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 Key points The integration of motor observation and action execution enhances motor performance, with similar brain networks playing key roles in this process. However, the effect of concurrent application of transcranial direct current stimulation (tDCS) over the premotor cortex and peripheral nerve stimulation (PNS) during action observation on observation–execution‐related motor cortex excitability and motor performance and the underlying mechanism is lacking in the literature. Simultaneous application of brain (anodal tDCS over the premotor cortex) and peripheral nerve (PNS over the ulnar nerve) stimulation during action observation induced transient neuroplastic alterations in the primary motor cortex and improved motor performance. Since this dual‐stimulation method strengthens brain pathways related to movement, it could be especially useful for people recovering from conditions like stroke, where active movement is limited.