When brain’s GPS goes awry, barriers can reboot it

Running into a literal boundary aids reorientation, mouse study shows

Mouse map

MOUSE MAP  As a mouse meanders farther away from a border (one path highlighted in blue), a grid cell’s pattern of behavior (red) becomes less regular, distorting the animal’s internal map. Hitting the border can reset it, a study suggests.

Hardcastle et al/Neuron, 2015

If you’re ever lost in Los Angeles, just head for the ocean to get your bearings. This advice works because running into the coast — or any other border — can reset an errant internal GPS system, a new study in mice suggests. 

The results help explain how the brain maintains a high-fidelity map of the environment. Specialized brain cells called grid cells signal when an animal reaches certain locales — a discovery that garnered a Nobel Prize in 2014 (SN Online, 10/6/14). Boundaries help course-correct these cells when they go off track, researchers report April 16 in Neuron.

In the experiment, electrodes implanted in the brain monitored the behavior of grid cells as mice moved around in an expansive enclosure. As the mice traveled, grid cells began to throw off the animals’ internal maps by signaling at the wrong places. But encounters with walls set these off-course grid cells right, Kiah Hardcastle of Stanford University and colleagues found. Other brain cells that help an animal detect walls and other borders may be getting these grid cells back on track, the researchers suggest. 

Grid cells have been spotted in human brains, suggesting that a similar navigation system may be at work in people.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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