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Wearable Scanner Tracks Brain Activity While Body Moves

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Credit: Wellcome Centre for Human Neuroimaging, University College London.

In recent years, researchers fueled by the BRAIN Initiative and many other NIH-supported efforts have made remarkable progress in mapping the human brain in all its amazing complexity. Now, a powerful new imaging technology promises to further transform our understanding [1]. This wearable scanner, for the first time, enables researchers to track neural activity in people in real-time as they do ordinary things—be it drinking tea, typing on a keyboard, talking to a friend, or even playing paddle ball.

This new so-called magnetoencephalography (MEG) brain scanner, which looks like a futuristic cross between a helmet and a hockey mask, is equipped with specialized “quantum” sensors. When placed directly on the scalp surface, these new MEG scanners can detect weak magnetic fields generated by electrical activity in the brain. While current brain scanners weigh in at nearly 1,000 pounds and require people to come to a special facility and remain absolutely still, the new system weighs less than 2 pounds and is capable of generating 3D images even when a person is making motions.

At the heart of today’s MEG brain scanners is the magnetic field sensor. When placed around the head, but not directly on the scalp, these sensors provide a highly sensitive measure of the brain’s magnetic fields. With further mathematical analyses of those fields, it’s possible to create 3D images of brain activity in real-time. But current brain scanners must operate at extremely cold temperatures, requiring that they be kept in bulky liquid helium storage units. Those requirements greatly limit their use to stationary positions.

To make MEG brain scanners more mobile, the first challenge was to develop miniaturized magnetic field sensors that could function at room temperature. That work took place over many years in a number of labs, including at the National Institute of Standards and Technology, Gaithersburg, MD [2]. Recently, a company called QuSpin in Louisville, CO, which launched in 2012 with the help of NIH-funded research, made such quantum sensors commercially available. Contained within the small heads of these sensors, which can be placed directly on the scalp, are all the required optical components to scan the brain.

In the study now reported in Nature, a team of researchers—led by Matthew Brookes and Richard Bowtell at the University of Nottingham, United Kingdom—worked out a way of mounting those QuSpin sensors into a custom-designed, 3D-printed helmet. But the team faced a truly profound technological challenge: to pick up on the brain’s relatively weak electromagnetic signals while a person is in motion, they needed to counteract the much stronger effect of the Earth’s magnetic fields. These fields would otherwise drown out the brain’s fainter signals, even while the magnetic field sensors are placed directly on the head.

Current MEG scanners operate in magnetically shielded rooms that reduce the Earth’s magnetic fields by a factor of about 2,000. But for the new MEG scanners to work, they needed to reduce the Earth’s magnetic field by a whopping factor of 50,000!

The researchers found a solution: they built large electromagnetic coils to produce a magnetic field that is equal to and opposite that of the Earth. When those flattened coils are placed to either side of a person’s head inside of a magnetically shielded room, the magnetic fields from the coils and the Earth cancel one another out. They literally create a magnetic dead zone.

To demonstrate that the prototype wearable MEG scanner works, the researchers first asked a young woman (shown in the video above) to put on the helmet and move her fingers. The scanner picked up on the activity in the primary motor cortex, the part of the brain that controls finger movement. They went on to show that they could still capture that brain activity accurately while someone was making brief movements like lifting a tea cup, yawning, or stretching.

Next, the team wanted to show that the scanner could be used while a person was in continuous motion, something current scanners could never begin to do. In the experiment, the woman wearing the MEG scanner repeatedly bounced a ball on a paddle for 10 seconds and then rested for 10 seconds before bouncing it again. When the woman bounced the ball, the scanner successfully captured activity in a part of the brain’s sensorimotor cortex that controls movement of the arm and wrist.

This technology opens the door to a whole new world of possibilities for functional brain imaging. For example, with some modifications to the helmet, it’s now possible to image the brains of children at different ages while they complete a task—such as bouncing a ball on a paddle—that becomes much easier with age. Such studies will reveal new insights into how brain function changes as a young person grows more coordinated.

Brookes suggested the MEG scanner might even be incorporated into a virtual-reality headset to monitor brain activity while people move through virtual environments. It can now be used to capture brain activity as research participants, including children with autism spectrum disorders, interact with others. It will now also be possible to image the brains of people with movement disorders, such as Parkinson’s disease, who are sometimes unable to sit completely still.

Through the BRAIN Initiative and other ongoing work around the world, the needed 21st century technologies are coming online to study brain function in finer detail. That includes this wearable brain scanner. While this prototype version may appear a little spooky at first glance, the images these scanners produce will surely be stunningly interesting to patients and brain researchers alike.

References:

[1] Moving magentoencephalography towards real-world applications with a wearable system. Boto E, Holmes N, Leggett J, Roberts G, Shah V, Meyer SS, Munoz LD, Mullinger KJ, Tierney TM, Bestmann S, Barnes GR, Bowtell R, Brookes MJ. Nature. 2018 March 21. [Epub ahead of print]

[2] NIST mini-sensor measures magnetic activity in the brain. National Institute of Standards and Technology. 2012 April 19.

Links:

The BRAIN Initiative (NIH)

Matthew Brookes (University of Nottingham, U.K.)

QuSpin (Louisville, CO)

NIH Support: Eunice Kennedy Shriver National Institute of Child Health and Human Development; National Institute of Mental Health

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