12.2 The awareness of one’s body and actions

We perceive our own movements via a process called ‘reafference‘ which involves sensory input from our own body via visual inputs and proprioception, with consequent enhanced recognition of our own behaviour.

The process of reafference, integral to the architecture of the brain organised as superimposed neural loops, is central to the emergence of a self. Every command sent from higher levels is also sent back internally providing an ‘copy’ of what the command was¹. This is often referred to as ‘efference copy’ or ‘corollary discharge’. These signals are sent down in parallel with commands for action and return via ascending pathways to the upper neural loops keeping them informed of the motor commands that have been given. This generates a kind of recording of the plans or intention to move, whilst keeping track of the resultant actions themselves.

Corollary discharge mechanisms require a millisecond coordination between expected and unexpected neuronal events: this process may be mediated by gamma-band activity during normal brain functioning². It is likely that there are multilayered corollary discharge systems in most kinds of motor activity that help distinguish between self-generated and externally generated sensory information. 

The concept of ‘embodiment‘ or ‘embodied cognition‘ describes well the way in which we experience existing as an integral part of our own body, in other words, the feeling that we occupy our own body. The generation of this feeling involves the anterior precuneus in the posteromedial cortex³. Stimulating the anterior precuneus caused individuals to report alterations in their subjective experiences similar to those experienced by people with seizures originating from that region. These changes included a feeling of floating, dizziness, a lack of focus and a sense of detachment from themselves. “The anterior precuneus to be active when individuals’ bodily self-perception was altered using an out-of-body illusion that made participants feel as though their real body was no longer a part of themselves”. Some participants remarked that the detachment was reminiscent of what they’d felt while on psychedelics.

The same area of the brain is active when individuals’ bodily self-perception is altered and made participants feel as though their real body was no longer a part of themselves in out-of-body illusion experiments. Similar states are achieved with sensory deprivation as in water tanks where individuals float in a dark and are cut off from their senses. According to Blanke (2005)⁴, who investigated the neurocognitive mechanisms of the so-called ‘out-of-body experience‘ (OBE), spatial unity, self location, and egocentric visuospatial perspective are three essential phenomenological aspects of the self. Blanke and colleagues suggested that both bodily signals originating from the outside of the body (exteroceptive bodily signals) and internal bodily signals from visceral organs (interoceptive bodily signals) contribute to self-consciousness, and account for its fundamental elements such as self-identification and self-location, as well as the felt experience of on-going spatial unity of the self and body⁵. Electrical stimulation of the nearby temporoparietal junction area induced an illusionary sensation that someone, a ghost shadow, was standing behind the patient⁶. 

Since the 19th century, a major question has been the level of awareness we have of our internal organs (James-Lange theory). Indeed, the absence of voluntary control over most internal organs may be secondary to the absence of sensory awareness of them. While all internal organs are supplied by primary afferent neurons (visceral sensory neurons), we are normally little aware of inputs from these organs except if they are activated by harmful conditions eliciting discomfort or pain. Nevertheless, the insula, a primordial region deep in the cerebral cortex, is involved in the internal sensing of our own body, responding to states such as altered heart rate, gastrointestinal distention, etc⁷. In an early study by Mullan and Penfield (1959)⁸, in response to stimulation of the insula, a subject reported a sensation of “being out of this world”. 

The underlying processes of what the Derek Denton calls “primordial emotions”⁹ involve internal neural loops several levels above the foundational sensory-motor loops, and ensure the complex behaviours of breathing, drinking, and eating necessary to maintain our living biological machine. All internal organs including lungs, heart, blood vessels, gut, etc, are controlled by the subcortical centres and inputs from viscera appear to be involved in shaping a deep sense of self, even when we do not appear to be conscious of it¹⁰. 

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1. JFA Poulet & B Hedwig (2006): New insights into corollary discharges mediated by identified neural pathways. Trends in Neurosciences 30, 14-21. ↩︎
2. C-MA Chen et al (2011): The corollary discharge in humans is related to synchronous neural oscillations. Journal of Cognitive Neuroscience 23, 2892-2904. ↩︎
3. D Lyu et al (2023): Causal evidence for the processing of bodily self in the anterior precuneus. Neuron 111, 2502-2512. ↩︎
4. O Blanke et al (2005): Linking out-of-body experience and self processing to mental own-body imagery at the temporoparietal junction. Journal of Neuroscience 25, 550-557. ↩︎
5. H-D Park & O Blanke (2019): Coupling inner and outer body for self-consciousness. Trends in Cognitive Sciences 23, P377-388. ↩︎
6. S Arzy et al (2006): Induction of an illusory shadow person. Nature 443, 287. ↩︎
7. D Azzalini et al (2019): Visceral signals shape brain dynamics and cognition. Trends in Cognitive Sciences 23, 488–509;
   G Northoff & F Bermphol (2004): Cortical midline structures and the self. Trends in Cognitive Sciences 8, 102–107. ↩︎
8. S Mullan & W Penfield (1959): Illusions of comparative interpretation and emotion; production by epileptic discharge and by electrical stimulation in the temporal cortex. AMA Archives of Neurology and Psychiatry 81, 269–284. ↩︎
9. D Denton (2006): The Primordial Emotions: The Dawning of Consciousness . Oxford University Press. ↩︎
10. D Azzalini et al (2019): Visceral signals shape brain dynamics and cognition. Trends in Cognitive Sciences 23, 488-509.  ↩︎