The role of the basal ganglia in learning and memory: neuropsychological studies

In recent years, a common approach to understanding how the basal ganglia contribute to learning and memory in humans has been to study the deficits that occur in patients with basal ganglia pathology, such as Parkinson's disease and Huntington's disease. Pharmacological manipulations in patients and in healthy volunteers have also been conducted to investigate the role of dopamine, a neurotransmitter that is crucial for normal striatal functioning. When combined with powerful functional neuroimaging methods such as positron emission tomography and functional magnetic resonance imaging, such studies can provide important new insights into striatal function and dysfunction in humans. In this review, we consider this broad literature in an attempt to define a specific role for the caudate nucleus in learning and memory, and in particular, how this role may differ from that of the putamen. We conclude that the caudate nucleus contributes to learning and memory through the excitation of correct action schemas and the selection of appropriate sub-goals based on an evaluation of action-outcomes; both processes that are fundamental to all tasks involve goal-directed action.