Motor cortex plasticity induced by paired associative stimulation is enhanced in physically active individuals

Abstract

Recent evidence indicates that regular physical activity enhances brain plasticity (i.e. the ability to reorganise neural connections) and improves neurocognitive function. However, the effect of regular physical activity on human motor cortex function is unknown. The purpose of this study was to examine motor cortex plasticity for a small hand muscle in highly active and sedentary individuals. Electromyographic recordings were obtained from the left abductor pollicis brevis (APB) muscle of 14 active and 14 sedentary subjects (aged 18-38 yrs). The extent of physical activity was assessed by questionnaire, where the physically active subjects performed >150 min per day moderate-to-vigorous aerobic activity on at least 5 days per week, whereas the sedentary group performed <20 min per day of physical activity on no more than 3 days per week. Transcranial magnetic stimulation (TMS) of the right hemisphere was used to assess changes in APB motor-evoked potentials (MEPs), input-output curve (IO curve), short-interval intracortical inhibition (SICI) and cortical silent period (CSP). Neuroplastic changes were induced using paired-associative stimulation (PAS), which consisted of 90 paired stimuli (0.05 Hz for 30 min) of median nerve electrical stimulation at the wrist followed 25 ms later by TMS to the hand area of motor cortex. The IO curve slope was 35% steeper in individuals with increased physical activity (combined before and after PAS, P < 0.05), suggesting increased motor cortex excitability, although there was no difference in SICI or CSP between groups. PAS induced an increase in MEP amplitude in the physically active subjects (54% increase compared with before, P < 0.01), but no significant facilitation in the sedentary subjects. We conclude that participation in regular physical activity may offer global benefits to motor cortex function that enhances neuroplasticity, which could improve motor learning and neurorehabilitation in physically active individuals.

Inter- and intra-subject variability of motor cortex plasticity following continuous theta-burst stimulation

“…We have also shown that the physical activity history of an individual can influence rTMS-induced neuroplastic responses (Cirillo et al 2009). Here, we were interested in examining whether simple questionnaire-based assessments of physical activity or stress (surrogate for cortisol) could be used to explain some of the variability in neuroplastic responses.…”

“…A number of these identified factors contribute to inter-subject response variability, such as age (Fathi et al 2010;Muller-Dahlhaus et al 2008;Tecchio et al 2008;Todd et al 2010), genetics (Cheeran et al 2008), and motor cortical physiology (Hamada et al 2013). However, several factors have been identified that could contribute to both inter-and intra-subject response variability, such as an individual's history of physical activity (Cirillo et al 2009) and levels of the stress hormone cortisol (Clow et al 2014;Sale et al 2008).…”

Stimulus uncertainty enhances long-term potentiation-like plasticity in human motor cortex

“…Such an approach has been used by many other subsequent studies employing PAS (e.g., Cirillo, Lavender, Ridding, & Semmler, 2009;Di Lazzaro et al, 2009;Fratello et al, 2006;Player, Taylor, Alonzo, & Loo, 2012). Critically, however, in all variants of PAS, the pairing of the peripheral and cortical stimulation occurs in a regular and entirely predictable manner, which would appear to make it non-optimal for inducing learning-related changes.…”

Transcranial Magnetic Stimulation to Investigate Motor Cortical Circuitry and Plasticity in Spinal Cord Injury

“…PAS-induced increases in corticospinal excitability are mediated by glutamate and are blocked in the presence of NMDA receptor antagonists [89]. PAS effects are strongly dependent on the focus of directed attention ss [91] circadian rhythm [92], physical exercise [93] and are thought to be mediated by changes in cortical [87] and spinal circuitry [94]. In incomplete SCI, a modified PAS protocol for the TA muscle was performed whereby single-pulse TMS over the TA representation in M1 was paired with stimulation to the CPN (i.e.…”