Subtle visuomotor difficulties in preclinical Alzheimer's disease

BackgroundIndividuals with preclinical Alzheimer's disease (Pre-AD) present nonimpaired cognition, as measured by standard neuropsychological tests. However, detecting subtle difficulties in cognitive functions may be necessary for an early diagnosis and intervention. ObjectivesA new computer-based visuomotor coordination task (VMC) was developed to investigate the possible presence of early visuomotor difficulties in Pre-AD individuals. Associations between VMC task performance and AD biomarkers were studied. The influence of ApoE status on participants' performance was addressed, as well as the relationship between performance and subjective cognitive decline (SCD). MethodsSixty-six cognitively normal (CN) elders (19 Pre-AD and 47 control participants [CTR]) and 15 patients with AD performed the VMC task, which consisted in executing visually guided goal-directed movements that required the coordination of the visual and motor systems. All participants underwent ApoE analysis and lumbar puncture. CN participants also completed an extensive standard neuropsychological battery. ResultsDespite presenting normal cognition in standard tests, Pre-AD participants exhibited higher response times (RTs) to complete the VMC task than CTR (p<.01). Besides, patients with AD showed higher RTs than CTR (p<.001) and Pre-AD (p<.05), and more errors than CTR (p<.005). RTs in ApoE4 carriers were higher than that observed in ApoE4 noncarriers (p<.01). In CN individuals, RTs were related to amyloid -protein 42 (AB42) biomarker (p<.01) and informant-rated SCD (p<.01). ConclusionsThe VMC task is able to discriminate Pre-AD from CTR individuals. Moreover, VMC results are associated with AB42 levels in CN individuals, suggesting that visuomotor dysfunction may be a sensitive marker of Pre-AD.