Fig. 11.3.

Dissociations can be demonstrated in non-focal lesion conditions. Here, explicit and implicit memory scores in individuals with Korsakoff’s syndrome (KS) and others with Huntington’s disease (HD) are compared with a control group and between themselves. Studies have generally demonstrated that explicit memory processes are more affected than implicit memory processes in KS, whereas the opposite pattern, greater impairment in implicit than explicit memory processes, has been demonstrated in conditions with primary subcortical dysfunction such as HD. This pattern of deficits can be visually compared with a group of controls (left and middle graphs) or can be shown as a cross-over interaction between the two neurologic groups (right graph). The differences in mnemonic processes observed in these conditions are presumably caused by the different neuroanatomic regions affected in these disorders: frontolimbic deficits in KS and basal ganglia dysfunction in HD.