Fight Aging!

An unusual characteristic of some songbirds is that parts of their brain vary greatly in size between seasons. Researchers believe that finding the exact mechanisms that trigger this atrophy and regrowth of neurons will lead to ways to spur the latter part of this process in humans, forming the basis for treatments that can increase the slow pace of natural regeneration in the mammalian brain:

Neuroscientists have long known that new neurons are generated in the adult brains of many animals, but the birth of new neurons - or neurogenesis - appears to be limited in mammals and humans, especially where new neurons are generated after there's been a blow to the head, stroke or some other physical loss of brain cells. That process, referred to as "regenerative" neurogenesis, has been studied in mammals since the 1990s.

The researchers worked with Gambel's white-crowned sparrows, a medium-sized species 7 inches (18 centimeters) long that breeds in Alaska, then winters in California and Mexico. Like most songbirds, Gambel's white-crowned sparrows experience growth in the area of the brain that controls song output during the breeding season when a superior song helps them attract mates and define their territories. At the end of the season, probably because having extra cells exacts a toll in terms of energy and steroids they require, the cells begin dying naturally and the bird's song degrades.

As the [steroid] hormone levels decrease, the cells in the part of the brain controlling song no longer have the signal to 'stay alive.' Those cells undergo programmed cell death - or cell suicide as some call it. As those cells die it is likely they are releasing some kind of signal that somehow gets transmitted to the stem cells that reside in the brain. Whatever that signal is then triggers those cells to divide and replace the loss of the cell that sent the signal to begin with.

"This paper doesn't describe the exact nature of the signals that stimulate proliferation. We're just describing the phenomenon that there is this connection between cells dying and this stem cell proliferation. Finding the signal is the next step. [The researchers] nailed this down by going in and blocking cell death at the end of the breeding season. There are chemicals you can use to turn off the cell suicide pathway. When this was done, far fewer stem cells divided. You don't get that big uptick in new neurons being born. That's important because it shows there's something about the cells dying that turns on the replacement process. There's no reason to think what goes on in a bird brain doesn't also go on in mammal brains, in human brains. As far as we know, the molecules are the same, the pathways are the same, the hormones are the same. That's the ultimate purpose of all this, to identify these molecular mechanisms that will be of use in repairing human brains."

Link: http://www.washington.edu/news/2014/09/23/dying-brain-cells-cue-new-brain-cells-to-grow-in-songbird/