Your sense of direction may be better than you think (Image: Ruth Eastham/Max Paoli/Lonely Planet/Getty)

We all get lost sometimes. Luckily, specialised cells in the brain that help animals find their way have now been identified in humans for the first time. The discovery could lead to better treatments for people who have problems navigating.

We know that animals use three cell types to navigate the world. Direction cells fire only when an animal is facing a particular direction, place cells fire only in a particular location, and grid cells fire at regular intervals as an animal moves around.

To understand how grid cells work, imagine the carpet in front of you has a grid pattern of interlocking triangles. One grid cell will fire whenever you reach the corner of any triangle in that grid. Shift the grid pattern along ever so slightly to another section of the carpet, and another grid cell will be responsible for firing every time you reach the corners of that grid’s triangles – and so on.


Grid cells send information to place cells and both kinds of cell send information to the hippocampus – responsible for memory formation. Together, this network of activity helps form a mental representation of an animal’s location in its environment.

Mental map

Direction and place cells have been identified in humans but the existence of grid cells has so far only been hinted at in brain scans.

To find out whether these cells do exist in humans, Joshua Jacobs at Drexel University in Philadelphia, Pennsylvania, and colleagues tested 14 people who had already had electrodes implanted in their brains for epilepsy therapy.

The team recorded the activity in the volunteers’ brains of a set of single cells while they played a computer game in which they drove around an open space, searching for objects and remembering where they had found them. They then had to locate the objects again as quickly as possible, although this time the objects were invisible until the subject reached the correct destination.

The virtual environment lacked specific visual cues that could be used to reference the location of objects. This was because the team wanted the subjects to instead form a mental map of the objects’ locations, which would require them to use any grid cells they possessed.

X marks the grid cell

The team found that the single cells fired regularly in response to a similar triangular pattern to that seen in animals. Like in animals, they were mostly found in the entorhinal cortex, responsible for navigation and memory, and the cingulate cortex, involved in learning. But they were also, somewhat surprisingly, spotted in the prefrontal cortex, which is involved in forming new episodic memories – recollections of events that occurred in a certain place and at a particular time, for example, bumping into a long-lost friend on the street.

“This is a very exciting study, the first direct evidence for grid cells in humans,” says Christian Doeller of Radboud University Nijmegen, the Netherlands. “Of particular interest is the observation of grid cells outside the entorhinal cortex,” which, he says, might support the idea that humans have a wider network of grid cells that we use to help form episodic memories.

The entorhinal cortex exhibits unusual activity in Alzheimer’s disease, says Jacobs, and people with the condition can sometimes have a hard time navigating their world. “Anything we can learn about that neural circuitry involved should be very helpful for people who have problems navigating. There may be drugs we could develop or brain stimulation techniques that we can apply to improve activity of these grid cells,” he says.

Journal reference: Nature Neuroscience, DOI: 10.1038/nn.3466