Brain Advance Access published online on February 7, 2008
Brain, doi:10.1093/brain/awn011
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Focal basal ganglia lesions are associated with impairments in reward-based reversal learning
1Department of Neuropsychology, Institute of Cognitive Neuroscience, Ruhr-University Bochum and 2Department of Neurology, Klinikum Dortmund, Germany
Correspondence to:
Correspondence to: Dr Christian Bellebaum, Institute of Cognitive Neuroscience, Department of Neuropsychology, Ruhr-University of Bochum, Universitaetsstraße 150, D-44780 Bochum, Germany E-mail: christian.bellebaum{at}rub.de
The basal ganglia (BG) are thought to play a key role in learning from feedback, with mesencephalic dopamine neurons coding errors in reward prediction, thereby mediating information processing in the BG and the prefrontal cortex. In the present study, reward-based learning was assessed in patients with focal BG lesions, by studying outcome-based acquisition and reversal of stimulus–stimulus associations with different reward magnitudes in two probabilistic learning tasks. Eleven patients with selective BG lesions (three females) and 18 healthy control subjects (six females) participated in this study. Two cognitive transfer tasks provided a measure of declarative learning strategy application. On the group level, BG patients showed deficits in reversal learning, with dorsal striatum lesion patients being most severely affected. While basic mechanisms of learning from feedback such as the processing of different reward magnitudes appeared to be intact, patients needed more trials than controls to learn a second reward-based task, suggesting reduced carry-over effects in learning. A patient with a bilateral BG lesion showed better performance than controls on most learning tasks, applying a compensatory declarative learning strategy. The results are discussed in terms of the implication of different BG subregions in different aspects of learning from feedback.
Key Words: reward; basal ganglia; striatum; learning; reversal
Abbreviations: BA, basal ganglia; DA, dopamine; MRI, magnetic resonance imaging; MTL, medial temporal lobe; Put, putamen; RT, reaction time; SD, standard deviation; TIA, transient ischaemic attack
Received September 10, 2007. Revised January 8, 2008. Accepted January 10, 2008.
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