Determining the Contribution of Implicit and Explicit Motor Learning in Older Adults with and without Mild Cognitive Impairment

• Madison Munoz, Exercise Science, University of Delaware

• Susanne M Morton, Physical Therapy, University of Delaware

Motor learning, the process by which movement skills are acquired and refined, occurs through a combination of explicit and implicit mechanisms. Explicit learning is consciously controlled and requires attention and awareness, whereas implicit learning occurs subconsciously, relying on more automatic processes. Our previous work in individuals with mild cognitive impairment (MCI) demonstrated that cognitive impairment hinders motor learning tasks that require use of a conscious strategy. However, the contributions of explicit and implicit learning were not examined. Therefore, here, we examined  these contributions and compared them between healthy older adults and older adults with MCI. We hypothesized that only the explicit contribution to learning, and not implicit, would be impaired in individuals with MCI. Twenty-six healthy older adults and twenty-three older adults with MCI learned an asymmetric walking pattern either with or without task strategy. The task strategy groups were given a specific task strategy to aid learning, while the no task strategy groups received no such instructions. Participants walked on a treadmill while viewing real-time feedback of their steps on a monitor. Walking consisted of four phases: Baseline (2 min), Learning 1 (10 min), Catch (30 sec), and Learning 2 (2 min). During Learning phases, the visual display was altered to encourage learning of a new step symmetry pattern. During Catch, participants were instructed to “return to walking normally”. Any difference in step symmetry from Baseline occurring during Catch was attributed solely to implicit learning. The remainder of the total learning was attributed to explicit mechanisms. We found that locomotor learning using a conscious strategy was impaired in individuals with MCI, and the impairment predominantly affected the explicit learning component. Implicit learning remained intact. Thus, impaired motor learning in individuals with MCI appears to be a result of reduced explicit learning mechanisms. This work suggests that when people with MCI or other cognitive impairments learn new movement skills (i.e., in rehabilitation), the learning should target implicit learning mechanisms to the greatest extent possible, to avoid impaired explicit learning processes.