Research Paper Volume 12, Issue 5 pp 4617—4640
Alterations of hand sensorimotor function and cortical motor representations over the adult lifespan
- 1 Movement Control and Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Heverlee, Leuven, Belgium
- 2 KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium
- 3 REVAL Research Institute, Hasselt University, Agoralaan, Diepenbeek, Belgium
received: December 12, 2019 ; accepted: March 2, 2020 ; published: March 11, 2020 ;https://doi.org/10.18632/aging.102925
How to Cite
Copyright © 2020 Hehl et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Using a cross sectional design, we aimed to identify the effect of aging on sensorimotor function and cortical motor representations of two intrinsic hand muscles, as well as the course and timing of those changes. Furthermore, the link between cortical motor representations, sensorimotor function, and intracortical inhibition and facilitation was investigated. Seventy-seven participants over the full adult lifespan were enrolled. For the first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscle, cortical motor representations, GABAA-mediated short-interval intracortical inhibition (SICI), and glutamate-mediated intracortical facilitation (ICF) were assessed using transcranial magnetic stimulation over the dominant primary motor cortex. Additionally, participants’ dexterity and force were measured. Linear, polynomial, and piecewise linear regression analyses were conducted to identify the course and timing of age-related differences. Our results demonstrated variation in sensorimotor function over the lifespan, with a marked decline starting around the mid-thirties. Furthermore, an age-related reduction in cortical motor representation volume and maximal MEP of the FDI, but not for ADM, was observed, occurring mainly until the mid-forties. Area of the cortical motor representation did not change with advancing age. Furthermore, cortical motor representations, sensorimotor function, and measures of intracortical inhibition and facilitation were not interrelated.
ADM: abductor digiti minimi muscle; AIC: Akaike Information Criterion; APB: abductor pollicis brevis muscle; AREA: area of cortical motor representation; CMAP: maximum compound muscle action potential (also: M-wave); CS: conditioning stimulus; EMG: electromyography; FDI: first dorsal interosseus muscle; GABA: gamma-aminobutyric acid; ICF: intracortical facilitation; ISI: interstimulus interval; M1: primary motor cortex; MAXME: maximal motor evoked potential; MEP: motor evoked potential; MoCA: Montreal Cognitive Assessment; PP: paired-pulse; PPT: Purdue Pegboad Test; RMS: root mean square; rMT: resting motor threshold; SD: standard deviation; SICI: short-interval intracortical inhibition; SP: single-pulse; TMS: transcranial magnetic stimulation; TS: test stimulus; VOL: volume of cortical motor representation.