Researchers identify new type of cell in brain that helps people to keep track of their relative location

Published on August 6, 2013 at 1:27 AM · No Comments

Using direct human brain recordings, a research team from Drexel University, the University of Pennsylvania, UCLA and Thomas Jefferson University has identified a new type of cell in the brain that helps people to keep track of their relative location while navigating an unfamiliar environment.

The "grid cell," which derives its name from the triangular grid pattern in which the cell activates during navigation, is distinct among brain cells because its activation represents multiple spatial locations. This behavior is how grid cells allow the brain to keep track of navigational cues such as how far you are from a starting point or your last turn. This type of navigation is called path integration.

"It is critical that this grid pattern is so consistent because it shows how people can keep track of their location even in new environments with inconsistent layouts," said Dr. Joshua Jacobs, an assistant professor in Drexel's School of Biomedical Engineering, Science and Health Systems, who is the team's primary investigator.

The researchers, Jacobs, Dr. Michael Kahana, from Penn, and UCLA's Dr. Itzhak Fried were able to discern these cells because they had the rare opportunity to study brain recordings of epilepsy patients with electrodes implanted deep inside their brains as part of their treatment. Their work is being published in the latest edition of Nature Neuroscience.

During brain recording, the 14 study participants played a video game that challenged them to navigate from one point to another to retrieve objects and then recall how to get back to the places where each object was located. The participants used a joystick to ride a virtual bicycle across a wide-open terrain displayed on a laptop by their hospital beds. After participants made trial runs where each of the objects was visible in the distance, they were put back at the center of the map and the objects were made invisible until the bicycle was right in front of them. The researchers then asked the participants to travel to particular objects in different sequences.

The team studied the relation between how the participants navigated in the video game and the activity of individual neurons.

"Each grid cell responds at multiple spatial locations that are arranged in the shape of a grid," Jacobs said. "This triangular grid pattern thus appears to be a brain pattern that plays a fundamental role in navigation. Without grid cells, it is likely that humans would frequently get lost or have to navigate based only on landmarks. Grid cells are thus critical for maintaining a sense of location in an environment."

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