Age-Related Differences in Corticospinal Excitability and Anticipatory Postural Adjustments of the Trunk

Rebecca S Rowland; Ned Jenkinson; Shin-Yi Chiou

doi:10.3389/fnagi.2021.718784

Age-Related Differences in Corticospinal Excitability and Anticipatory Postural Adjustments of the Trunk

Front Aging Neurosci. 2021 Aug 17:13:718784. doi: 10.3389/fnagi.2021.718784. eCollection 2021.

Authors

Rebecca S Rowland¹, Ned Jenkinson^{1

2

3}, Shin-Yi Chiou^{1

2

3}

Affiliations

¹ School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom.
² Centre for Human Brain Health, University of Birmingham, Birmingham, United Kingdom.
³ Medical Research Council 'Versus' Arthritis Centre for Musculoskeletal Ageing Research, University of Birmingham, Birmingham, United Kingdom.

Abstract

Anticipatory postural adjustments (APAs) are a feedforward mechanism for the maintenance of postural stability and are delayed in old adults. We previously showed in young adults that APAs of the trunk induced by a fast shoulder movement were mediated, at least in part, by a cortical mechanism. However, it remains unclear the relationship between delayed APAs and motor cortical excitability in ageing. Using transcranial magnetic stimulation we examined motor evoked potentials (MEPs) of the erector spinae (ES) muscles in healthy young and old adults prior to a fast shoulder flexion task. A recognition reaction time (RRT) paradigm was used where participants responded to a visual stimulus by flexing their shoulders bilaterally as fast as possible. The activity of bilateral anterior deltoid (AD) and ES muscles was recorded using electromyography (EMG). The onset of AD and ES EMG was measured to represent RRT and APAs, respectively. We found increases in amplitudes of ES MEPs at 40 ms than 50 ms prior to the EMG onset of the AD in both groups. The amplitude of ES MEPs at 40 ms prior to the onset of AD EMG correlated with the onset of ES activity counterbalancing the perturbation induced by the shoulder task in the elderly participants only. Our findings suggest that timing of increasing corticospinal excitability prior to a self-paced perturbation becomes more relevant with ageing in modulating postural control of the trunk.

Keywords: anticipatory postural adjustments; balance; corticospinal excitability; electromyography; erector spinae; motor evoked potentials; older adults.