Specificity of the memory deficits associated with basal ganglia dysfunction

Recent studies comparing the explicit and implicit memory disorders of Huntington's disease (HD) and Alzheimer's disease (AD) patients have yielded new insights into the specificity of the memory disorders associated with basal ganglia dysfunction. Patients with HD have severe deficiencies in retrieving information from either episodic or semantic explicit memory. This retrieval deficit is not confounded by impairments in storage, rapid forgetting, intrusion errors and a deterioration of the structure of semantic knowledge. While HD patients perform normally on implicit memory tasks involving lexical, semantic and pictorial priming, they are impaired on implicit tests which require the initiation and/or modification of central motor programs. It is concluded that the basal ganglia play a specific but important role in memory although the processes they mediate are different from those dependent on the integrity of the hippocampus and diencephalon.