Changes in interoceptive processes following brain stimulation

Abstract

The processing and perception of individual internal bodily signals (interoception) has been differentiated to comprise different levels and processes involved. The so-called heartbeat-evoked potential (HEP) offers an additional possibility to examine automatic processing of cardiac signals. Knowledge on neural structures potentially supporting different facets of interoception is still sparse. One way to get insights into neuroanatomical function is to manipulate the activity of different brain structures. In this study, we used repetitive transcranial magnetic stimulation (rTMS) and a continuous theta-burst protocol to inhibit specific central locations of the interoceptive network including the right anterior insula and the right somatosensory cortices and assessed effects on interoceptive facets and the HEP in 18 male participants. Main results were that inhibiting anterior insula resulted in a significant decline in cardiac and respiratory interoceptive accuracy (IAc) and in a consistent decrease in perception confidence. Continuous theta-burst stimulation (cTBS) over somatosensory cortices reduced only cardiac IAc and affected perception confidence. Inhibiting right anterior insula and right somatosensory cortices increased interoceptive sensibility and reduced the HEP amplitude over frontocentral locations. Our findings strongly suggest that cTBS is an effective tool to investigate the neural network supporting interoceptive processes.This article is part of the themed issue 'Interoception beyond homeostasis: affect, cognition and mental health'.

Keywords: HEP; TMS; insula; interoception; interoceptive accuracy; somatosensory cortex.

© 2016 The Author(s).

Figures

Figure 1.

Experimental procedure. Anatomical details of the sites of stimulation are depicted using EEG positions and structural MRI pictures together with TMS target locations.

Figure 2.

Cardiac and respiratory interoceptive accuracy (n = 18; mean scores ± s.e.m.) contrasting the three cTBS locations. (Asterisks represent a significant difference; *p < 0.05.)

Figure 3.

Cardiac and respiratory confidence (n = 18; mean scores ± s.e.m.) contrasting the three cTBS locations. (Asterisks represent a significant difference; *p < 0.05.)

Figure 4.

Group (n = 18) average (±s.e.m.) effect of cTBS on interoceptive sensibility as assessed by state questionnaire. (Asterisks represent a significant change in subjective report; **p < 0.01; ***p < 0.001.)

Figure 5.

(a) HEP amplitudes at right frontocentral and central locations (FC6, C6). (b) HEP scalp distribution at 500 ms post R-wave. (c) HEP distribution over 19 electrodes.