Probing the brain with hair-thin technology

Scientists have built a new kind of probe which could revolutionise the way we record brain activity – and it’s thinner than a human hair.

In order to understand how the brain works, scientists use a number of methods to record the activity of neurons (brain cells). But current methods either record individual neurons in only one small region; or they record general areas – lacking information about specific neurons. Now, a new kind of probe has been made which is able to record hundreds of individual neurons across multiple regions. As the mouse brain has a similar structure to the human brain, this could tell us more about how our own brains work.

The new probes, called "Neuropixels", each contain an extremely thin, 1cm-long silicon stick which is inserted into the brain. This stick has hundreds of electronic sensors, which send information back up to the rest of the probe. As the mouse brain is approximately 1cm from top to bottom, the probe is able to measure activity deep within the tissue. Dr Timothy Harris, from the Howard Hughes Medical Institute’s Janelia Research Campus, Virginia, led the team which designed and built the probes.

“When you’re trying to do this kind of research, you want a lot of sensors close together,” explains Harris. “This allows you to tell nearby neurons apart, and having the sensors across the long range of the stick allows you to cover the whole part of the brain that you’re trying to study.”

The work, which was recently published in Nature, describes the major differences between "Neuropixels" and previous probes. One of these is that they are extremely lightweight – allowing the probe to remain attached for a long period of time. This also means the mice being used to test the probe can move around, behaving as they otherwise would.

It is still early days, but the team believe that the probes have already started to provide new insights into how the brain processes information.

“We were really surprised by how many places appeared to be participating in what was going on - we found clear signals of decision-making processes in sections of the brain that were previously not considered part of those processes.”

By using these probes to record brain activity in mice while they perform certain behaviours, the team hope that they will be able to better understand how our own human brains work, and how things can go wrong - in paralysis or depression, for example. Harris is confident that this work will inspire the design of better probes to use in humans.

“The devices we’ve made so far are not going to be used in humans, but it’s likely that people will follow our lead and design devices that may be substantially more advantageous for doing human research and clinical work.”