Dependent responses from area 4 task-related units occurred
significantly later than nondependent responses from the same units. 5.
Since most area 4 task-related activity was explicable as a result of
peripheral input via the same oligosynaptic path mediating area 4 responses
to passive movements (32), the present findings imply that area
4-task-related activity may result in large part from centrally mediated
change in the access of short-latency peripheral input to area 4 units. 6.
The dependence of responses from non-task-related area 4 units and from
non-task-related and task-related postcentral units showed no dominant
correlation with background activity or with background force direction.
Their dependence appeared to require no explanation other than a change in
peripheral input with change in background force direction.
