D. Jaeger et al., NEURONAL-ACTIVITY IN THE STRIATUM AND PALLIDUM OF PRIMATES RELATED TOTHE EXECUTION OF EXTERNALLY CUED REACHING MOVEMENTS, Brain research, 694(1-2), 1995, pp. 111-127
We studied changes in basal ganglia neuronal activity associated with
reaching movements of the arm in two monkeys. Data were obtained from
427 single neuronal units in putamen, 199 in caudate nucleus, and 216
in globus pallidus with multiwire electrodes allowing simultaneous rec
ordings from multiple neurons. In all structures, changes in activity
related to movement occurred most often after the onset of EMG: 43% of
tested neurons in the putamen, 32% in the caudate nucleus, and 38% in
the globus pallidus. Less frequently, changes began before EMG activa
tion: 20% of neurons in the putamen, 19% in caudate nucleus, and 17% i
n globus pallidus. In general, these changes in neuronal activity last
ed longer than EMG activity associated with reaching. The proportions
of neurons activated were significantly larger in the putamen than the
caudate nucleus. In the pallidum, the proportions were not statistica
lly different from either the putamen or caudate nucleus, and no signi
ficant difference was found between the internal and external pallidal
segments. Significant selectivity for movements to different targets
was observed in 36% of neurons in the putamen, 28% in the caudate nucl
eus and 9% in the globus pallidus. The lower proportion in the globus
pallidus compared to the striatum was significant (P < 0.002). Cluster
s of activated neurons were found in the striatum, however, the timing
of changes was often different for individual neurons in these cluste
rs. A cross-correlation analysis of the activity of neurons in the clu
sters revealed no evidence of common inputs, suggesting that striatal
neurons in close proximity with neurons showing similar changes in act
ivity are driven by different populations of neurons. In the putamen,
the anatomical locations of neurons with changes in activity related t
o movement execution were on average significantly more posterior and
lateral than neurons with changes related to the preparation of moveme
nt described earlier [31]. These findings support the view that the pu
tamen and the caudate nucleus contain distinct functional areas. The p
resent studies show that most anatomical regions in both the striatum
and pallidum participate in the control of executing reaching movement
s.