Our senses of self are tricky things to pin down. We all appear to possess intuitive notions of our own identities. We're all sure there's something — whether it be our personalities, our principles, our abilities or our ambitions — that sets us apart. But our senses of self arise out of an assortment of cognitive processes, which, if altered, can change our perceptions of ourselves and our worlds.
Take your awareness of your own body, for instance. A significant part of your sense of self is physical, with your consciousness being tethered to the inside of your brain. But what happens when your center of consciousness is untethered, triggering what's commonly called an out-of-body experience?
Experts have asked this question since the 1800s, but neuroscientists are only now starting to unravel how these experiences come to bear.
What Are Out-Of-Body Experiences?
People often describe out-of-body experiences as a sense of weightlessness, or drifting, where they might see their body from above.
These experiences tend to occur when we transition between different states of consciousness — when we go under anesthesia, when we wake up from sleep or even when we have a near-death-experience.
Read More: Is Mental Time Travel Good For Us?
What Causes Out-Of-Body Experiences?
Out-of-body experiences are triggered by the stimulation of specific brain regions, such as the anterior precuneus (aPCu), which integrates sensory information related to the body, its vision and its balance and spatial orientation.
In a recent study, Josef Parvizi, a neuroscientist from Stanford University, wanted to know what regions of the brain were involved in triggering out-of-body experiences, hoping it would provide new insights into the complex construction of our senses of self.
Parvizi and his team worked with nine epilepsy patients who had electrodes inserted into their brains as part of their treatment for severe seizures. With their consent, the researchers stimulated regions of the patients' brains with electrical pulses and asked whether the patients experienced self-dissociation, or out-of-body experiences, as a result. Their findings were published in the journal Neuron in August 2023.
Isolating Out-Of-Body Experiences in the Brain
"Once we discovered the specific region whose stimulation caused self-dissociation, we then investigated what other brain areas (or so-called networks) are connected with this region," says Parvizi.
"We did this in two ways," he adds. "We looked at the blood flow correlations between this region and the rest of the brain. If other regions are working with this hub region of interest, then their blood flow must be coordinated. In addition, we also delivered single pulses of electricity to the hub region and watched the evoked responses in certain other brain areas. This told us where the hub region is sending information."
Their results pointed them towards the anterior precuneus, a region of the brain associated with somatosensory, or body-related, information. The aPCu and its allied areas process a complex concoction of multi-sensory stimuli, combining sensations such as pressure, pain and warmth with visual and vestibular information, which relates to balance, stability and spatial orientation. Beyond that, the aPCu is also connected to the posterior cingulate cortex, which is believed to be involved in the performance of mental time travel.
Triggering Out-Of-Body Experiences in the Brain
As a result of these findings, the team concluded that the spatial sense of self involves the integration of multiple brain regions and sensory modalities. Yet it only took seconds for patients to report distortions in their sense of space and their locus of consciousness after they received the pulses of electricity, and that surprised the researchers.
"Although we have always known that our sense of self is constructed from interactions with the environment, and through our body, this process can be much quicker than we thought," says Dian Lyu, a postdoctoral fellow who co-authored the study.
"It does not take days or hours," she adds, "but may happen in seconds, or possibly within a second. By only 2 to 4 seconds of stimulation in our study, it was already possible to make people experience self-dissociation."
What Influences Our Sense of Self?
Our sense of self seems to emerge from a number of cognitive processes, some more abstract than others. One of these processes is our ability to travel through time in our minds. When we remember the past and imagine the future, we solidify our sense that we remain ourselves over time. Another one of these processes is our ability to exercise agency. When we make choices, we strengthen our perception that we are active causal agents in our own lives.
And yet another part of your notion of selfhood is your ability to situate yourself spatially, creating the sense that your consciousness is located inside your body.
Of course, all of these aspects of selfhood can be manipulated or altered. People can experience memory loss or a lack of control or agency over their lives. People can also encounter moments where their spatial sense of self separates from their usual frame of reference.
Read More: The Multi-Faceted Nature of Selfhood
Are Out-Of-Body Experiences Real?
While out-of-body experiences are real in the sense that people genuinely report having them, their interpretations and underlying causes are a subject of debate.
Previous research on out-of-body experiences has pointed to conditions where an individual's intake of visual information might be misaligned with their intake of vestibular information. Groups of individuals with vestibular conditions, such as benign paroxysmal positional vertigo (BPPV), are more likely to experience out-of-body experiences.
Parvizi says the new research is in line with previous work but cautions that the causal relationship between the intake of sensory information (whether it be somatosensory, visual or vestibular) and the integration of that information to form a sense of the body's position in space is not yet clear.
"Disrupted processing in any of the sensory domains may cause a misplaced body schema, and the body schema will, in turn, alter how the sensory inputs are represented," Parvizi says. "The causal relationship may be the other way around. When the sensory inputs are correctly in place, but if we disrupt the body schema (which we believe is what we did in our study) ... then the sensation become misaligned."
Making Sense of the Senses
In the typical, transitional contexts in which out-of-body experiences occur, people's brains are working in overdrive to integrate sensory information that places their sense of self somewhere in space. But since the bi-directional relationship between sensory input and our brain's knowledge of where we are is likely disrupted in these scenarios, it shouldn’t be surprising that we might experience distortions in where we experience our consciousness.
Studies like the one conducted by Parvizi and his colleagues help researchers identify the neural underpinnings of our sense of self. In reality, there's no "seat" of the self in the brain, but rather a complex network of regions and functions that collaborate to create the multi-dimensional aspects of what we experience in our everyday lives.