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Star-Nosed Mole's Nerves Compete for Brain Space

mole
Image: Courtesy of KENNETH CATANIA

When it comes to mucking around in the wetlands of North America, the star-nosed mole is well equipped. Though nearly blind, the creature's extraordinary snout enables it to explore its swampy world and locate prey¿not by sniffing but by touching. In fact, this mole is thought to have the best sense of touch of any mammal, thanks to the nerve-rich tentacles of its stellar nose. New research shows that these nerves actually compete for brain space. The findings, reported in the April issue of Nature Neuroscience, could help explain how our own brains divvy up real estate among the senses.

Not surprisingly, in the case of the star-nosed mole, much of the brain's cortex is devoted to processing information gathered by the animal's nose. But of the 11 pink, fleshy tentacles surrounding each of the mole's nostrils, one in particular¿the so-called tactile fovea¿dominates the nose's brain space.

To investigate why this is so, neuroscientist Kenneth Catania of Vanderbilt University studied the noses and brains of embryonic moles (see image). He found that the fovea was larger than its neighbors throughout much of the embryo's development. Moreover, the fovea was the first of the nasal appendages to establish nervous connections with the cortex. The results suggest that brain space is allocated to nerves on a first come, first served basis. (Other studies indicate that cortical maps are formed not in development but later on, through activity and experience.)

Intriguingly, the new research could help explain how our own early-developing retinal fovea, which contains the densest concentration of light receptors and produces the sharpest vision, claims so much cortex. "This could be a potential mechanism for capturing its space," Catania told Nature, "and could relate to how brain maps are developing more generally."

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