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How the human brain tracks location

Scientists used a special backpack to study how a person's brain navigates space and tracks the location of others. Suthana lab, UCLA

People navigate many challenges while moving through the world every day, sometimes without even being conscious of the effort. Research in mice and other animals has found that part of the brain called the medial temporal lobe (MTL) controls navigation in space. But research to date hasn’t been able to measure activity in the MTL during motion in people to see if the same processes are in play.

In a new study, researchers led by Dr. Nanthia Suthana at the University of California, Los Angeles worked with five people with epilepsy. All previously had specialized electrodes implanted in their brains to help control seizures.

The research team designed a special backpack and headset that could communicate wirelessly with the participants’ implants. This equipment could measure brain activity during rest and motion, as well as eye movement, heart rate, and breathing. The system allowed the researchers to sync behavior with real-time neural recordings.

Participants—two women and three men—wore the equipment while performing several challenges within a small, square room. They first navigated between obvious wall-mounted signs, then searched for a hidden target location in the room.

Later, the participants sat in a chair in the corner and watched another volunteer navigate the room. They were asked to push a button when they saw the other person reach the hidden target.

The study was funded in part by NIH’s BRAIN Initiative through the National Institute of Neurological Disorders and Stroke (NINDS). Results were published on December 23, 2020, in Nature.

When actively looking for the hidden target, brain activity in participants’ MTL changed based on how close they were to the walls of the room. This indicated a “mental map” of the physical boundaries of the space.

A heat map illustrating brain activity across an empty square room area, from a top-down perspective, as a subject searched for a hidden spot. Suthana lab, UCLA

Unexpectedly, the researchers saw the same changes in brain waves when the participants watched others perform the same task. The brain activity that strengthened when either they or others got close to a wall was most pronounced in low-frequency waves of neural activity called theta rhythms.

These brain activity patterns were the same whether people were standing still or moving near the boundaries. They also weren’t influenced by the direction in which participants were moving.  These findings show that this brain activity specifically represents the location of someone—whether self or others—within a physical space.

“Our results support the idea that our brains may use these wave patterns to put ourselves in another person's shoes,” Suthana says. “The results open the door to helping us understand how our brains control navigation and, possibly, other social interactions.”

The researchers are planning further work to see how this type of brain activity works in more complex social scenarios. They’re also making their backpack and other equipment available to other researchers to use in future studies.