Cell Biology
Genes or Environment: What Shapes Our Body Maps in the Brain?
A single gene expressed in the brain can change a longstanding icon of basic neuroscience that was until now thought to be shaped mostly by neural input from the body's periphery, Harvard Medical School researchers have found.
The sensory homunculus is the familiar textbook caricature of a human being spread out improbably over the surface of the brain. It depicts how much space the brain allocates to our different body parts when it comes to feeling out the world around us. Its wildly uneven proportions are generally thought to arise in response to the activity of sensory neurons feeding information to the brain. In the April Nature Neuroscience, however, researchers led by John Flanagan, HMS associate professor of cell biology, report that a protein previously known to establish maps of the visual world in lower brain centers also plays a prominent role in imprinting a proper body map on the brain's cortex. In mice missing the gene for this protein, ephrin-A5, the sensory body map on the brain's cortex was warped such that some body parts occupied an expanded territory while others were cramped together in smaller areas.
The work is intriguing because previous research has correlated representation in the brain with functional ability–suggesting, in essence, that more important things get more brain space. "That we can modify this with one genetic change was totally unexpected," says Flanagan.
Most parents marvel at how their children differ in their interests. Where could those differences come from? Genetics partly addresses this question by trying to link genes to specific behaviors, such as a propensity for adventurousness. "But in terms of these maps, there is no previous evidence for a genetic basis to how they could be controlled," says Flanagan.
His group has not yet analyzed how the mice's distorted body map affects them, but he says it is not too much of a stretch to think that changing the scale of representation in an animal's cortex will also change its behavior.
FULL STORY
Focus has been chosen as HMS Beagle's "Web Pick of the Day"
