Neural Correlates of Motor Skill Learning Are Dependent on Both Age and Task Difficulty

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

doi:10.3389/fnagi.2021.643132

Abstract

Although a general age-related decline in neural plasticity is evident, the effects of age on neural plasticity after motor practice are inconclusive. Inconsistencies in the literature may be related to between-study differences in task difficulty. Therefore, we aimed to determine the effects of age and task difficulty on motor learning and associated brain activity. We used task-related electroencephalography (EEG) power in the alpha (8–12 Hz) and beta (13–30 Hz) frequency bands to assess neural plasticity before, immediately after, and 24-h after practice of a mirror star tracing task at one of three difficulty levels in healthy younger (19–24 yr) and older (65–86 yr) adults. Results showed an age-related deterioration in motor performance that was more pronounced with increasing task difficulty and was accompanied by a more bilateral activity pattern for older vs. younger adults. Task difficulty affected motor skill retention and neural plasticity specifically in older adults. Older adults that practiced at the low or medium, but not the high, difficulty levels were able to maintain improvements in accuracy at retention and showed modulation of alpha TR-Power after practice. Together, these data indicate that both age and task difficulty affect motor learning, as well as the associated neural plasticity.

Highlights

Unfavorable structural, functional, and biochemical changes in the nervous system affect the speed and accuracy of movements in older adults (Smith et al, 1999; Seidler et al, 2010)
With regard to the NASAtlx, Kruskal-Wallis tests confirmed that task difficulty affected the overall perceived mental workload only in younger adults (Supplementary Table 1 and Supplementary Figure 1) such that it was 49% higher in P-HD compared to P-LD (p = 0.006)
The present study aimed to determine the effects of age and task difficulty on motor learning and associated neural plasticity

Summary

Introduction

Unfavorable structural, functional, and biochemical changes in the nervous system affect the speed and accuracy of movements in older adults (Smith et al, 1999; Seidler et al, 2010). If and how old age affects the acquisition and retention of new motor skills is still under debate (VoelckerRehage, 2008; Coats et al, 2014). Motor practice can modify the structure and function of neural populations involved in motor skill acquisition and retention (Kolb et al, 2003; Pascual-Leone et al, 2005). A general age-related decline in such neural plasticity is evident (Reuter-Lorenz and Park, 2010; Pascual-Leone et al, 2011), the age-effects on neural plasticity after a period of motor practice are inconclusive (King et al, 2013; Cai et al, 2014). Understanding the effects of age on motor learning and practice-related plasticity is important to aid functional independence of older adults in increasingly aging societies and to develop novel rehabilitation practice schemes.

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