Age-related differences in motor learning, sensorimotor neurochemistry, and cortical reactivity co-occur but are dissociated

Abstract

Age-related declines in motor learning are commonly attributed to changes in sensorimotor neurophysiology. However, direct links between neurochemistry, electrophysiology, and behavior are scarce. Here, we investigated whether age-related differences in GABAergic inhibition and cortical reactivity mediate age-related simple and complex motor learning declines. To do so, we employed magnetic resonance spectroscopy (MRS) and transcranial magnetic stimulation-electroencephalography (TMS-EEG) in twenty younger and eighteen older adults. Age-related effects prevailed across all measures, with robust differences in motor learning capacity, GABA levels and TMS-EEG responses. However, our analysis provided little evidence that GABAergic inhibition and cortical reactivity mediate age-related motor learning declines. Instead, both neurophysiological measures were selectively coupled to each other in a task-dependent manner, while remaining largely dissociated from motor learning outcomes. Overall, our findings demonstrate that age-related differences in local inhibitory neurochemistry, cortical reactivity and motor learning co-occur but do not appear to form a single causal pathway. These results suggest that links between local neurophysiological measures and behavioral decline may be more indirect than commonly assumed and highlight the need for integrative network approaches to study age-related behavioral processes.