Effect of transcranial DC sensorimotor cortex stimulation on somatosensory evoked potentials in humans

OBJECTIVE To study the after-effect of transcranial direct current stimulation (tDCS) over the sensorimotor cortex on the size of somatosensory evoked potentials (SEPs) in humans. METHODS SEPs were elicited by electrical stimulation of right or left median nerve at the wrist before and after anodal or cathodal tDCS in 8 healthy subjects. tDCS was applied for 10 min to the left motor cortex at a current strength of 1 mA. RESULTS Amplitudes of P25/N33, N33/P40 (parietal components) and P22/N30 (frontal component) following right median nerve stimulation were significantly increased for at least 60 min after the end of anodal tDCS, whereas P14/N20, N20/P25 (parietal components) and N18/P22 (frontal component) were unaffected. There was no effect on SEPs evoked by left median nerve stimulation. Cathodal tDCS had no effect on SEPs evoked from stimulation of either arm. CONCLUSIONS Anodal tDCS over the sensorimotor cortex can induce a long-lasting increase in the size of ipsilateral cortical components of SEPs. SIGNIFICANCE tDCS can modulate cortical somatosensory processing in humans and might be a useful tool to induce plasticity in cortical sensory processing.

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