Peripheral nerve stimulation synchronized with brain stimulation facilitates somatosensory function

We developed a peripherocentral synchronized stimulation (pcSS) system which enables peripheral nerve stimulation synchronized with transcranial alternating current stimulation (tACS). We investigated the neuromodulatory effects of pcSS to the median nerve and the primary somatosensory cortex (S1) on the somatosensory function and the excitability of the S1 in healthy humans by assessing the two point discrimination (TPD) test and somatosensory evoked potential (SEP).

Twenty adults participated in this study. tACS was delivered across the right S1. The frequency was individually determined based on the latency of SEP. The left median nerve was stimulated at the specific phases (0 and π) of the tACS.

pcSS with the phase of 0, in which the median nerve stimulation was carried to the S1 at the timing when the peak current flowed in the posterior-anterior direction across the S1, the TPD threshold was decreased and the SEP amplitude was increased. Either pcSS with the phase of π or the median nerve stimulation without tACS did not alter the outcomes.

pcSS induced the different effects depending on the phases of tACS when the peripheral nerve was stimulated.

pcSS has the potential to become a new intervention for somatosensory rehabilitation.