Peripheral transcutaneous electrical stimulation to improve cognition: a review of the main effects in healthy humans and in mildly cognitively impaired patient populations

Peripheral nerve stimulation (PNS) is an ancient technique, up to now mainly used for pain management. The least invasive approach for PNS is transcutaneous electrical stimulation (TENS), which is performed by delivering mild electric currents through the skin and, depending on the stimulation pattern, activates the somatosensory A beta-, A delta- and C-fibers. In addition to its use for pain relief, accumulating data indicates that TENS can have broadspectrum cognitive effects through the activation of neuromodulatory brain pathways. This review aims to summarize the current evidence on the cognitive effects of TENS, from healthy participants and mildly cognitively affected patients. Most studies on this topic have investigated the effects of TENS on memory, while fewer studies have explored attention, executive functions, and verbal fluency. Overall, promising evidence suggests that TENS may exert positive effects on specific cognitive functions. Further research is needed to build consensus on the most effective stimulation protocols, for both neurorehabilitation and enhancement, and to better understand the neurobiological mechanisms underlying the cognitive effects of TENS.