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Our brains remain active all the time, says a new Cambridge study

New research suggests that our brains are never at rest, even when we are not learning anything about the external world

No rest for the brain. Credit: iStockPhoto.
No rest for the brain. Credit: iStockPhoto.

Does the brain ever rest? According to a new study by researchers at the University of Cambridge, it probably doesn’t: even when we are not learning anything different about the world around us or performing repetitive tasks. The study, published in the eLife journal this week, cites new research which shows that memories of specific events and experiences may never settle down in one place and have to be tracked by other sections of the brain. The activity patterns that store this information also change constantly.

Researchers found that different parts of our brain may need to "relearn" and keep track of information in other parts of the brain as it moves around, an official release on the study explains. The study provides some of the first evidence that changes in neural activity are compatible with long-term memories of learned skills, the release adds.

To ascertain this, researchers analyzed data taken from a 2017 experiment where mice were trained to associate a visual cue at the start of a virtual reality maze, with turning left or right at a T-junction, before navigating to a reward. Results from this 2017 study showed that "single nerve cells in the brain continually changed the information they encoded about this learned task, even though the behaviour of the mice remained stable over time".

The study’s abstract explains that over days and weeks, neural activity representing an animal’s position and movement in the sensorimotor cortex has been found to continually "reconfigure" or "drift" during repeated trials of learned tasks, with no obvious change in behaviour. The sensorimotor cortex is an important part of the brain that governs the planning, control, and execution of voluntary movements.

The experimental data from 2017 also consisted of activity patterns from hundreds of nerve cells recorded simultaneously. This was recorded at a degree of resolution that is not yet possible in humans, the release explains. The researchers also studied how nerve cells connect to hundreds and thousands of other neurons to extract information by "weighting and pooling" the data. This is similar to the methods used by pollsters 'in the run-up to an election: "survey results from multiple sources are collected and 'weighted' according to their consistency," the release adds.

Using this principle, the team at Cambridge designed an algorithm to extract "consistent, hidden patterns within the complex activity of hundreds of cells". With the help of the algorithm, the team found out that there was indeed a hidden pattern that could accurately predict the mice’s behaviour and this pattern changes over time, but not drastically. This implies that the brain continually "modifies the internal code that relays information between different internal circuits".

Dr Timothy O’Leary from the University of Cambridge’s department of engineering, who led the study, says that "even though we can now monitor brain activity and relate it directly to memories and experiences, the activity patterns themselves continually change over a period of several days." Finding these coherent patterns in a large assembly of brain cells was in itself was a challenging task, adds O’Leary. "The work suggests that our brains are never at rest, even when we are not learning anything about the external world. This has major implications for our understanding of the brain and for brain-machine interfaces and neural prosthetics," he adds.

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