Tuesday, April 13, 2010

The plastic brain: a theory of human experience

Norman Doidge has written a book that encapsulates the latest research in neuroplasticity and delivers it to the curious mind in an intellectually stimulating and satisfying read. The Brain that Changes Itself: Stories of personal triumph from the frontiers of brain science, is a book that had me raving to family and friends after each chapter. I could only put it down to ponder the significance of the subject matter to human society before reading on.  I want to take this opportunity to highlight a few titbits that stuck with me.

Early on, we find out that our brains can use almost any input as a sense. A lady who has lost her sense of balance (her vestibular function), and couldn’t stand straight and felt dizzy as soon as she turned her head or her focus of vision. Her brain learnt to take the electronic impulses of a plate under her tongue, power by a gyroscope, as a new vestibular system, and she learnt to balance again. In fact, there was a residual effect even after the device was removed. She learnt to balance again without the sensory input from our balance organ.

Sensory input, including pain, is not a one way street from the skin, nose, tongue or ears, but a two way street that also leads from the brain to the organs. That’s why phantom pain of amputated limbs can still persist. But can you see pain?

One of researchers we meet, Vilayanur Subramanian Rmachandran, demonstrates that we can. He primes the brain to associate the visual input of light touches and taps on a tabletop, with touch input onto our hands. The subject puts one hand under the tabletop and the researcher taps the table top in sync with tapping of the subject’s hand under the table. When the tapping or stroking of the tabletop moves to the left, the stroking of the hand also moves to the left. He can trains a subjects brain to associate the surface of the tabletop with the surface of their hand. Soon, the subject can ‘feel’ the touch on the tabletop without the hand being touched at all. And the result of his intensive experiments are very interesting.

Ramachandran has wired subjects to a galvanic skin response meter that measures stress responses during the table experiment. After stroking the tabletop and a patients hand under the table until his body image included the tabletop, he would pull out a hammer and bash the tabletop. The subjects stress response went through the roof, just as if Ramachandran had smashed the subject’s actual hand.

The underlying plasticity theory presented in the book explains many other psychological and social theories. Is encompasses so much existing knowledge you wonder why we haven’t thought of it before (we had thought of it, just couldn’t provide evidence because for so long you could only examine the brains of dead people). Plasticity explains why our childhood experiences cement our adult personalities, and how learning actually occurs in the brain – why it take so much repetition to learn a task or some facts, then once they are learned, you find it hard to forget. For parents there are plenty of insights into childhood behavioural patterns, and how to break or reinforce them, and insights into why toddlers are sponges for information. The saying “Give me the boy for seven years and I’ll give you the man” has a neuroplastic explanation.

You also gain insights across such broad psychological topics as pornography addiction, and encounter the 'plastic paradox', which explains why we become so habituated even though out brain is able to fundamentally restucture itself. 

After reading this book you may become absorbed with amazing feats of the human brain, like echo location (and an interesting case here), and blind people seeing with their tongue through the assistance of video inputs.

This book with radically change your understanding of the world.

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