A transcranial magnetic stimulation protocol of the inferior frontal gyrus to manipulate activity in the interoceptive brain network: a pilot study on heartbeat-evoked potentials

peer reviewedInteroception, the processing and perception of internal bodily signals, plays an important role in symptom perception. As interoception is mediated by the interoceptive brain network (IBN), whereas dysfunctions in the IBN may contribute to symptom generation, a manipulation of activity in the IBN by transcranial magnetic stimulation (TMS) could be a promising approach to normalize potential dysfunctions. Using a network stimulation approach targeting the inferior frontal gyrus (IFG), four participants underwent a TMS protocol to enhance (intermittent theta burst stimulation/iTBS), or to inhibit (continuous/cTBS) IBN activity or a neutral condition (intermediate/imTBS). Heartbeat-evoked potentials (HEPs) from 455-595ms after the cardiac R-wave in a 3x3 cluster around electrode C2, assessed during a heartbeat counting task, served as indicator of IBN activity. HEPs were recorded before and directly after TMS sessions. Average HEP amplitudes descriptively increased after the inhibition (cTBS: +42%; pre: .23; post: .33 μV) and the neutral (imTBS: +102%; pre: .41; post: -. 57 μV) protocol, but decreased after undergoing the enhancement (iTBS: -60 %; pre: .65; post: .26 μV) protocol. However, none of these differences were significant due to the small sample size. Future studies in larger samples sizes have to validate the current findings that iTBS may enhance IBN activity, whereas cTBS has no effect as compared to a neutral condition. In case this validation is successful, the current TMS protocol may be a future approach to normalize IBN activity in somatic symptom disorders