Cerebellar Brain Inhibition and Its Association with Motor Inhibition and Reaction Time In Younger and Older Adults.

Motor performance declines with age, particularly affecting reaction time and proactive response inhibition. While cortical influences on age-related motor decline are well-documented, the cerebellum's role remains unclear. Cerebellar Brain Inhibition (CBI), which can be measured through dual-site transcranial magnetic stimulation (TMS), may provide insights into age-related changes in motor control. We aimed to (1) compare resting-state CBI between young and older adults, (2) investigate the relationship between CBI and upper limb motor performance, and (3) examine whether this relationship differs between age groups. Using dual-site TMS, resting-state CBI was assessed in young and older adults. Motor performance was evaluated using a task battery measuring simple and choice reaction times, and response inhibition. As expected, older adults exhibited significantly longer reaction times and reduced reactive inhibition with lower accuracy compared to younger adults. No significant differences in resting CBI were observed between age groups, and no association was found between CBI and motor performance outcomes. Despite clear age-related differences in motor performance, resting CBI revealed no difference between age groups and showed no association with motor control measures. These findings suggest that the effect of aging on dual-site TMS-derived cerebellar inhibition at rest and its association with motor performance might be limited. However, age-related cerebellar effects on motor control might manifest during task execution rather than at rest, highlighting the potential importance of investigating CBI modulation during motor performance in the context of aging.