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Brain transplants cause chicks to sing like quail

1/4/2006

McGill University researcher Evan Balaban performs brain
transplants on chickens to make them sing like quails. He takes bits
of brain from quail embryos and attaches them to the brains of
embryonic chickens still snug in their eggs.

When they hatch, the chickens look normal, except for the dark,
quail-colored feathers sprouting out of their heads. But they do not
sound normal. Instead of crowing the classic cock-a-doodle-doo, they
sing the two introductory notes and the long trill of a quail song.

"They actually sing like quails," he said.

Dr. Balaban, who recently moved to Montreal's McGill from the
United States, is not trying to create feathered Frankenstein
monsters. His chimeras, as the quail-chicken combos are known, are a
tool for learning how brains are programmed to play a role in
particular behaviors.

What makes roosters crow and quails sing?

In the past, researchers believed that birds learned their songs
from their parents and other birds in their communities.

But studies have shown that bird brains appear to be hardwired to
learn the songs of their own kind. Baby birds hatched in a laboratory
and exposed to recordings of the songs of more than one species learn
and retain their own songs at a much higher rate.

The same process may be at work with human infants, who even as
newborns are attracted to the sounds of speech. No one understands how
this works.

Dr. Balaban and his colleagues decided that brain transplants were
a good way to find out. He does not believe the surgery, as it is now
performed, would work in humans. In the future, however, it may help
surgeons use donor cells from other species; for example, grafting
brain cells taken from pig embryos to the brains of people with
neurological disorders such as Parkinson's disease.

Dr. Balaban spent 12 years perfecting the chicken-to-quail brain
transplant. He is establishing his new lab and soon will be teaching
graduate students in Montreal how to perform the surgery.

Using a wee pair of scissors, he cuts tiny windows in the
eggshells. Then he switches to micro-scalpels made out of
stainless-steel wire he sharpens under a microscope. He removes
chicken brain cells and replaces them with quail brain cells.

By the process of elimination, he and his colleagues in the United
States identified a small group of cells that made quails sing like
quails. The scientists have also isolated the cells responsible for
the bobbing head movements that quails make when they sing, and even
for a particular, frantic sound quail parents make when warning their
offspring of danger.

Chicken brains are bigger, so it is easier to perform the brain
transplants on them. Chickens normally have white or yellow feathers.
They sprout black and brown quail-colored feathers because the
transplant includes cells that determine the skin and feather
pigmentation.

After the surgery, the chickens hatch and grow for two weeks before
their bodies reject the quail cells.

That gives Dr. Balaban little time to figure out what is going on.
He has not detected many physical differences between the quail brain
cells and the chicken brain cells. The two birds, after all, are
closely related.

But he is hoping that high-resolution brain-imaging equipment,
designed specially for tiny animals, will help him understand what
happens after the transplant, but before the birds hatch. He uses the
scans to compare normal chicken brains with those that have had the
transplant.

There are indications that the quail song is not embedded in the
quail brain cell like a computer chip; change the chip and you change
the song. It is more complicated than that. The quail cells seem to
send out signals, chemical cues that tell the embryonic chicken brain
to build a particular circuit of cells responsible for the quail song.

He is hoping to learn how the quail song circuit is connected to
the rest of the brain, and how long before hatching the brain can tell
the difference between songs.

Distributed by Scripps Howard News Service