Neural divergence and convergence for attention to and detection of interoceptive and somatosensory stimuli

Abstract

1Body awareness is constructed by signals originating from within and outside the body. How do 2 these apparently divergent signals converge? We developed a signal detection task to study the 3 neural convergence and divergence of interoceptive and somatosensory signals. Participants focused 4 on either cardiac or tactile events and reported their presence or absence. Beyond some evidence of 5 divergence, we observed a robust overlap in the pattern of activation evoked across both conditions 6 in frontal areas including the insular cortex, as well as parietal and occipital areas, and for both 7 attention and detection of these signals. Psycho-physiological interaction analysis revealed that right 8 insular cortex connectivity was modulated by the conscious detection of both types of sensations, 9but with greater connectivity to occipito-parietal regions when attending to cardiac signals. Our 10 findings speak in favour of the inherent convergence of bodily-related signals and move beyond the 11 apparent antagonism between exteroception and interoception. 12 2015; Zaki et al.,

Increasing familiarity with the heartbeat counting task does not affect performance

“…Another possible explanation for the difference may be due to the fact that participants in the former study were counting heartbeats with their eyes closed and time intervals used in the task were shorter (18/20/22 seconds). The observed correlation between HCT and VCT performance also corresponds with another study, comparing heartbeat perception with somatosensory stimuli (Herman et al, 2020). Although direct comparison is not possible due to the modification of the heartbeat counting task used in that study, our findings support the idea of overlapping mechanisms between interoception and exteroception.…”

“…This prompts a second question about the HCT, namely whether performance levels in it reflect interoceptive accuracy per se or if they instead also reflect individual propensities for the reporting of uncertain stimuli in general. Evidence that this may be the case comes from prior work demonstrating correlations between reporting behaviour in the HCT and in matched somatosensory and auditory tasks (Herman et al, 2020;Larsson et al, 2020).…”

Blind individuals’ enhanced ability to sense their own heartbeat is related to the thickness of their occipital cortex

“…In sighted individuals, performance on tasks involving cardiac interoception has been consistently linked to activation of regions related to the processing of visceral interoceptive signals, such as the insular cortex (Cameron & Minoshima, 2002;Critchley et al, 2004;Herman et al, 2021;Stern et al, 2017;Zaki et al, 2012) and the anterior cingulate cortex (Caseras et al, 2013;García-Cordero et al, 2016;Khalsa et al, 2009;Kleckner et al, 2017). However, in our study, no associations were observed between cardiac interoception and cortical thickness in these regions, for both blind and sighted participants.…”

“…By contrast,Herman, Palmer, Azevedo, & Tsakiris (2021) have demonstrated that attention to and detection of interoceptive signals can lead to increased activations of the occipital cortex, potentially pointing to a functional role of the occipital cortex during interoceptive tasks. The exact relationship between visceral signal processing and the occipital cortex in sighted individuals remains to be clarified (see Azzalini, Rebollo, & Tallon-Baudry, 2019).…”