Motor Sequence Learning in Mild Cognitive Impairment and Alzheimer’s Disease and its Relationship to Biomarkers

Abstract

AbstractBackgroundWhile mild cognitive impairment (MCI) and Alzheimer’s disease (AD) are primarily associated with cognitive impairments, studies have also demonstrated that individuals may experience motor impairments that can precede cognitive symptoms by several years. Here, we examine potential differences in motor sequence learning abilities in individuals with MCI and AD compared to cognitively normal individuals (CNI). Moreover, we investigate whether motor sequence learning impairments could be an early behavioral biomarker. To that end, we evaluated associations between motor learning ability and existing AD biomarkers.MethodTo date, 26 individuals with AD, 27 with MCI, and 47 CNI performed a serial reaction time task that allowed us to assess the amount of sequence‐specific learning at the end of the task and the rate of such learning across the task. Additionally, participants underwent APOE genotyping to determine the presence of e4 alleles, amyloid PET imaging to quantify amyloid deposition, and structural MRI scanning to obtain hippocampal volume.ResultWhile motor responses of individuals with AD and MCI were generally slower than those of CNI, motor sequence learning occurred regardless of cognitive status and did not significantly differ among the three groups. Results of correlational analyses showed no significant associations between motor learning scores and AD biomarkers.ConclusionOur findings suggest that motor sequence learning abilities are relatively preserved in MCI and AD, which could have implications for the design of rehabilitation programs. However, its observed independence of existing biomarkers indicates that sequence learning may not be suitable as an early disease maker. Our ongoing work focuses on measuring general motor proficiency via a broad assessment spanning multiple motor domains, and evaluating whether such proficiency can serve as a predictor of disease status and progression.