Ferreting out neurology info

Factual Questions
1

Yesterday’s New York Times had an article about an experiment in the April 20 issue of Nature magazine. The Times report is here"]http://www.nytimes.com/library/national/science/042500sci-animal-ferret.html]here (free registration required); the Nature site is subscription-only.

The gist of the report is that neurologists rewired the brains of infant ferrets such that the optic nerves fed into the portion of the brain normally devoted to processing auditory input. The auditory centers developed much like one would expect the optic centers to under normal circumstances and the ferrets could see. (Ferrets were chosen because their brains are relatively undeveloped at birth).

Ethicists, take the argument to GD, please.

Others, what is the significance of this finding? Combined with new knowledge of adult brain regeneration in humans, are we nearing important breakthroughs in neurology? Does this have larger implications in the overall nature/nurture debate? Or was it all just a pretty cool experiment?

2

A layman’s opinion:

It means if you want to get smarter, you could go to a surgeon, and they would open up your head, throw another brain in, and sew you back. Then you’d be twice as intelligent.

3

In that case, sign me up. Jeopardy tryouts are coming up.

Try not to have a good time…this is supposed to be educational.
-Charles Schulz

4

The findings would tend to indicate that, undeveloped brain cells will specialize based on the nerve input they receive.

How does this help mankind?

Dunno.

How does this help me score with chicks?

Dunno

Am I supposed to believe that all this rain was suspended in mid-air until moments ago?

5

manhattan, are you sure this shouldn’t be in GD? :slight_smile:

Anyway, I don’t have an opinion as of yet, but I thought you might find the following information about cats interesting and relevant to the above article. This information has been around for quite a while, as the book I’m quoting from was published in 1991:

From Feline Husbandry: Diseases and Management in the Multiple-Cat Environment, by Niels C. Pedersen, DVM, PhD, published by American Veterinary Publications. pp 86 - 87

"Albino mammals completely lack melanin pigment; hence, their eyes are pink or red and the coat white. They also have a misrouting of the visual pathway from the retina to the brain.(My bold) the anomaly has been detected in albinos of all species so far examined, including Syrian hamsters, guinea pigs, rabbits, mice, rats, ferrets, mink and one species of monkey. The visual pathway is affected in cats carrying either the albino (c) or Siamese (c(s)) allele, but not the Burmese (c(b)) allele.

The ganglion axons from the retinal cells of the eye normally travel to the lateral geniculate nucleus of the thalamus. This nucleus is sited in each side of the brain. Each eye contributes fibers to defined layers of the lateral geniculate nuclei. A disproportionate number of the fibers in the Siamese cat . . . crosses to the lateral geniculate nucleus on the side opposite to the eye. The lateral geniculate nuclei are incorrectly innervated in reverse order. the cat’s brain probably does not receive a distorted picture, however.

Elegant experiments suggest the the visual field is compensated by either of 2 methods. The most direct is apparent suppression of the abnormal information when it reaches the visual cortex (the “mid-western pattern”). The other compensation method involves rearrangement of information inputs to recreate a normal visual field (the “Boston pattern”). The 2 methods of compensation may not be absolute, but rather part of a continuum. The method of compensation may depend upon the extent of the erroneous crossover of ganglions. Misrouting is present from the earliest prenatal stages of development of the ganglion pathway and arises at the optic chiasm. Misrouting is present from the earliest prenatal stages of development of the ganglion pathway and arises at the optic chiasm. Misrouting may interfere with normal binocular depth perception and is responsible for the convergent squint to which Siamese are particularly prone.

The Siamese allele . . . falls short of complete albinism, but the complete albino alele . . . has recently been recognized. Examination of the visual pathway in albinos reveals misrouting to be much greater than in Siamese. A much higher proportion of the ganglion axons crosses over to the opposite lateral geniculate nucleus. As a consequence, organization of the visual field in the cortex differs from that observed for Siamese. The albino allele is completely recessive to full color (C) as regards eye and coat color, but not for misrouting of ganglion axons. Heterozygous Cc albinos or Siamese have similar misrouting, but less extreme." (Ellipses used in place of some difficult-to-reproduce genetic notation.)

In other words, mammals that are albino, albino series mutations, or who carry a recessive albino/albino series gene have differently wired visual pathways - but still apparently see and function quite well. Hmm, some of this info might have inspired the ferret re-wiring experiment.

Brains are certainly versatile organs.

God is love. Love is blind. Ray Charles is blind. Therefore, Ray Charles is God.

6

It’s not only young brains that can adapt. I read a book called (I think) The Brain Book 3 or 4 years ago. I don’t remember the author’s name, but the book was based on a series of articles he wrote for one of the Chicago newspapers.

He describes an experiment in which adult monkeys had the nerves to their hands cut. After a while, the parts of the brain that had controlled the fingers took over new functions. Young brains are even more adaptable, because they contain high levels of “Nerve Growth Factor.” In the laboratory, ordinary cells (not brains cells) bathed in NGF take on some of the characteristics of brain cells. Such cells have even been implanted in the brains of Parkinson’s patients experimentally.

Older brains have much less NGF than young ones, but direct injection of NGF into the brain can probably permit a similar revitalization. NGF cannot pass the blood-brain barrier, so there’s not going to be a pill.

I have also read (in the same book?) of several cases where the underlying cause of deafness or blindness in adults was corrected by surgery, but in which the patient still could not see or hear. Similar operations in children are more often successful, presumably because the high levels of NGF allows their brains to develop visual and auditory centers in the brain where none was before.

As if that weren’t enough, NGF may also be a Cure for Baldness.

Work is the curse of the drinking classes. (Oscar Wilde)