K. Kurata et E. Hoshi, Reacquisition deficits in prism adaptation after muscimol microinjection into the ventral premotor cortex of monkeys, J NEUROPHYS, 81(4), 1999, pp. 1927-1938
A small amount of muscimol (1 mu l; concentration, 5 mu g/mu l) was injecte
d into the ventral and dorsal premotor cortex areas (PMv and PMd, respectiv
ely) of monkeys, which then were required to perform a visually guided reac
hing task. For the task, the monkeys were required to reach for a target so
on after it was presented on a screen. While performing the task, the monke
ys' eyes were covered with left 10 degrees, right 10 degrees, or no wedge p
risms, for a block of 50-100 trials. Without the prisms, the monkeys reache
d the targets accurately. When the prisms were placed, the monkeys initiall
y misreached the targets because the prisms displaced the Visual held. Befo
re the muscimol injection, the monkeys adapted to the prisms in 10-20 trial
s, judging from the horizontal distance between the target location and the
point where the monkey touched the screen. After muscimol injection into t
he PMv, the monkeys lost the ability to readapt and touched the screen clos
er to the location of the targets as seen through the prisms. This deficit
was observed at selective target locations, only when the targets were shif
ted contralaterally to the injected hemisphere. When muscimol was injected
into the PMd, no such deficits were observed. There were no changes in the
reaction and movement times induced by muscimol injections in either area.
The results suggest that the PMv plays an important role in motor learning,
specifically in recalibrating Visual and motor coordinates.