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 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, 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.
Most of us have a self-questioning mechanism that monitors our experiences. A skewed body schema, however, may disconnect others from this built-in “reality censor,” says 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, “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 Filippetti completed her newborn body-awareness experiment, she stated, “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 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 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 and even psychoanalysis are all means to the same end — changing the physical structure of the 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 feeling not quite like yourself.
This article was originally published in the Spring 2014 issue of Brain World Magazine.