Authors:

OWEN, A.M., Doyon, J., Dagher, A., Sadikot, A., & Evans, A.C.

Reference:

Year of publication:

1998

CBU number:

3656

Abstract:

Traditionally, the basal ganglia have been associated with motor processes, although recent evidence suggests that they may also subserve parallel cognitive functions. For example, patients with Parkinson’s disease (PD), a neurodegenerative disorder characterised by severe dopamine depletion in the striatum, exhibit a progressive pattern of neuropsychological impairment, which, in its earliest stages, resembles that seen after damage to the frontal lobes. In this study we examined the effects of striatal dopamine depletion on cortical and subcortical blood flow changes during two tasks known to involve fronto-striatal circuitry. Regional cerebral blood flow was measured in six patients with moderate Parkinson's disease and in six age-matched controls while subjects performed easy and difficult versions of a modified Tower of London planning task and a mnemonic variant of this task that required short-term retention and reproduction of problem solutions, as well as a control condition that involved identical visual stimuli and motor responses. The results suggest that in PD, striatal dopamine depletion disrupts the normal pattern of basal ganglia outflow and consequently, affects the expression of frontal-lobe functions by interrupting normal transmission of information through frontostriatal circuitry.