Akinesia after Globus Pallidus Lesion in Monkeys Performing Reaction time Tasks Involving Speed or Accuracy Constraints
Experimental investigations have established that the globus pallidus (GP) plays a key role in the control of the motor execution phase of movement (Trouche et al., 1979; Beaubaton et al. 1981; Horak and Anderson, 1984; Mink and Thach, 1991c). Moreover, the existence of strong afferent inputs to the GP from the striatum, which is involved in movement initiation, suggests that the GP may be engaged in the neural processes underlying the initiation phase of movement. Some electrophysiological data seem to support this idea: a change in the neuronal discharge was observed prior to the onset of electromyographic activity in the cat (Neafsey et al., 1978) and the monkey (Nambu et al., 1990). However, data from studies involving experimental lesions in monkeys, showing that after GP lesion no increase in the movement latency occurred in a reaching task (Horak and Anderson, 1984) or in a tracking task (Mink and Thach, 1991c), are not compatible with the idea that the GP may contribute to the control of motor initiation: the role of the GP in motor initiation is still a matter of controversy. These discrepancies may hower be due to differences between the experimental paradigms used by the various authors. For this reason, we decided to study the effects of GP lesion on movement performance in various reaction time tasks. Here we present data obtained in two reaction time tasks which showed that the GP was involved in the control of motor initiation: a simple RT task with a speed constraint and a choice RT task with an accuracy constraint.
KeywordsGlobus Pallidus Reaction Time Task Large Amplitude Movement Accuracy Constraint Pallidal Neuron
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