Learning about learning
Yearning for learning
New neurons
Brains 'n sweat
Sprouting brain cells
Stem cells
The death of dogma
Until the last few years, neurologists who believed that new nerve cells appeared in brains of adult mammals were about as common as mint-green Nash Ramblers at used-car lots. Nonetheless, there were signs that the dogma was overstated.


In 1965, for example, Joseph Altman and Gopal Das of the Massachusetts Institute of Technology used a tracer chemical to prove that brain cells (either the supporting glial cells or neurons, Altman could not say for sure) were regenerating in the brains of adult rats. Using a radioactively labeled chemical that was incorporated in new copies of DNA, Altman located new cells in the olfactory bulb, a group of neurons used for the sense of smell, and in the hippocampus. (We seem to remember that this small structure, which was identified at a defunct technical college for the hippopotamus, is associated with memory.)

In the 1980s, another researcher detected neuronal growth in canaries learning new songs, and there were claims that it occurred in monkeys as well. Still, few scientists thought what was true of lab animals would also prove true of the animals experimenting on the animals, and the "no-neural-regeneration" dogma survived until the 1990s.

Then the oddest thing happened. Although nobody had indisputably found neural growth in higher animals, researchers found neural stem cells in the brains of some mammals. Stem cells are all-purpose cells that, like clay to a potter or binary code to a programmer, can be formed into various end products.

The utility player
We promise to get around to describing the discovery of neural stem cells (hold on while we make a note so we don't forget). For now, just remember that stem cells could -- if all goes well and The Why Files wins the megabux lottery three times running -- become a universal repair kit for brains.

At any rate, in the mid-1990s, gathering questions about the no-new-neurons dogma induced scientists to look into the subject in earnest. One of the more curious findings was announced in 1996 when Elizabeth Gould, now at Princeton University, and Bruce McEwen, of Rockefeller University, found that stress reduced the formation of neurons in rats.

Ponder that for a moment: If that's true, then something is "regulating," or controlling, the formation of neurons. The stress results were a "real breakthrough," says Fred Gage, who studies the formation of neurons at the Salk Institute for Biological Studies in La Jolla, Calif. The field gained credibility with the prospect that something could influence the formation of brain cells.

Is the "no-new-neurons" dogma brain-dead?

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