[Impairments in initiation and execution of a visually-guided movement in baboon during cooling or after lesion of the internal pallidal segment (author's transl)]

Abstract

In the present experiment, the participation of the internal part of the globus pallidus (GP) in the initiation and the execution of a pointing movement was investigated in four baboons (Papio papio). The effects of GP exclusion on the response latency, the movement execution time and the pointing accuracy were analyzed. Two different methods were used to exclude the GP. In two cases, cryogenic blockade was induced using a chronic cryoprobe, implanted contralaterally to the operant hand. Two other animals underwent a partial electrolytic destruction of the GP, contralateral to the active hand. The effects of GP exclusion on reaction times, movement times and pointing accuracy were compared for movements with variable amplitudes and directions. For all animals, the GP exclusion resulted in a decrease in reaction time, but an increase in movement time and spatial error. None of these modifications was increased by variations in the biomechanic characteristics of the movement. These data show that the GP, in baboons, is concerned with: (a) the initiation of a pointing movement (without playing a critical role in the encoding of amplitude and direction parameters); and (b) the execution of this movement. The possible involvement of the GP in sensory-motor integration, postural adjustments and muscular synergy is discussed.