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, 29 (8), 1237-46

Striatal Dopamine Transporters Correlate With Simple Reaction Time in Elderly Subjects

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Striatal Dopamine Transporters Correlate With Simple Reaction Time in Elderly Subjects

Christopher H van Dyck et al. Neurobiol Aging.

Abstract

The decline in motor performance that accompanies advanced age has unclear neurobiological substrates but may relate, in part, to degeneration of the nigrostriatal dopamine system. This research tested the hypothesis that striatal dopamine transporter (DAT) availability in healthy elderly individuals was related to measures of motor performance. Thirty-six healthy volunteers (18 male, 18 female) who ranged in age from 68 to 88 (75.4+/-4.9 years) received a neuropsychological evaluation that included two primary motor measures (tested with dominant hand): (1) simple reaction time (SRT); and (2) finger tapping (FT). Subjects underwent SPECT scanning with [(123)I]2beta-carbomethoxy-3beta-(4-iodophenyl)tropane ([(123)I]beta-CIT) for measurement of striatal DAT availability. A ratio of specific to nondisplaceable brain uptake (i.e., radical V3 =[striatal-occipital]/occipital), a measure proportional to the binding potential (B(max)/K(D)), was derived. SRT was significantly correlated with striatal DAT availability with or without controlling for the contribution of age. However, contrary to hypothesis, FT was not correlated with striatal DAT availability. Comparison measures, including episodic memory and general intelligence, were also unrelated to striatal DAT availability. These results demonstrate that a loss of nigrostriatal dopaminergic function likely contributes to slowing of reaction speed with advancing age.

Figures

FIGURE 1
FIGURE 1
Simple Reaction Time (SRT) versus striatal dopamine transporter (DAT) availability (V3″) as measured by [123I]ß-CIT and SPECT in healthy elderly subjects (N=36). SRT represents the median speed (in ms) with which subjects responded to a visual stimulus (presented on a computer monitor) by pressing a single microswitch key with the index finger of the dominant hand. SRT showed a significant inverse correlation with V3″ either with (P=.016) or without (P=.017) controlling for age.
FIGURE 2
FIGURE 2
Finger Tapping (FT) versus striatal dopamine transporter (DAT) availability (V3″) as measured by [123I]ß-CIT and SPECT in healthy elderly subjects (N=36). FT represents the number of key presses per 10 s with the index finger of the dominant hand, averaged across five trials. FT was not significantly correlated with V3″.

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