The Retrieval Deficit Memory Profile in Huntington’s Disease: Reexamining Old Heuristics and Exploring New Ones

Rationale: Memory dysfunction in Huntington’s disease (HD) has been characterized as a primary retrieval deficit. Evidence for this conceptualization emerged from findings that individuals with HD demonstrate disproportionate improvement on recognition versus free recall. However, findings are mixed regarding memory performance in HD, with some studies supporting the recall/recognition discrepancy and others demonstrating similar levels of impairment in these processes. The present study aimed to improve understanding of memory in HD by examining two possible explanations for the inconsistent findings: 1) different operational definitions of the retrieval deficit profile may result in mixed findings regarding the nature of memory dysfunction in HD, and 2) neurocognitive mechanisms underlying memory dysfunction in HD may vary as a function of the level of global cognitive impairment. Design: The present study used archival data from the California Verbal Learning Test-II. The first aim included 27 individuals with Alzheimer’s disease (AD), 39 individuals with HD, and 70 healthy adults (HA). Various contrasts of recall and recognition were used in a discriminant function analysis to determine if one was superior in discriminating between groups. The second aim included 72 individuals with HD. Using a previous discriminant function algorithm, individuals were classified as having one of three memory profiles: normal, encoding deficit, or retrieval deficit. Logistic regression analysis was conducted to determine if overall cognitive impairment, measured by the Dementia Rating Scale, predicted memory profile. Results: In the first aim, the contrast of Total Recognition Discriminability - Trial 5 Recall was superior to other contrasts in distinguishing between groups and resulted in a correct classification rate of 77.6%. In the second aim, memory profiles of HD patients were classified as: normal profile = 7%, encoding deficit = 33%, and retrieval deficit = 60%. For individuals classified with memory impairment, global cognitive impairment did not predict memory profile. Relevance: Refining characterization of memory dysfunction in HD may help resolve inconsistencies in the literature and enhance understanding of the cognitive sequelae of this neurodegenerative disease. Improved understanding of the course of memory impairment in HD may inform interventions to target specific neurocognitive mechanisms at different stages of the disease