“Promoting the modulatory capacity of intracortical inhibition in young and old: interrelation of physical exercise and sleep”

Lay summary
The human cortical inhibitory system is known to play a crucial role for normal brain development, function and plasticity thereby acting on both, cognitive and motor processes. Furthermore, cortical inhibition is crucial for sleep induction and sleep maintenance. The principal inhibitory neurotransmitter in the central nervous system is gamma-aminobutyric acid (GABA). There is first evidence from our lab that not only the general amount of GABAergic inhibition is crucial with respect to motor control and motor learning but rather the capacity to task- and phase-specifically modulate GABA release, i.e. the modulatory range. Furthermore, modulation of GABA release is also vital for sleep induction and sleep maintenance. Most pharmacological interventions manipulating sleep behavior involve GABAergic mechanisms. In addition, studies with transcranial magnetic stimulation (TMS) have demonstrated that short-interval intracortical inhibition (SICI) is up-, and corticospinal excitability is down-regulated during increased sleepiness and that this modulation further proceeds when falling asleep while being entirely suppressed during awakening. Furthermore, it is known that physical activity (e.g. balance exercises) can enhance sleep quality and it is also known that sleep influences motor performance as well as motor memory consolidation. Therefore, the aim of the current study is to investigate the close reciprocal interrelation of physical activity and sleep on the mechanistic and behavioral level. This could be of great significance as there is growing recognition of the importance of sleep to improve population health due to the convincing evidence linking sleep to a range of health outcomes.