Inhibiting anterior insula changes interoceptive accuracy: a combined TMS-fMRI study

The insular cortex (IC) is involved in sensing and interpreting visceral signals, an ability called interoception, the lack of which is considered a transdiagnostic risk factor for psychopathology. It is still unknown whether it is possible to modulate insular activity to change interoception using noninvasive brain stimulation techniques. Transcranial magnetic stimulation, including theta-burst stimulation (TBS), has proven to be an effective method to non-invasively modulate cortical regions' activity, producing facilitatory (iTBS) or inhibitory (cTBS) effects. By combining TBS with fMRI, we hypothesized that iTBS and cTBS would affect IC activity and, consequently, interoception. Thirty-six participants (18 F; Mage: 23.78 ± 3.56 years) volunteered for this study. cTBS and iTBS, over the right anterior insula, and sham stimulation over vertex were administered in a counterbalanced order across participants. After each stimulation, participants performed the heartbeat counting task and were scanned while performing an explicit emotional judgment task. During this task, they saw disgusting (or, as control, neutral) images that have proven to consistently activate the insula. We found preliminary evidence indicating that cTBS is able to change bilateral anterior IC activation. Specifically, cTBS reduced the bilateral activation of the IC during disgusting blocks and reduced participants’ ability to accurately detect their heartbeats compared to sham. Given the growing use of TMS protocols in psychiatry, current results could be used to inform the conduction of clinical trials aimed at actively changing the IC activity, for example, in patients showing alterations in interoception (e.g., anxiety disorders) or increased disgust sensitivity (e.g., obsessive-compulsive disorders).