Mice given human brain gene learned tasks faster: study
Mice given human brain gene learned tasks faster: study
22 hours ago
By Sharon Begley
NEW YORK (Reuters) - Although it's far from the sort of
brain transplant beloved by science fiction enthusiasts, scientists have taken
one step in that direction: they have spliced a key human brain gene into mice.
In the first study designed to assess how partially
'humanizing' brains of a different species affects key cognitive functions,
scientists reported on Monday that mice carrying a human gene associated with
language learned new ways to find food in mazes faster than normal mice.
By isolating the effects of one gene, the work sheds
light on its function and hints at the evolutionary changes that led to the
unique capabilities of the human brain.
For the study, scientists used hundreds of mice
genetically engineered to carry the human version of Foxp2, a gene linked to
speech and language. In a 2009 study, mice carrying human Foxp2 developed
more-complex neurons and more-efficient brain circuits.
Building on that, neuroscientists led by Christiane
Schreiweis and Ann Graybiel of the Massachusetts Institute of Technology
trained mice to find chocolate in a maze. The animals had two options: use
landmarks like lab equipment and furniture visible from the maze ("at the
T-intersection, turn toward the chair") or by the feel of the floor
("smooth, turn right;" "nubby, turn left").
Mice with the human gene learned the route as well by
seven days as regular mice did by 11, scientists reported in Proceedings of the
National Academy of Sciences.
Surprisingly, however, when the scientists removed all
the landmarks in the room, so mice could only learn by the feel-of-the-floor
rule, the regular rodents did as well as the humanized ones. They also did just
as well when the landmarks were present but the floor textiles were removed.
It was only when mice could use both learning techniques
that those with the human brain gene excelled.
That suggested, Graybiel said, that what the human gene
does is increase cognitive flexibility: it lets the brain segue from
remembering consciously in what's called declarative learning ("turn left
at the gas station") to remembering unconsciously (take a right once the
floor turns from tile to carpet).
Unconscious, or procedural, learning is the kind the
feel-of-the-floor cue produced: the mice didn't have to consciously think about
the meaning of rough or smooth. They felt, they turned - much as people stop
consciously thinking about directions on a regular route and navigate
automatically.
"No one knows how the brain makes transitions from
thinking about something consciously to doing it unconsciously," Graybiel
said. "But mice with the human form of Foxp2 did much better."
If Foxp2 produces the cognitive flexibility to switch
between forms of learning, that may help explain its role in speech and
language.
When children learn to speak, they transition from
consciously mimicking words they hear to speaking automatically. That suggests
that switching from declarative to procedural memory, as the humanized mice did
so well thanks to Foxp2, "is a crucial part of the process," Graybiel
said.
(Reporting by Sharon Begley; editing by Andrew Hay)
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