Visual Distortion and Pain
A fair bit of research is focused on the issue of chronic pain, and for good reason. People who suffer chronic pain, which is usually defined as pain that persists or recurs for more than three months, are often unable to focus or live normal lives, their capacity to do everyday things disrupted by continuous or sporadically reemergent bouts of alarming neuralgia or back pain or migraines or some other thoroughly disruptive internal signal that something’s wrong.
Consequently, people with chronic pain are more likely to develop secondary issues related to that primary concern, including chronic stress and anxiety, sleep deprivation, a higher risk for metabolic issues and heart attack, and even some types of brain damage.
Anything that can help folks suffering from chronic pain is worth a look, then, and if a potential solution (or even minor salve) doesn’t come with its own downsides (like opioid addiction), all the better.
This is part of how researchers stumbled upon the concept of perceptual distortion as a possible means of helping ease chronic pain in some sufferers.
Probably the most well-known example of this is a trick developed to help reduce the intensity of (and in some cases, completely eliminate) the phantom pain suffered by those who have lost a limb, but whose nerves tell them the limb is still attached, and that it’s clenched tightly, being stabbed, or going through some other kind of pain-causing experience.
If the patient has lost a hand, it’s sometimes possible to use a mirror to make it look like they still have their missing hand so that the patient’s brain registers it as being real, and then to have them unclench the hand, or in some other manner ease the phantom pain, so that when the mirror is removed, the pain has also dissipated.
Similar techniques have been used in studies that show our brains can be tricked into treating body parts on what amount to out-of-proportion mannequins (somatosensory homunculus) as our own body parts when different sensations are triggered, while seeming causes of those sensations are applied to the model. The scale of the body parts on the model seem to sometimes influence the degree to which we feel these effects, so using this technique on a model with larger hands can result in more powerful mirrored sensory experiences, while using one with smaller hands will tend to result in less powerful experiences.
A study from 2008 used a similar theory to determine whether distorting the perceptual size of our own body parts might influence our experience of pain in those body parts.
The researchers used binoculars to either increase or decrease the size of a hand in which the subject is experiencing chronic pain, to see if making that hand look larger or smaller might influence the amount of pain they perceive, and the amount of swelling experienced in the hand when they work through swelling-inducing movements.
They found that the patients experienced more intense pain and swelling when viewing their hands through the magnifying side of the binoculars (making their hands look bigger and closer), and the opposite was true when viewing them through the other side, their hands looking smaller and further away.
Both subjectively and objectively (their sense of how intense the pain was, and their body’s response to the movements, based on the amount of swelling experienced), the nature of their chronic pain changed based purely on how big and close, or small and far away their hands looked to them while working through these exercises.
This is interesting because it suggests our body image (our sense of what our bodies look like, and conception of where they are in space) might impact both the sensory information we perceive through our body parts, but also our body’s response to things that seem alarming—even to the point of adjusting its response to those alarming things.
This could, in turn, lead to more therapies that are predicated on adjusting a patient’s body image, which might be useful alongside physical therapy and pharmaceutical interventions.