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

Abstract

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.

A cortical potential reflecting cardiac function

“…Our work is predicated on studies describing afferent ''interoceptive'' potentials triggered on the heart (17)(18)(19)(20)29). However, in contrast to previous findings, our research represents a demonstration of cortically recorded indices of cardiac function in a clinical population.…”

“…Electroencephalography (EEG) has higher temporal resolution than techniques such as positron emission tomography or functional MRI (fMRI), although is limited with respect to inferring neuroanatomical generators of surface potentials. EEG methods have been applied to the study of afferent cardiac signals, where a heartbeat-evoked potential (HEP) has been described (17)(18)(19)(20). The circumscribed location of this HEP to frontal and central scalp (17,18,21,22) and particularly the observation that its amplitude predicts individual differences in interoceptive awareness (accuracy of heartbeat perception) (19) is consistent with a cardiac afferent source, arising from myocardial, carotid sinus and/or aortic arch baroreceptors, or perhaps mechanoreceptors within tissue distended by ejected blood (23)(24)(25).…”

Feeling, learning from and being aware of inner states: interoceptive dimensions in neurodegeneration and stroke

“…It consists of a negative deflection in central and frontal electrodes [5] within a 200 -400 ms window post-R wave [11,46]. As this component is modulated by attention to heartbeats [46], it indexes interoceptive processes without involvement of learning mechanisms. Thus, following previous studies [17,46], we measured this potential only during the interoceptive accuracy condition, around an extended frontal region of interest (ROI) encompassing 33 electrodes (figure 2), focusing on the maximum HEP modulation described over frontal electrodes [46].…”

“…As this component is modulated by attention to heartbeats [46], it indexes interoceptive processes without involvement of learning mechanisms. Thus, following previous studies [17,46], we measured this potential only during the interoceptive accuracy condition, around an extended frontal region of interest (ROI) encompassing 33 electrodes (figure 2), focusing on the maximum HEP modulation described over frontal electrodes [46]. We also assessed three separate four-electrode ROIs in frontal-right, -left and -central topographies.…”

Brain Responses to Cardiac Electrical Stimulation: A New EEG Method for Evaluating Cardiac Sensation

“…Second, since electrical stimulation synchronously contracts the heart, it could also activate afferent receptors outside the heart, such as the great vessel baroreceptors and somatosensory receptors of the chest. Third, the results of heart cyclerelated EEG averaging are substantially contaminated by the cardiac electrical field (Dirlish et al 1997(Dirlish et al , 1998Pollatos and Schandry 2004;Pollatos et al 2005) (Fig. 1).…”