Failure to Engage Neural Plasticity through Practice of a High-difficulty Task is Accompanied by Reduced Motor Skill Retention in Older Adults

Josje M Bootsma,Simone R Caljouw,Menno P Veldman,Natasha M Maurits,John C Rothwell,Tibor Hortobágyi

doi:10.1016/j.neuroscience.2020.10.013

Abstract

While the difficulty of a motor task can act as a stimulus for learning in younger adults, it is unknown how task difficulty interacts with age-related reductions in motor performance and altered brain activation. We examined the effects of task difficulty on motor performance and used electroencephalography (EEG) to probe task-related brain activation after acquisition and 24-h retention of a mirror star-tracing skill in healthy older adults (N = 36, 65–86 years). The results showed that the difficulty of the motor skill affected both the magnitude of motor skill learning and the underlying neural mechanisms. Behavioral data revealed that practicing a motor task at a high difficulty level hindered motor skill consolidation. The EEG data indicated that task difficulty modulated changes in brain activation after practice. Specifically, a decrease in task-related alpha power in frontal and parietal electrodes was only present after practice of the skill at the low and medium, but not the high difficulty level. Taken together, our findings show that a failure to engage neural plasticity through practice of a high-difficulty task is accompanied by reduced motor skill retention in older adults. The data help us better understand how older adults learn new motor skills and might have implications for prescribing motor skill practice according to its difficulty in rehabilitation settings.

Highlights

The ability to acquire and retain motor skills facilitates the recovery from injuries caused by orthopedic or neurological conditions and functional independence in old age (Winstein, 1991; Krakauer, 2006)
There is no clear understanding of how task difficulty affects motor skill learning and if it interacts with age-related modifications in motor performance and brain activation
Improvements in accuracy, but not speed, became consolidated into memory, as evidenced by performance stabilization at the 24-h retention test. These consolidation effects were modulated by difficulty of the practice condition because accuracy at 24-h retention relative to pre-training was worse in P-HD compared to P-LD and PMD

Summary

Introduction

The ability to acquire and retain motor skills facilitates the recovery from injuries caused by orthopedic or neurological conditions and functional independence in old age (Winstein, 1991; Krakauer, 2006). Motor skill learning is the process of practice-dependent improvement of motor performance and emerges as an interplay between motor and cognitive systems (Lee et al, 1994; Krakauer et al, 2019). There is no clear understanding of how task difficulty affects motor skill learning and if it interacts with age-related modifications in motor performance and brain activation. Insights into this interaction could help optimize motor skill learning in older adults and patients recovering from movement impairments

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