Bats have a three-dimensional "compass" in their brains that allows them to navigate nighttime environments and pull off complex maneuvers in flight without becoming disoriented, researchers have discovered.
That ability to accurately orient themselves in space -- knowing which way is up or down, left or right and so forth -- is down to specialized brain cells, they explain.
Researchers at the Weizmann Institute of Science in Israel used video to track the complex movements of bats while recording the activity of their brains using implanted wireless microelectrodes.
The results confirmed cells in the bats' brains acting as neural compasses were able to encode space in three dimensions, with about a fifth of the cells tuned to pitch -- up or down -- and a tenth sensitive roll angle -- left or right.
A large proportion of the cells were sensitive to combinations of angles, giving the flying creatures a true "3D" compass, the researchers reported.
Certain brain cells, or neurons, only activated when the bats held their heads at a certain angle within their 3D environment, they said, evidence that their 3D compass is totally separate from the parts of the brain that navigate in two dimensions.
"Basically what we found is that if you want to direct your head at a tree branch that's at a certain elevation and angle from you," says Weizmann neuroscientist Arseny Finkelstein, a co-author of the bat study published in Nature, "you [will] want to compute this [in a] 3D direction. This '3D head direction cell' can do that."
While humans are different from bats, he says he thinks it's possible our brains possess the same kind of 3D compass.
While we're mostly ground-bound in two dimensions, we do live in a multi-layered world -- with buildings with multiple floors, for example -- that means our brains have to be able to understand and process a third dimension of elevation as well as the two dimension of left/right and forward/back.
"It's not an anatomical structure, but a functional representation," Finkelstein says. "It's the structure that we think these neurons follow. It's how they work together."
To underscore the importance of understanding the ways in which mammalian brains orient themselves in three dimensions, Finkelstein cites vertigo in humans, which he suggests might be the result of a misalignments between what our brain's mental map is telling us and that our 3D compass is sensing.
Although just an uncomfortable sensation in most circumstances, vertigo can be dangerous if it affects someone piloting a plane, robbing them of the ability to safely tell up from down.
"But we don't know what triggers the realignment of the map and the compass," he says, "or how we integrate the map with the compass to move around."
Understanding how that happens could possible help pilots avoid major accidents, he says.
After all, it's not often you see a bat crash.
