Visuomotor task acquisition is reduced by priming paired associative stimulation in older adults

Transcranial magnetic stimulation may represent an effective means for improving motor function in the elderly. The aim of this study was therefore to investigate the effects of paired associative stimulation (PAS; a plasticity-inducing transcranial magnetic stimulation paradigm) on acquisition of a novel visuomotor task in young and older adults. Fourteen young (20.4 ± 0.6 years) and 13 older (69.0 ± 1.6 years) adults participated in 3 experimental sessions during which training was preceded (primed) by PAS. Within each session, the interstimulus interval used for PAS was set at either the N20 latency plus 5 ms (PASLTP), the N20 latency minus 10 ms (PASLTD), or a constant 100 ms (PASControl). After training, the level of motor skill was not different between PAS conditions in young subjects (all p-values > 0.2), but was reduced by both PASLTP (p = 0.02) and PASLTD (p = 0.0001) in older subjects. Consequently, priming PAS was detrimental to skill acquisition in older adults, possibly suggesting a need for interventions that are optimized for use in elderly populations. •Paired associative stimulation (PAS) applied to primary motor cortex can influence ballistic motor training in young adults.•The effect of different PAS protocols on visuomotor task performance in older adults is not known.•Different PAS protocols had no influence on visuomotor task performance in young adults.•Altering primary motor cortex excitability with PAS impaired visuomotor task performance in older adults.