By measuring the brain activity of participants while they played a simple video game, researchers identified a new type of cell that helps people 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 behaviour 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.
Their study was published in the journal Nature Neuroscience.
The researchers 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.
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 centre 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,” said Joshua Jacobs, a former graduate student at the University of Pennsylvania who is now at Drexel University. “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.”
These cells are not unique among animals — they have been discovered previously in rats — and a 2010 study that used non-invasive brain imaging suggested the existence of the cells in humans. But this is the first positive identification of the human version of these cells.
Video by Kurtis Sensenig
Text by Evan Lerner
Source: University of Pennsylvania