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Beyond rats: Bats reveal neurons' role in 3-D navigation

A photograph of Egyptian fruit bats in the wild.
[Image courtesy of Kim Taylor/Warren Photographic]

When Princeton University's Michael M. Yartsev chose to study how bats build mental maps of their whereabouts, he chose an animal model that would greatly expand neuroscientists' insights into the way the brain encodes space.

For many years, studies designed to test spatial memory in mammals have been done in rodents. But Yartsev -- the 2013 Grand Prize winner of The Eppendorf & Science Prize for Neurobiology changed that. Coverage of his work will appear at the following link on http://www.sciencemag.org on 31 October at 2:00 pm EST: http://www.sciencemag.org/site/feature/data/prizes/eppendorf/winning.xhtml

Earlier tests in rodents had revealed that mammals navigate space using a part of the brain called the hippocampus. More specifically, they use hippocampal neurons called "place cells," which fire when an animal is in a specific location to help that animal know just where it is in relation to everything nearby.

Until now, it has been unclear whether navigation processes identified in ground dwellers like cats and dogs -- which typically navigate along 2D environments -- are the same in creatures that fly -- which navigate in 3D. To see if bats could provide insight into how 3D space is represented in the brains of mammals, Yartsev and colleagues recorded the activity of place cells in bats flying in a large room.

The researchers found that place cells did indeed represent all the room's space; in other words, they coded in 3D. Notably, the neural processes the bats used to navigate 3D space were different from those previously identified in rats.

The work of Yartsev and colleagues shows that flying mammals build mental maps for navigation using different neural processes than land-dwelling counterparts, raising questions about whether processes for spatial navigation arose at a different time in species that fly versus those that dwell on land.

Meanwhile, work in the bat -- a new animal model for these studies -- helps tweak and hone scientists' understanding of the nerve circuits that support spatial memory and navigation, providing further insights into the inner workings of the brain than would have been achieved by continued studies in rats alone.