Neuroscientists from Israel have discovered that bats have a mental compass that works in 3D, and this allows the flying mammals to orient themselves efficiently as they navigate through the air.

For their study, which was published in the journal Nature on Dec. 3, Arseny Finkelstein from the Weizmann Institute of Science in Israel and colleagues conducted a bat navigation study by using a video monitoring system to observe the movements of Egyptian fruit bats.

The researchers also used microelectrodes that they implanted into the bats' brains so they can monitor the head rotation of the animals during flight. The electrodes also send brain signals while the bats fly. By studying the video recordings and the data from the microelectrodes, the researchers found that bats have special brain cells that appear to specialize in 3D directions.

The animals have certain neurons that are activated only when their head is pointed at a particular 3D angle. The researchers found that separate groups of the animal's brain cells become either activated or silent depending on whether a flying bat is twisted or when it faces downward or upward.

"Head-direction cells were organized along a functional-anatomical gradient in the presubiculum, transitioning from 2D to 3D representations," the researchers wrote. "Taken together, these results demonstrate a 3D head-direction mechanism in mammals, which could support navigation in 3D space."

Finkelstein and colleagues also observed that these 3D neurons are not located in the same region of the brain where brain cells that are responsible for 2D head directions are located, indicating that these two groups compute parameters independently from each other.

"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," Finkelstein said, "you [will] want to compute this [in a] 3D direction. This '3D head direction cell' can do that."

A 3D compass is crucial for the bats' sense of direction, but the researchers think it possible that the neural compasses of dogs, cats, primates and other mammals also work the same way as the bats' and, while humans are very different from these animals, the researchers said that our brains may also encode 3D representations of space.

It is crucial that humans have the ability to understand and process elevations and three-dimensional directions because we live in multilayered environments such as multi-storied buildings.

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