Abstract
While in young adults (YAs) the underlying neural mechanisms of motor learning are well-studied, studies on the involvement of the somatosensory system during motor skill learning in older adults (OAs) remain sparse. Therefore, the aim of the present study was to investigate motor learning-induced neuroplasticity in the primary somatosensory cortex (S1) in YAs and OAs. Somatosensory evoked potentials (SEPs) were used to quantify somatosensory activation prior and immediately after motor skill learning in 20 right-handed healthy YAs (age range: 19–35 years) and OAs (age range: 57–76 years). Participants underwent a single session of a 30-min co-contraction task of the abductor pollicis brevis (APB) and deltoid muscle. To assess the effect of motor learning, muscle onset asynchrony (MOA) between the onsets of the contractions of both muscles was measured using electromyography monitoring. In both groups, MOA shortened significantly during motor learning, with YAs showing bigger reductions. No changes were found in SEP amplitudes after motor learning in both groups. However, a correlation analysis revealed an association between baseline SEP amplitudes of the N20/P25 and N30 SEP component and the motor learning slope in YAs such that higher amplitudes are related to higher learning. Hence, the present findings suggest that SEP amplitudes might serve as a predictor of individual motor learning success, at least in YAs. Additionally, our results suggest that OAs are still capable of learning complex motor tasks, showing the importance of motor training in higher age to remain an active part of our society as a prevention for care dependency.
Highlights
We are confronted with an aging society worldwide (He et al, 2016), which in turn has a huge impact on the health care and social system
To fully answer the question, whether a longer task duration may have resulted in a stronger S1 amplitude change, future studies are needed, which should take into account that different motor learning stages exist, which are linked to different recruited networks. Apart from these divergent Somatosensory evoked potentials (SEPs) findings, we showed that the baseline SEP amplitudes could be used as a predictor for motor learning outcomes, at least in young adults (YAs)
There are studies suggesting that in old age, SEP amplitudes increase independent of task performance (Lüders, 1970; Kazis et al, 1983; Huttunen et al, 1999; Stephen et al, 2006). Contradictory to these findings, our results show no differences in SEP amplitudes between YAs and older adults (OAs) neither at baseline level nor post motor learning
Summary
We are confronted with an aging society worldwide (He et al, 2016), which in turn has a huge impact on the health care and social system. On a functional level, impaired somatosensory skills are associated with higher risks of falls (Lord et al, 1999). This functional relation between both areas can be explained by the strong interconnectedness of motor and somatosensory systems via neuronal cortico-cortical projections (Porter, 1992, 1997), which are potentially mediated by -amino butyric acid (GABA) transmission (Pleger et al, 2003)
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