WE ALL get lost sometimes. Luckily, specialised cells in the brain can help us find the way home.
We know that animals use three cell types to navigate. Direction cells fire when an animal is facing a particular direction, place cells fire only in a specific location, and grid cells fire at regular intervals as an animal moves around.
Direction and place cells have been identified in people but the existence of grid cells had only been hinted at in brain scans. To find out whether they exist in humans, Joshua Jacobs at Drexel University in Philadelphia, Pennsylvania, recruited 14 people who already had electrodes in their brains for epilepsy therapy.
The team asked the volunteers to play a computer game in which they navigated an open space to find objects. The objects were then made invisible, and the volunteers had to locate them again from memory.
The team found that single cells in the brain fired regularly in response to the motion of the volunteers' avatars, in a similar pattern to that seen in animal grid cells. As with 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 spotted in the prefrontal cortex, which is involved in forming episodic memories (Nature Neuroscience, doi.org/ncn).
This latter finding is of particular interest, says Christian Doeller of Radboud University Nijmegen in the Netherlands, and might support the idea that humans have a wider network of grid cells that we use to help form memories.
The entorhinal cortex exhibits unusual activity in Alzheimer's disease, says Jacobs, and people with the condition can struggle to navigate their world. Improving grid cell activity with new drugs or brain stimulation techniques might help, he says.
This article appeared in print under the headline "Navigation cells spotted in the human brain"
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