Glutamatergic modulation of transcranial direct current stimulation over the premotor cortex combined with peripheral nerve stimulation promotes observation–execution‐related cortical excitability and motor performance

Abstract

Action observation and execution, transcranial direct current stimulation (tDCS) and peripheral nerve stimulation (PNS) enhance motor performance. This study aimed to investigate the effect of concurrent tDCS over the premotor cortex (PMC) and PNS during action observation on motor cortex excitability and motor performance, and its underlying mechanisms. One hundred and twenty‐eight healthy adults were randomly assigned to tDCS + PNS combined with presentation of a landscape picture (tDCS + PNS _landscape ), and tDCS + PNS, tDCS _sham + PNS _sham , tDCS _sham + PNS and tDCS + PNS _sham combined with action observation, all followed by two action execution blocks. Motor‐evoked potentials (MEPs), intracortical facilitation (ICF) and short‐interval intracortical inhibition (SICI) were assessed before interventions (T0), immediately after interventions (T1) and after the first action execution block (T2). Reaction times were recorded for both action execution blocks (RT1 and RT2). tDCS + PNS significantly increased MEP amplitudes at T1 and T2 compared to tDCS _sham + PNS _sham and tDCS + PNS _landscape . ICF increased at T1 in the tDCS + PNS group compared to tDCS _sham + PNS _sham and tDCS + PNS _landscape , as well as at T2 relative to tDCS _sham + PNS _sham . RT1 and RT2 of the action execution task in the tDCS + PNS group were significantly shorter compared to the tDCS _sham + PNS _sham group. A significant negative relationship between the change in RT and MEP amplitudes emerged at T2 in the tDCS + PNS group. Concurrent application of tDCS and PNS during action observation induced transient neuroplastic alterations in the primary motor cortex and improved motor performance. image