Sensory compensation: Re-train your brain

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This blog is a first for me, as it is the first blog I have written in collaboration with another author. The idea for this blog, and the research that I have used to provide the content has come from good friend Vicky Perry. The discussion started from Vicky’s experiences of physiotherapy, and some of the techniques used to aid her recovery from a knee injury (more on this later). Specifically, I was interested in the concept of sensory compensation – the ability of the senses to compensate where one or more of the senses is restricted in its ability to function. Vicky suggested that if I found the subject matter interesting, that it may be a good idea to write a blog about it, and that she would be more than willing to help me research and write it.

And so here is the first (and hopefully not the last) joint collaboration between myself and Vicky (pictured below) in writing a blog.

I’ve been aware of the idea of how the body will compensate for the lack of a sense by heightening the remaining ones. For example, most of us will be aware of the fact that a person who has restricted eyesight will have their other senses raised to compensate for the missing one. This makes perfect sense. The body is adapting to try to reduce the effects of the missing sense(s) by raising the ones that remain. It is also a superb example of what a wonderful piece of machinery the body is, that it can so quickly adapt so that it is able to extract as much information from the environment as possible.

What I didn’t realise was that this same mechanism doesn’t just work over the long term, where the body has time to adapt over a longer period of time, but it can take effect almost immediately. For example, it can be found by simply blindfolding someone and removing the eyesight. Very quickly, the body compensates by heightening the remaining senses.

This phenomenon has been well documented in the article Overcoming Blindness: Other senses Compensate in Just 10 Minutes. One of the most striking examples of this phenomenon is the following account of blind cyclists:

“Four bikers headed off down a street in Southern California, safely navigating through traffic and past parked cars, and turned onto a narrow bike path leading up a steep hillside. None of them veered off the dirt path, and all safely avoided boulders along the way, always conscious of their surroundings and any possible obstacles.” Extracted from the above article.

Three of the four cyclists were blind, but could navigate equally as well as the sighted cyclist. Using the same mechanism as bats do in a dark cave, they would use echolocation to navigate, using the sounds echoing back from the trees, rocks and other features as they cycled along. The article goes on to describe other extraordinary examples where the senses have compensated for a restricted one.

These examples have been documented by Professor Lawrence Rosenblum from the University of California, Riverside. He is a psychology professor with 25 years study under his belt. What is even more extraordinary than these accounts of breathtaking adaptations by the human body, is research that suggests that these adaptations can take effect very quickly. The human brain is capable of rewiring itself – albeit even if only temporarily – so that a person can continue to lead an enriched life, and is able to perceive the world as well as someone with the same sense(s) unrestricted.

To demonstrate this ability to quickly learn how to compensate for restricted vision, Lawrence Rosenblum conducted an experiment where a blindfolded person can learn to walk towards a wall and stop before hitting it. Here’s how it works, and you can try this for yourself. Make a sound, doesn’t really matter what it is, a hissing sound will suffice. As you walk blindfolded towards the wall, the sound changes depending on the distance between yourself and the wall. Walk towards the wall and you will begin to recognise how the pitch of the sound changes in relation to your distance from the wall. After around 10 minutes or so practice, you should be able to walk towards the wall without hitting it.

In a recent article in The Independent newspaper is the story of a musician who had suffered from a condition called hyperacusis. This is a disorder whereby the hearing becomes acutely sensitive to sound, often to the point of pain. The condition shows no physical symptoms, as there is no physical damage to the ear. Instead, the condition is brought about by the brain playing tricks on the ear, and causing the ear to become more sensitive to sound. In the case of the musician described in the newspaper article, he had become afraid of hearing loud sounds, and this had caused him to become anxious and stressed, which in turn caused his brain to produce a substance which increased his sensitivity to sound. Effectively, the more anxious he became, the worse his condition became. With no physical damage to his ears, this is another demonstration of how the brain can directly affect the senses.

There is naturally research that is critical of this phenomenon. The main grounds for this criticism is the distinction between having better senses, and using those senses more effectively. The account of the blind cyclists demonstrates the extraordinary degree to which this can be taken. Taking the criticisms of hearing, the spatial hearing of blind and sighted individuals were examined to test how well participants were able to tell the direction a sound was coming from. Although the blind participants did perform better than the sighted ones, the difference was only marginal. So this would seem to suggest that the blind participants were making better use of their hearing, and not that their hearing had become somehow improved.

Vicky herself was subjected to the phenomenon directly as part of her physiotherapy to recover from a knee injury sustained through running. Part of the final stage of the physiotherapy was to build core muscle strength, as well as to build the muscles in the knee itself. An effective way of doing this is to balance on the damaged leg to make the muscles and ligaments work harder to make a stable core. A further extension of this exercise is to balance on the damaged leg with your eyes closed. This is harder than it sounds. Her first attempt at this was barely 10 seconds. It is surprising just how much effect sight (or the loss of sight) can affect your balance. After practising for a week, Vicky was eventually able to balance on the one leg with her eyes closed for a full 60 seconds without wobbling. In effect, she had re-trained her brain to compensate for her temporary loss of sight. This is exactly what the studies by Lawrence Roseblum concluded.

In my mind there is little doubt that the body is capable of adapting to new circumstances. This is exactly what is explained by Darwinian natural selection. So although the newly acquired behaviours may not be inheritable, they exist nonetheless. The body is capable of all manner of amazing feats of self preservation. This is another example of just how amazing our bodies are, and how they can adapt to ensure we have the richest interaction with our environment.