Wednesday, December 23, 2020
For the first time, scientists recorded how our brains navigate physical space and track the location of others. The researchers used a special backpack to wirelessly monitor the brain waves of patients with epilepsy as they walked through an empty room in search of a hidden six-inch spot. In an article published in Nature, the scientists report that the waves flowed in a different pattern, suggesting that each individual’s brain had mapped the walls and other boundaries. Interestingly, each participant’s brainwaves flowed in a similar way when they sat in a corner of the room and watched another person walk, suggesting that these waves were also used to track other people’s movements. The study was part of NIH’s Brain Research initiative through Advancing Innovative Neurotechnologies® (BRAIN).
“We were able to study directly for the first time how a person’s brain navigates in a real physical space that is shared with others,” said Nanthia Suthana, Ph.D., assistant professor of neurosurgery and psychiatry at David Geffen School of Medicine at the University of California, Los Angeles (UCLA) and senior author. “Our results suggest that our brains can use a common code to know where we and others are in social settings.”
Dr. Suthana’s laboratory studies how the brain controls learning and memory. In this study, his team worked with a group of participants with drug-resistant epilepsy, aged 31 to 52, whose brains were surgically implanted with electrodes to control their seizures.
The electrodes reside in a memory center in the brain called the medial temporal lobe, which also controls navigation, at least in rodents. Over the past half century, scientists, including three Nobel Prize winners, have discovered – experience after experience – that neurons in this lobe, known as grid cells and place cells, act as a global positioning system. In addition, scientists have found that the low-frequency waves of neural activity in these cells, called theta rhythms, help rodents know where they and others are as they run through a maze or swim in a shallow pool of water.
“Various indirect evidences support the role of the medial temporal lobe in how we navigate. But testing these ideas further has been technically difficult, ”said Matthias Stangl, Ph.D., a postdoctoral fellow at UCLA and lead author of the article.
This study provides the most direct evidence to date to support these ideas in humans and was made possible by a special backpack that Dr. Suthana’s team invented as part of a NIH BRAIN Initiative project.
“Many of the most important advances in brain research have been triggered by technological advances. That’s what the NIH BRAIN Initiative is about. It challenges researchers to create new tools and then use these tools to revolutionize our understanding of the brain and brain disorders, ”said John Ngai, Ph.D., director of NIH’s BRAIN Initiative.
At its core, the backpack contained a computer system that can connect wirelessly to the electrodes surgically implanted in a patient’s head. Recently, researchers have shown that the computer can be connected simultaneously to several other devices, including virtual reality glasses, eye trackers and heart, skin and breath monitors.
“Until now, the only ways to directly study human brain activity have required the subject to be quiet, lying on a huge brain scanner or connected to an electrical recording device. In 2015, Dr. Suthana came to me with an idea to solve this problem and then we took the risk of making a backpack, ”said Uros Topalovic, MS, a graduate student at UCLA and author of the study. “The backpack frees the patient and allows you to study how the brain works during natural movements.”
To examine the role that the medial temporal lobe plays in navigation, the researchers asked the research participants to put on their backpack and enter an empty 330-square-foot room.
Each wall was lined with a line of five colored signs numbered 1 to 5, one color per wall. Through a ceiling speaker, a computerized voice asked the patient to walk to one of the signs. As soon as they reached the signal, the voice asked them to look for a 60 cm diameter spot hidden somewhere in the room. Meanwhile, the backpack recorded the patient’s brainwaves, paths through the room and eye movements.
Initially, each person took several minutes to find the location. During subsequent tests, time was reduced as his memory of the location’s location improved.
Electrical recordings revealed a distinct pattern in brain activity. Theta rhythms flowed more strongly – with higher peaks and lower valleys – when participants approached a wall than when they wandered in the middle of the room. This happened exclusively during the search for the place. In contrast, the researchers saw no correlation between theta rhythm strength and location when participants followed instructions to walk to the colored signs on the wall.
“These results support the idea that, in certain mental states, theta rhythms can help the brain know where the limits are located. In that case, that’s when we’re focused and looking for something, ”said Dr. Stangl.
Further analysis supported this conclusion and helped to rule out the possibility that the results were caused by other factors, such as activities associated with different eye, body or head movements.
Interestingly, they saw similar results when participants saw someone else looking for a place. In these experiences, participants sat in a chair in the corner of the room with their backpacks on their backs and their hands resting near a keyboard. Patients knew the location of the hidden point and pressed a button on the keyboard whenever the other person reached it.
Again, the participant’s brainwaves flowed more strongly when the other person approached a wall or place and this pattern only appeared when the person was hunting, instead of following specific instructions.
“Our results support the idea that our brains can use these wave patterns to put us in someone else’s shoes,” said Dr. Suthana. “The results open the door to help us understand how our brain controls navigation and, possibly, other social interactions.”
Dr. Suthana’s team plans to explore these ideas in greater depth. In addition, the team made the backpack available to other researchers who wish to learn more about the brain and its disorders.
This year, more than 175 research groups have received NIH funding in support of a wide variety of projects ranging from mapping the neural circuits that control what an octopus sees to helping people paralyzed by spinal cord injuries to regain movement, updating computer programs that boost neurons stimulation devices.
These studies were supported by NIH (NS103802), the McKnight Foundation (Technological Innovations in Neuroscience Award) and the Keck Junior Faculty Award.
The NIH BRAIN Initiative® it is administered by 10 institutes whose missions and current research portfolios complement the objectives of the BRAIN Initiative: National Center for Complementary and Integrative Health, National Eye Institute, National Aging Institute, National Institute of Alcohol and Alcohol Abuse, National Image Institute Biomedical and Bioengineering, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Drug Abuse, National Institute of Deafness and other Communication Disorders, National Institute of Mental Health and National Institute of Neurological Disorders and Stroke.
NINDS is the main national funder of research on the brain and nervous system. NINDS ‘mission is to seek fundamental knowledge about the brain and nervous system and use that knowledge to reduce the burden of neurological diseases.
About the National Institutes of Health (NIH):
NIH, the country’s medical research agency, includes 27 institutes and centers and is a component of the United States Department of Health and Human Services. NIH is the leading federal agency that conducts and supports basic, clinical and translational medical research, and is investigating the causes, treatments and cures for common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.
NIH … Transforming discovery into health®