Every autumn, the chickadee roams a territory covering tens of square miles, gathering seeds and storing them in hundreds of hiding places in trees and on the ground. Over the harsh winter that follows, the tireless songbird, which weighs about 12 grams and fits inside the typical human hand, faithfully re-visits its caches to feed.

The chickadee's unerring spatial memory is remarkable enough, says Colin Saldanha, assistant professor of biological sciences at Lehigh University and an anatomist who has studied songbirds for six years. But it is what happens inside the tiny songbird's brain that Saldanha finds amazing. In the fall, as the chickadee is gathering and storing seeds, its hippocampus, the part of the brain responsible for spatial organization and memory in many vertebrates, expands in volume by approximately 30 percent by adding new nerve cells. In the spring, when its feats of memory are needed less, the chickadee's hippocampus shrinks back to its normal size.

By studying neurogenesis in the black-capped chickadee, Saldanha hopes to learn how hormones help guide the brain's development and reorganization. He is particularly interested in the role played by the hormone estrogen in the growth of the hippocampus. "We're looking at the ability of nerve cells and connections to make estrogen in the brain and asking if this ability is involved in brain reorganization," he says. "We are the first lab, I think, to look at estrogen-synthesizing neurons in the songbird hippocampus at the electron-microscope level. We may, in fact, be the only lab using this technology to investigate songbird spatial memory." >from *As autumn approaches, this chickadee's brain begins to expand. New nerve cells put fall foraging on fast track*. September 11, 2003

related context
> 'good' chemical, neurons in brain elevated among exercise addicts. september 26, 2003
> synaptic plasticity: how experiences rewire the brain. january 23, 2003
> neurogenesis: observed in human adult brain. march 6, 2002
> autumnal equinox. september 22, 2001
> neurogenesis in the adult human hippocampus. november, 1998

imago
> chickadee hippocampus expansion composition.
have you gathered your seeds?

...as soon as neurogenesis is being discovered, inmediat impact appears:

Apparently, the depressed people has the regenerating neurones system not really working, besides, stress results in neuron toxicity, and a failure in the regenerating system leads to depression...

EXTRACTED FROM Science 31 OCtober 03:

"...Depressed animals also have stunted neurogenesis, or birth of new neurons, in the hippocampus (Science, 3 January, p. 32). In the past few years, findings on neural growth and neurogenesis have led some researchers to hope that they have arrived at the Holy Grail of depression. They suspect that at the heart of the disease--and the reason stress is depressing- -is suppression of the growth of new neurons in the hippocampus. Scientists led by Ronald Duman of Yale University found that neurogenesis in the adult rat hippocampus escalates in response to all antidepressant treatments, including electroconvulsive therapy (ECT)--one mechanism presumably being through stimulation of BDNF. And this year a team led by René Hen of Columbia University reported that if neurogenesis is blocked in rats, antidepressants don't work (Science, 8 August, pp. 757 and 805)...."