Associative encoding and retrieval in Alzheimer's and Huntington's disease

The associative encoding and retrieval abilities of patients with dementia of the Alzheimer type (DAT) and patients with Huntington's disease (HD) were investigated using an encoding specificity paradigm. When compared to age- and education-matched intact control subjects, both patient groups were severely (and equally) impaired on overall memory for word lists. However, the HD and DAT patients showed differential improvement in recall performance with the introduction of associated cues during stimulus presentation and recall. Although the HD patients, like intact subjects, were able to benefit from semantic retrieval cues (strong and weak) which were present during input, the performance of the patients with DAT improved only with the introduction of strong cues at output, regardless of whether the cues were present or absent during initial presentation. These findings suggest that patients with DAT failed to encode the semantic relationship between the to-be-recalled and cue words and simply generated free associations to the cue words during retrieval. Similarities between the performances of the patients with DAT and alcoholic Korsakoff patients are noted and discussed with regard to the neuropathological basis of the disorders.