Impaired dimensional selection but intact use of reward feedback during visual discrimination learning in Parkinson's disease.

Full Abstract

It has been suggested that Parkinson's disease (PD) impairs the ability to learn on the basis of reward or reinforcing feedback i.e., by trial-and-error. In many learning tasks, particular 'dimensions' of stimulus information are relevant whilst others are irrelevant; therefore, efficient performance depends on identifying the dimensions of these 'compound' stimuli and selecting the relevant dimension for further processing. We investigated the ability of patients with PD, as well as patients with Huntington's disease and patients with frontal or temporal lobe lesions, to learn visual discriminations which required either a number of associations to be learned concurrently (the 'eight-pair' task) or the selection of information from compound stimuli (the 'five-dimension' task), both tasks being learned by trial-and-error. None of the basal ganglia disorder patient groups was impaired on the eight-pair task, militating against a crucial role for these brain structures in trial-and-error learning per se. Patients with mild, medicated PD, but not unmedicated PD patients, were impaired at identifying all five feature dimensions in the five-dimension task, implying dopaminergic 'overdosing' of the ability to analyse compound stimuli in terms of their component dimensions. Temporal lobe lesion patients performed similarly, suggesting that the temporal lobe may be the site of the medication overdose effect. Patients with severe, medicated PD were impaired at compound discrimination learning on the five-dimension task in the absence of an underlying impairment in identifying component stimulus dimensions; this pattern resembled that seen in Huntington's disease and frontal lobe lesion patients, implying that fronto-striatal circuitry is involved in the formation of rules based upon selected stimulus dimensions.

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Author information

Author/s: Swainson, R (R); SenGupta, D (D); Shetty, T (T); Watkins, L H A (LH); Summers, B A (BA); Sahakian, B J (BJ); Polkey, C E (CE); Barker, R A (RA); Robbins, T W (TW);

Affiliation: Department of Experimental Psychology, University of Cambridge, Cambridge, UK. rachel.swainson(-atsign-)nottingham.ac.uk

Grants: 076274/Z/04/Z (Agency:Wellcome Trust)

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Journal: Neuropsychologia (Neuropsychologia), published in England. (Language: eng)

Reference: 2006-; vol 44 (issue 8) : pp 1290-304

Dates: Created 2006/05/12; Completed 2006/08/04; Revised 2007/08/13;

PMID: 16529779, status: MEDLINE (last retrieval date: 12/26/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Analysis of Variance
Brain - pathology
Discrimination (Psychology) - physiology
Discrimination Learning - physiology
Feedback, Psychological - physiology
Female
Humans
Huntington Disease - pathology; physiopathology
Magnetic Resonance Imaging - methods

Magnetic Resonance Imaging - methods
Male
Middle Aged
Neuropsychological Tests - statistics & numerical data
Parkinson Disease - pathology; physiopathology
Photic Stimulation - methods
Recognition (Psychology) - physiology
Reward
Statistics, Nonparametric
Visual Perception - physiology

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