Somewhere in our heads, a constant mental narrative tells us where we are, if we’re upside down, where our physical self stops and where 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 to go through life otherwise,” explains Dr. Perminder Sachdev, neuropsychiatrist and author of “The Yipping Tiger and Other Tales from the Neuropsychiatric Clinic.”
According to recent studies, it’s something we might be born with. Dr. 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 babies’ faces being stroked with similar brushes, they took more notice. The researcher’s conclusion was that the babies understood how the experience in the video was the same as their own.
As we grow, our corporeal awareness becomes stronger and more adaptable. Interestingly, Drs. 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 noncorporeal 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 thing, 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 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 a “genetic aspect to body concept,” Sachdev says. 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 Dr. Vilayanur S. Ramachandran of UC San Diego.
In an experiment, a subject sitting at a table had one arm enclosed in a box with a mirror attached on the side, meaning it reflected what the other arm was doing. The mirror-and-box system tricked the brain into thinking there was actually a limb there when there really wasn’t. Such studies have even been successfully used to cure phantom limb syndrome in some of Ramachandran’s patients. Furthermore, researchers at Sweden’s Karolinska Institutet created phantom limb sensations in subjects who had all of their limbs intact, in effect giving them imaginary supernumerary parts.
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 semiconsciously 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.
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
Phantom limb syndrome exists because the brain has a long-standing mental map for a body part that suddenly stops sending input or, as Dr. 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, hemiasomatognosia, 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 left arm belonged to someone else. Extreme cases can adversely affect the afflicted person’s quality of life; they may have trouble holding down jobs and/or maintaining relationships.