Modulation of motor cortical excitability by paired associative stimulation (PAS) of the primary somatosensory cortex

Introduction: The primary somatosensory cortex (S1) plays a crucial role in learning and adapting of motor skills. Due to the high interconnectedness to primary motor cortex (M1), manipulation of S1 excitability offers an opportunity to alter M1 excitability function. We applied paired associative stimulation (PAS) to S1 in order to induce long-term potentiation (LTP)-like or long-term depression (LTD)-like effects in S1 and evaluated the consequences of S1-PAS on excitability in the adjacent M1. Methods: 12 young healthy right-handed subjects participated in 5 experimental sessions in a randomized crossover des…