Thursday, April 16, 2009

A Testament to the Flexibility of the Human Mind

I'm sure you've heard that humans have five senses: sight, hearing, touch, taste and smell. But we actually have far more senses than that. The canonical list doesn't include equilibrioception-- our sense of balance-- the result of fluid sloshing around in the inner ear. It also doesn't include proprioception, the ability to detect the position of our limbs using nerve endings in our tendons and muscles.

Furthermore, the sense of touch is actually several different senses, each detected and transmitted by its own special type of neuron. The sense of touch includes vibration sense, pressure sense, heat sense, cold sense and pain sense. The sense of smell can be divided into roughly 400 senses in humans, each one tuned in to a different class of airborne molecules. Vision can be divided into cells maximally responsive to four different wavelengths of light.
I could go on but the rest are less exciting.

This brings me to what I really want to write about, the development (or perhaps refinement) of a new human sense: echolocation. Echolocation is the ability to gather sensory information about your surroundings by bouncing sounds off of objects and listening to the echo that returns. It's what bats use to hunt in the dark, and dolphins use to navigate muddy water and find food under the sand.
There are a number of blind people who have developed the ability to use clicking sounds to "see" their surroundings, and it's remarkably effective. This represents a new use of the human mind, or at least a refinement of a rudimentary sense. Here are a few links if you'd like to watch/read more about it:

Human echolocation- Wikipedia
Daniel Kish- You Tube
The boy who sees without eyes- You Tube


Robert Andrew Brown said...

Thanks for posting Stephan

Very humbling and compulsive viewing

Bryan - oz4caster said...

Fascinating and thought provoking as usual Stephan.

More thoughts on vision: stereo perception of distance and the ability of the mind to fill in the blanks, so to speak, which sometimes leads to illusions.


Anonymous said...

Wow that is amazing. Are you familiar with Sandra Blakeslee's book called The Body has a Mind of its Own? Its about the role of proprioception and body maps in a number of contexts. In case anyone is interested, I worked some of the info into a blog post on proprioception here:

Robert McLeod said...

Is this the area of your Ph.D. research or something else?

Aaron Blaisdell said...

And don't forget the remarkable plasticity of the human brain, such as shown in the seminal work by Bach-y-rita.

Stan Bleszynski said...

A friend of mine worked once on, and developed special ultrasonic "glasses" that allowed blind to see by hearing. They were miniature sonars head-worn, that down-converted ultrasound into audible. He worked with many blind students, some of them - those that were blind from birth had mastered a sense of echolocation. A student would come into a room, he/she would shout a sharp sound or just clap his hands and then just walk in aware exactly where each piece of furniture was, able to grab a chair and sit down on his own.

Stan (Heretic)


The most interesting experience with various form of sensory perception comes while experimenting with coordinate remote viewing. Worth trying!

Stephan Guyenet said...


I haven't heard of that book.


I work on neurodegenerative disease and aging.


That is really wild.

homertobias said...

Neurodegenerative disease and aging. Great! Good future there. Just beginning to open up. With all the baby boomers hitting "that age" and struggling to stay younger you'll have a great future.
Do you have a thesis? Do you work with animals in someone's lab? I worry that with all the wonderful attention you give to this blog that your PHD might suffer.

Nick said...

Anyone who has interest in learning more about the plasticity of the brain and incredible stories about how neurons that 'fire together, wire together' to achieve astounding change and repair in many people should check out a fascinating book by Norman Doidge called 'The Brain that Changes Itself', with great descriptions of Bach-y-rita's ground breaking work included.

The book attempts to describe, for example, why a blind person is able to develop an uncanny sense of space and hearing due to the brain rewiring itself. Also, get blown away by a girl who describes what it is like to have only half a brain! Just an incredible journey into the frontiers of brain science.

Anna said...

"I work on neurodegenerative disease and aging."

Stephan, do you ever run across my husband's work in basic research? Apoptosis is one of his areas - Guy Salvesen @ Burnham Institute for Medical Research).

Anna said...

Sorry, I typed too fast and thought too little. I should have said "my husband's lab", as he certainly directs a hard-working and bright team of young researchers who do most if not all of the actual bench work that makes publishing possible.

Stephan Guyenet said...


I do have a thesis. It's a mixture between studying a neurodegenerative disease called SCA7 and the mechanisms of aging.


I had not come across your husband's research. I've only been studying aging in earnest for a year and a half, so there are a lot of corners in the field I'm not familiar with. I mostly read the yeast aging lit, and some mouse and roundworm.

Anna said...


When you say roundworm, do you mean c. elegans?

Unknown said...

According to a book I've been reading called Brain Rules by Dr. John Medina, vision is usually our most powerful sense because it's the primary way we've detected food and threats in the environment. Perhaps we aquired this type of neuroplasticity-aided adaptation through evolution as a "back up" for the loss of vision or other primary senses and brain functions?

Stephan Guyenet said...




Maybe so. People who lose their sight report that their other senses improve. In animals, if you remove part of one sense, the other parts invade that part of the cortex and use it. It's pretty amazing and speaks to the flexibility of the cortex. The senses are in constant competition for brain room; use it or lose it.