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. 1995 Jan 1;15(1):928–941. doi: 10.1523/JNEUROSCI.15-01-00928.1995

Eye movements in monkeys with local dopamine depletion in the caudate nucleus. II. Deficits in voluntary saccades

A Kori 1, N Miyashita 1, M Kato 1, O Hikosaka 1, S Usui 1, M Matsumura 1
PMCID: PMC6578280  PMID: 7823190

Abstract

Unilateral infusion of MPTP into the monkey caudate nucleus produced deficits in task-specific saccades, in addition to the deficits in spontaneous eye movements (preceding article). We trained three monkeys to perform two kinds of saccade tasks: (1) saccade task for eliciting visually guided saccades and (2) delayed saccade task for eliciting memory-guided saccades. After the MPTP infusion, dopaminergic function, estimated by tyrosine hydroxylase (TH) immunoreactivity, was shown to be decreased locally around the infusion site at the head-body junction of the caudate. We found that the deficits were prominent in the saccades directed to the side contralateral to the infusion (contralateral saccades). Memory-guided saccades were sometimes misdirected to the ipsilateral side even when the cue stimulus was presented on the contralateral side. Among the parameters of saccades, a selective change was found in the saccade latency: the latency was prolonged consistently in contralateral memory-guided saccades. The amplitude and velocity of saccades decreased in contralateral saccades, either memory guided or visually guided. The duration of saccades tended to increase in visually-guided saccades and memory-guided saccades, in both directions. Only one monkey, in which the decrease in TH activity included a large part of the putamen and the head of the caudate, showed prolongation of manual reaction time for lever release.


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