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

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.

Saccadic latency distributions in Parkinson’s disease and the effects of l-dopa

“…The effect on reaction times seems to be dependent on the testing paradigm (simple 'reflexive' reaction time versus 'voluntary' or choice reaction time), and the dopaminergic tone, which in turn depends on the severity of PD, the dose of replacement therapy and the timing of subsequent testing. A dissociation between voluntary saccadic latency and manual reaction time has already been shown in the monkey following local depletion of dopamine in the caudate nucleus, albeit with prolongation of saccadic latency in this case (Kori et al 1995). Careful analysis of saccadic latencies and manual reaction times in humans in response to different testing paradigms will shed further light on the relationship between these variables and the role of dopamine in the decision process.…”

Nicotine and Behavioral Markers of Risk for Schizophrenia A Double-Blind, Placebo-Controlled, Cross-Over Study

“…Saccade amplitude increases following an oral dose of L-dopa (an indirect DA agonist) in patients with Parkinson's disease (Gibson et al 1987;Rascol et al 1989). In contrast, saccade amplitude decreases after DA depletion (Kori et al 1995) in monkeys; saccade amplitudes are also reduced in patients with degenerative diseases of the basal ganglia including Parkinson's disease (Straube et al 1998). Thus, saccade amplitude is sensitive to changes in nigrostriatal DA function (Rascol et al 1989) and may have been the neural substrate of the nicotine-related changes in amplitude observed in the current study.…”

Subcortical processes of motor response inhibition during a stop signal task

“…Earlier animal, clinical, and neuroimaging research has provided extensive evidence for a role of the caudate nucleus in cognitive-motor control. For instance, chemical lesion of the caudate head impaired monkey's ability to suppress a reflexive saccade to sudden visual onsets and to initiate a delayed saccade (Kori et al, 1995). Stroke patients with lesions in the caudate nucleus demonstrated prominent motor preserveration as demonstrated in a "star cancellation" task, a deficit that was independent of the extent of visual neglect (Nys et al, 2006).…”