Understanding the neural bases of bodily self-consciousness: recent achievements and main challenges

Abstract

The last two decades have seen a surge of interest in the mechanisms underpinning bodily self-consciousness (BSC). Studies showed that BSC relies on several bodily experiences (i.e., self-location, body ownership, agency, first-person perspective) and multisensory integration. The aim of this literature review is to summarize new insights and novel developments into the understanding of the neural bases of BSC, such as the contribution of the interoceptive signals to the neural mechanisms of BSC, and the overlap with the neural bases of conscious experience in general and of higher-level forms of self (i.e., the cognitive self). We also identify the main challenges and propose future perspectives that need to be conducted to progress into the understanding of the neural mechanisms of BSC. In particular, we point the lack of crosstalk and cross-fertilization between subdisciplines of integrative neuroscience to better understand BSC, especially the lack of research in animal models to decipher the neural networks and systems of neurotransmitters underpinning BSC. We highlight the need for more causal evidence that specific brain areas are instrumental in generating BSC and the need for studies tapping into interindividual differences in the phenomenal experience of BSC and their underlying mechanisms.

Keywords: body representation; consciousness; multisensory integration; neuroimaging; self-consciousness.

FIGURE 1

Heartbeat evoked potentials and bodily self-consciousness (BSC) in a full-body illusion. (A) Participants received on their back a tactile stimulation either synchronously or asynchronously with a video of their own back being stroked in a head-mounted display. (B) Participants answered a questionnaire about BSC (e.g., self-identification with the seen body) after five exposures to visuo-tactile stimulation. (C) Electrocardiogram was recorded during the visuo-tactile stimulation. Arrows indicate cardiac R-peaks. (D) Difference in activation by heartbeats between synchronous and asynchronous visuo-tactile stimulation was significant in the bilateral posterior cingulate cortex. Reproduced from Park et al. (2016).

FIGURE 2

Responses elicited by electrical stimulation of the cortex in awake epileptic patients. (A) Circles represent the location of electrical stimulation applied in different epileptic patients. Red circles are sites where electrical stimulation evoked a change in the conscious experience or a motor response, whereas black circles are sites where no response was evoked. (B) The color code represents the mean response rate, showing high response rate in somato-motor and visual networks and low response rate in the default and limbic networks and in other transmodal networks. Reproduced from Raccah et al. (2021). (C) Color-coded density maps showing the number of electrical brain stimulation evoking disturbances of the bodily self in a systematic review of the literature, showing six main areas underlying the bodily self. MCC, middle cingulate cortex; SMA, supplementary motor area. Brain images have been flipped horizontally to allow comparisons with part (B). Reproduced from Dary et al. (2023).

FIGURE 3

Structural connectivity underlying the sense of body ownership. Representation of the tracts damaged more frequently in stroke patients with disturbed sense of body part ownership when compared to patients whose sense of body part ownership was not affected. EBA, extrastriate body area; IPS, intraparietal sulcus; PMv, ventral premotor cortex. Reproduced from Errante et al. (2022).

FIGURE 4

Levels of analysis within the field of integrative neuroscience to decipher the neural bases of bodily self-consciousness (BSC) and examples of techniques and approaches. Dashed lines indicate the levels of analysis that have been overlooked.