The insula was named insula Reilii in 1796 by Johann Christian Reil, who described its hidden island-like position beneath the opercula. Until the late twentieth century it was considered a vestigial olfactory or limbic structure with little distinctive function. Two threads of work changed that: A.D. Craig’s elaboration of the lamina-I-to-insular pathway as the cortical termination of an interoceptive system, and Antonio Damasio’s somatic-marker hypothesis placing the insula at the intersection of bodily and emotional states.

The dorsal anterior insula and adjacent inferior frontal cortex form the “salience network” identified by Seeley and colleagues, anchored by von Economo neurons (large, bipolar projection cells found predominantly in humans, great apes, and a handful of other large-brained mammals). Selective vulnerability of these neurons may contribute to the early anterior-insula atrophy seen in behavioural-variant frontotemporal dementia.

Insular damage was also shown by Naqvi and colleagues to produce sudden, sustained remission of nicotine addiction in a small number of patients, demonstrating that the insula’s role in interoceptive processing extends into the maintenance of drug-seeking behaviour. This finding has motivated experimental insular-cortex transcranial magnetic stimulation as an addiction treatment.