Brain structures involved in interoceptive awareness and cardioafferent signal processing: a dipole source localization study.

Afferent signals from the body play an important role for emotional and motivational aspects of behavior. Nevertheless, little is known about the cortical and subcortical structures involved in interoceptive processes. Recently, a functional MRI study demonstrated that insula, somatomotor, and cingulated cortices are activated when subjects focus attention on their heartbeats. Aside from the use of imaging data, cardiac awareness has frequently been studied by using the heartbeat-evoked potential (HEP), a brain wave that appears contingent on the heartbeat. The present study aimed at localizing sources of the HEP. Multichannel EEG was recorded in 44 subjects while they performed a heartbeat perception task. This task was used to quantify interoceptive awareness and to subdivide the subjects into good and poor heartbeat perceivers. Analyses showed highest HEP amplitudes over frontal and frontocentral electrode locations in the time range of later than 200 ms after R-wave onset. By means of a BESA dipole-source-analysis, four sources of the HEP were identified which were located in the anterior cingulate, the right insula, the prefrontal cortex, and the left secondary somatosensory cortex. Good heartbeat perceivers showed both significantly higher HEP amplitudes and higher dipole strength than poor heartbeat perceivers in all four cortical sources. We conclude that the identified structures are involved in the processing of cardiac signals, whereby anterior cingulate and right insula seem to serve as interoceptive centers for cardioception.