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Different analyses of neuronal activity in primate models of Parkinson's disease (PD) have resulted in two different views on the effects of dopamine depletion. The first is based on the higher firing rate and bursty firing pattern, and assumes that dopamine depletion results in a hyperactivity of basal ganglia (BG) output structures. The second is based on the less-specific responses to passive joint manipulation and the excessive correlations between neuronal discharges, and assumes that dopamine depletion results in a loss of functional segregation in cortico-BG circuits. The aim of the present study was to test out the predictions of these two different views on thalamic neuronal activity. Three male vervet monkeys (Cercopithecus aethiops) were progressively intoxicated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Neuronal activities were characterized using standard analyses (firing rates and …