Background Huntington's disease (HD) is associated with progressive cognitive impairments.

Aims The aim of this ongoing study was to examine verbal episodic learning and memory in preclinical HD.

Methods Participants were recruited from the predictive testing program for HD at Karolinska University Hospital, Sweden. HD mutation carriers who were diagnosed with manifest HD within 9 years of cognitive assessment (HD ≤9 years, n=10) were compared with carriers that were not diagnosed within 9 years (HD >9 years, n=10) and non-carriers (n=38). Claeson–Dahl Learning and Retention Test (CD) and Fuld Object Memory Evaluation (FOME) were used to examine verbal episodic learning and memory. CD is an auditory, verbal learning and retention task consisting of a list of 10 words. FOME is a multimodal episodic learning and memory task using tactile, visual and verbal stimuli. Selective reminding of those objects not recalled is used during the five FOME recall trials.

Results The HD ≤9 years group scored significantly lower than non-carriers on the CD measures, Weighted Points (p=0.001) and Maximal Free Recall (p=0.012) and required more trials to learn the 10 words (p=0.01). They also had a higher incidence of perseverations (p=0.016) and confabulations (p=0.004). The HD >9 years group had more perseverative responses on CD than non-carriers (p=0.037). The HD ≤9 years scored lower than non-carriers on FOME measures Total Recall (p=0.009), Long Term Storage (p=0.016), Long Term Retrieval (p=0.029) and Effective Reminders (p=0.001), and lower than the HD >9 years on FOME Effective Reminders (p=0.006).

Conclusions The results indicate deficient verbal episodic learning in preclinical carriers of the HD allele. The results did not change with presentation modality (verbal in CD vs multimodal in FOME) or reminding paradigm (all 10 words in CD vs selective reminding in FOME). The increase in perseverative responses found for all carriers is consistent with deficits in mental flexibility early in preclinical HD.