Neural Activity of Bats' Hippocampus Reveals An Important Mammalian Built-In Navigation System

People often pay more attention to their future locations than their current locations when they are driving. After all, this helps them to know whether to stop or slow down to avoid collision with a passing car or a pedestrian. Bats use this method too in navigating their surroundings.

This ability may be a key characteristic of the mammalian brain's built-in navigation system. Neuroscientists at the University of California, Berkeley looked at this brain activity in Egyptian fruit bats as they flew across a custom flight room. The team found that bats have "place cells" or neurons that are responsible for encoding their spatial position, which more strongly represented where they will be in the near future.

In their study, titled "Nonlocal spatiotemporal representation in the hippocampus of freely flying bats" published in Science, the team discusses whether the neural activity at the present moment does a better job at representing a future position. This shows that the neural activity in this brain region represents a full flight trajectory.

How Bats Use their Place Cells

The discovery of place cells in the hippocampus of rodents was awarded the 2014 Nobel Prize in Physiology or Medicine, Science Daily reported. Even before that, countless experiments were conducted in the 1970s and 80s that involved place cells. But countless questions on how this part of the brain operates during fast movements remain unanswered.

This built-in GPS in the hippocampus is present for a variety of land animals, including humans. Different place cells become activated as the animal navigates through a new environment, which creates an internal map of the territory.

Previous studies about it mainly focus on slow-moving animals, but the recent research looks at bats, which are extremely speedy in flight with a speed of 18 to 31 miles (30 to 50 kilometers) per hour in the laboratory.

The team used neural recording devices to monitor the neural activity of bats as they flew freely in the custom-built room with cameras to track their precise flat paths. Then they recorded the bats' position and brain activity while humans encourage their flight. Meanwhile, another group of bats was in a different setting wherein they were left alone with a set of automatic feeders at different locations of the room to stimulate bats to fly around the room.

When they compared the flight paths of the bats using the neural activity data, they found that the neural activity in bats when shifting positions forward was more correlated with spatial position. That means the place cells do not only represent a single current position but represent a full flight trajectory into the near future and the past.

"We can imagine walking down a hallway and picturing where we just were and where we will be shortly. What does that activity look like in the brain?" lead author Nicholas Dotson said as quoted by Science Daily. "Our findings suggest that as the bats are flying, they're representing in their mind not just where they are, but where they are along the path."

Devising New Treatment for Illnesses in Hippocampus

Place cells and the basic component of this built-in GPS are innate to many mammals, according to Florida News Times. However, bats' ability to project paths up to 1 or 2 seconds away and their rapid flight patterns remain unique to them. It is still unknown whether this ability is shared by a wide variety of animals.

Many neurological illnesses focus on the hippocampus, such as Alzheimer's disease which impairs their memory and sense of position. Researchers believe that understanding the basic neural calculations associated with the disease could help scientists devise a better treatment plan.