Transcranial magnetic stimulation over contralateral primary somatosensory cortex disrupts perception of itch intensity.

Itch, a complex unpleasant sensation causing the desire to scratch, results from the activity of a network of brain regions. However, the specific functional contributions of individual regions within this network remain poorly understood. We investigated whether contralateral primary and secondary somatosensory cortices (S1, S2) and ipsilateral inferior frontal gyrus (IFG) are critically involved in the cortical processing of acute itch. Continuous theta burst transcranial magnetic stimulation (cTBS) was applied to either S1, S2 or IFG, followed by itch induction using a histamine prick. Results indicate a significant reduction in itch intensity when cTBS was applied to S1. Stimulation of S2 or the IFG was not associated with a significant reduction in itch intensity. The novel finding of an antipruritic effect elicited by disruption of activity in contralateral S1 suggests a causal role of S1 in encoding the sensory-discriminative aspect of itch and might be important in future studies on brain interventions for the treatment of itch.