A Healthy Brain Knows Where You Are the Whole Time You’re Conscious.
Somewhere in our heads, a constant mental narrative that tells us where we are, if we,re upside down, where our physical self stops and the surrounding world begins. Body awareness, also called the ‘body schema’ or ‘corporeal awareness’, is essential for a host of functions that don’t get much attention – everything from knowing we’re laying down to recognizing our 10-year-old selves in a photograph. “Brains like that stability because it would be very confusing through life otherwise,” is how Dr Perminder Sachdev, neuropsychiatrist and author of The Yipping Tiger, describes body awareness.
According to recent studies, it’s something we might be born with. Maria Laura Filippetti, of the University of London’s Centre for Brain and Cognitive Development, showed rudimentary body awareness in babies by stroking their cheeks with soft brushes. When her tiny subjects saw videos of other babies’ faces being stroked with other brushes, they took more notice. The researchers’ conclusion was that the baby understood how the experience in the video was the same as its own – something it would need an intact sense of self to appreciate.
As we grow, our corporeal awareness becomes stronger and more adaptable. Interestingly, back in 1997, Giovanni Berlucchi and Salvatore Aglioti, neurologists at the University of Verona, published a paper called, The Body in the Brain: Neural Bases of Corporeal Awareness. In it they stated that ‘The body schema can be extended to include non-corporeal objects that bear a systematic relation to the body itself, such as clothes, ornaments and tools.’
Illusions of Certainty
Assuming we’re healthy, our physical experience may make our body awareness feel unshakable but it’s actually very fluid. For one, it’s been discovered that stimulation of certain facial areas can evoke phantom limb sensations, and the location that elicits them can change over time. Body awareness, as it turns out, is a complicated process with a lot of moving parts.
Psychological and/or physical damage, such as a stroke or limb loss, can drastically affect our body schema. “The brain’s malleable,” says Sachdev. “With certain illusions of visual input you can trick the body to feel differently. That’s because of the plasticity of the brain.” Even those born with missing limbs can suffer from phantom limb syndrome suggesting that there’s, what he calls, a ‘genetic aspect to body concept’.
Furthermore, Berlucchi and Aglioti’s paper reports on experiments that use electrical stimulation on a brain region called the insula, which cause ‘illusions of changes in body position and feelings of being outside one’s body.’ Some of the illusions Sachdev refers to include groundbreaking work by neuroscientist Vilayanur Ramachandran of UC San Diego.
In one experiment, a subject sitting at a table has one arm enclosed in a box with a mirror on the side, meaning it reflects what the other are is doing. The brain can quickly shift the sensation of the hidden arm to the mirror image, prompting confusion and embarrassed giggles when it doesn’t do what the subject expects.
Such experiments have even been used successfully to cure phantom limb syndrome in some patients in Ramachandran’s lab. When the mirrors-and-boxes system tricks the brain into thinking there’s actually a limb there when there really isn’t, phantom limb symptoms disappear in some patients like magic, as if the brain finally accepts the limb is gone.
What’s more, researchers at Sweden’s Karolinska Institutet created phantom limb sensations in subjects who had all of their limbs intact, giving them imaginary supernumerary parts. You can also quite easily use mirrors to trick the brain into thinking a fake hand belongs to it. For example: by pricking it with a pin, the subject may feel some of the pain.
The mind has to make constant adjustments about where the body is and what its various parts are doing, so of course body schemas can,t be too rigid. When you ride a bike, for example, it becomes part of your body schema. You manipulate it semi-consciously just like you do your own muscles. But when you dismount the bike, it turns into just another discrete object that has nothing to do with your functioning.
Dr Sachdev says that the fluid nature of body awareness is constructed from two different directions. What he refers to as a ‘bottom up’ body schema has to do with the input we receive from our senses, such as resistance from the weight of our limbs and even sensations inside some of our organs that are all processed by different brain regions.
“But I think there’s a body concept which is top down too,” he says, “a kind of psychological or mental concept.” Filtered completely through our current mental state, it,s an entirely emotional percept that makes our body awareness a roiling knot of mental health, physical sensation, mood and psychology.
When the System Breaks
But it can go disastrously wrong. Phantom limb syndrome exists because the brain has a long-standing mental map for a body part that suddenly stops sending input, or as professor Ronald Melzack calls it, ‘the persisting activity of neuromatrix components’. The neural processing that used to deal with it doesn’t cease to exist along with the missing limb, and the illusion of persisting activity might result in phantom limb syndrome.
Berlucchi and Aglioti even wondered if the brain might impart functional characteristics of the missing limb to the remaining stump, causing an ongoing nervous response.
Problems with body awareness create a broad range of fantastical-sounding afflictions like anosognosia, somatoparaphrenia, hemiasomatoagnosia and dysmorphophobia. These are unimaginable conditions for those who have their body schema intact. For example, a 73-year-old woman whose left arm was paralyzed after a stroke showed total unawareness of her immobility, to the extent she believed her arm belonged to someone else. Extreme cases can adversely affect the afflicted persons quality of life; they may have trouble holding down jobs and/or maintaining relationships.
Most of us have a self-questioning mechanism that monitors our experience. A skewed body schema, however, may disconnect others from this built-in ‘reality censor’, says Dr Sachdev. Think of those suffering from schizophrenia as having phantom voices in their heads. “Normally we delimit ourselves, we know where our body stops and the rest of the world begins. But some patients with schizophrenia lose that boundary. There’s certainly a disturbance of body schema to some extent.”
In The Body in the Brain: Neural Bases of Corporeal Awareness, the authors add that body-centered delusions, such as underestimation of the size of body parts, are often observed in major psychiatric illnesses. They state that, ‘Visual, auditory and olfactory phantom sensations have been reported after differentiation of the corresponding sense organs.’
Thankfully though, some body schema problems are more benign. Difficulties understanding the difference between the self and someone other, remind many researchers of symptoms caused by an autism spectrum disorder. After Maria Filippetti completed her newborn body awareness experiment, she stated that, “Our findings may also be relevant to the investigation of early predictors of developmental disorders in infants, such as autism, where an impairment in the discrimination of self/other is believed to be present.”
But what about all of the ‘out of body’ experiences? We’ve observed relevant brain regions that deal with the body’s position in space, light up in PET scans. If they fire up when we’re not going anywhere, might that give us the illusion of floating away from our hospital beds or down tunnels of light? In a study conducted at Vanderbilt University, one lifelong schizophrenia sufferer routinely had out of body experiences, including several in the lab.
Cause and Treatment
Because every thought, action and emotion, is essentially neurological in nature, anything that affects the brain can cause breakdowns in body awareness – from stroke-induced brain lesions and tumors to invasive surgery.
“The parietal lobe in particular seems to be important because it’s where all the sensations are coming together,” says Dr Sachdev. “There’s also the insula, which is the meeting of the parietal, frontal and temporal lobes and which receives a lot of sensory and emotional input.” This means that psychiatric disorders are another major cause of body awareness afflictions.
Sachdev explains how psychotropic drugs, electrical manipulation of brain regions, caloric stimulation, or even psychoanalysis are all means to the same end, that is, change the physical structure of your brain to affect its function and content.
“We don’t know how some treatments do it but in many cases they’re reversing some of these disturbances,” he says. “When it comes to anorexia nervosa, bringing sufferers to a normal body weight sometimes helps with the body schema disturbance. You can change neural processes to produce mental change or you can change mental processes to produce neural change.”
So appreciate your body schema while it’s intact – you never know when you might wake up not quite feeling yourself.