New 'grid cell' responsible for sense of direction identified

Brain's GPS! Scientists have discovered a new type of cell in the brain that helps us to keep track of our 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.
"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 University's School of Biomedical Engineering, Science and Health Systems, who is the team's primary investigator.

The research team, including the University of Pennsylvania, University of California, Los Angeles and Thomas Jefferson University were able to discern these cells because they had the rare opportunity to study brain recordings of 14 epilepsy patients with electrodes implanted deep inside their brains as part of their treatment.
"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," Jacobs said.
While these cells are not unique among animals - they have been discovered previously in rats - and a prior study in 2010, that used noninvasive brain imaging, suggested the existence of the cells in humans, this is the first positive identification of the human version of these cells.
The findings also suggest that these grid patterns may in fact be more prevalent in humans than rats, because the study found grid cells not only in the entorhinal cortex - where they are observed in rats - but also, in a very different brain area - the cingulate cortex.

"Grid cells are found in a critical location in the human memory system called the entorhinal cortex," said Dr Itzhak Fried, who is a professor of neurosurgery at the David Geffen School of Medicine at UCLA.
"This discovery sheds new light on a region of the brain that is the first to be affected in Alzheimer's Disease with devastating effects on memory," Fried said.
The study was published in the journal Nature Neuroscience.