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Anosognosia

RELATED STORIES

Michael Merzenich and stroke patients
Gerald Edelman Scientist
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There is one more very important point to make, and that is that in neural modeling above all, you can't just do many models abstractly and expect to get deep answers and that's because of the following: the brain is embodied and the body is embedded. What do I mean by that? I mean... well, let's take the example I love the most – for example, as a violinist... when you play the violin, it's a rather unnatural position; your elbow's all the way over here and the other one has got to be, at least according to the Russian schools, that you move in a plane and you don't lift your shoulder too high or knock your elbow down too low. When you look at that you... you have to convey that there's... there's a considerable problem and the problem is this: that if I, for instance, had an octopus tentacle or a squid tentacle that was extremely good at certain kinds of things, I could never play the violin, no matter what. And the reason is I have no joints, and if I want to play so-called spiccato or staccato and I have to have this kind of almost digital change in emphasis on the bow, having something without a joint will never work. Well, if I did put one in, my brain would change. And that's an important point that I want to mention.

And the reason I want to mention it is the work of Michael Merzenich at the University of California, San Francisco, was the first piece of work that I felt configured a real support for the idea of neural Darwinism. What he showed was that if he had a monkey tapping, say on a table, and he measured the response of neurons in the part of the brain called the somatosensory cortex, which is responsible for getting the messages about tapping and touch, he found an astonishing thing; namely that if he tapped on different fingers it would be a map that was individual for that monkey. So digit one would have this map for the smooth side of the hand, digit two another, third, etc, and you could make that map and no two monkeys were alike. But if, in fact, you had the monkey tap a lot, say with one finger, that the map responding to that finger would take other neurons away from the ones that are neighboring. Indeed, some would even take so-called face neurons away and make them hand neurons. And when you cut the nerve to the hand, one nerve – the so-called median nerve, that serves this part of the thumb and the first part of this, this finger and the first part of this finger on the smooth side – when you cut that the whole system rearranges its borders and smoothly. Well, the only way you can really explain that result is through something like neural Darwinism, that these neuronal groups are competing to grab hold of other neurons in such a way as to make a new kind of map. And that was a very satisfactory finding. Indeed, it's been reported ever since that violinists have an incredible large map for their left hand.

And this all fits this notion of neural Darwinism very well. So the brain is altered by what kind of bodily reactions you have and, indeed, if I wanted to get very much more severe about it... I'll say it another way. It is so strong that even cognitively a patient will react differently to what happens in his body with his brain. Perhaps I should use that example. There is a disease, in a field called neuropsychology. Neuropsychology studies in large measure things that happen to you for example when you have a stroke. Now if you have a stroke on the right side of your brain... in the part of your brain called the parietal cortex, right over here above your ear, a little more posterior, you have what they call hemineglect: you do not see one half of the opposite part of the world. So if it's on your right cortex, where it usually is, you don't see the left half. So when you look at a clock you see from six to 12 or from 12 to six, either way depending on how you're looking at it, and not the other side.

US biologist Gerald Edelman (1929-2014) successfully constructed a precise model of an antibody, a protein used by the body to neutralise harmful bacteria or viruses and it was this work that won him the Nobel Prize in Physiology or Medicine in 1972 jointly with Rodney R Porter. He then turned his attention to neuroscience, focusing on neural Darwinism, an influential theory of brain function.

Listeners: Ralph J. Greenspan

Dr. Greenspan has worked on the genetic and neurobiological basis of behavior in fruit flies (Drosophila melanogaster) almost since the inception of the field, studying with one of its founders, Jeffery Hall, at Brandeis University in Massachusetts, where he received his Ph.D. in biology in 1979. He subsequently taught and conducted research at Princeton University and New York University where he ran the W.M. Keck Laboratory of Molecular Neurobiology, relocating to San Diego in 1997 to become a Senior Fellow in Experimental Neurobiology at The Neurosciences Institute. Dr. Greenspan’s research accomplishments include studies of physiological and behavioral consequences of mutations in a neurotransmitter system affecting one of the brain's principal chemical signals, studies making highly localized genetic alterations in the nervous system to alter behavior, molecular identification of genes causing naturally occurring variation in behavior, and the demonstration that the fly has sleep-like and attention-like behavior similar to that of mammals. Dr. Greenspan has been awarded fellowships from the Helen Hay Whitney Foundation, the Searle Scholars Program, the McKnight Foundation, the Sloan Foundation and the Klingenstein Foundation. In addition to authoring research papers in journals such as "Science", "Nature", "Cell", "Neuron", and "Current Biology", he is also author of an article on the subject of genes and behavior for "Scientific American" and several books, including "Genetic Neurobiology" with Jeffrey Hall and William Harris, "Flexibility and Constraint in Behavioral Systems" with C.P. Kyriacou, and "Fly Pushing: The Theory and Practice of Drosophila Genetics", which has become a standard work in all fruit fly laboratories.

Tags: Michael Merzenich

Duration: 4 minutes, 18 seconds

Date story recorded: July 2005

Date story went live: 24 January 2008