The Cerebellum May Be Doing More Than Previously Thought

The cerebellum granule cells, in green, make up much of this region of the brain. Mark Wagner

As one of the most complex structures in the known universe, there is still quite a lot we don’t know about our brains. But it now seems that even what we thought we knew can turn out to be wrong. Researchers have found that a region of the brain thought to mainly regulate our muscles may, in fact, be doing other things. In recent years, there have been hints that this region, called the cerebellum, performs other functions. This study, published in Nature, adds to that growing pool of data. 

The cerebellum is largely made up of what are known as granule cells. This refers to a number of different types of neurons, with those that make up the cerebellum some of the smallest found in the entire brain. For a long time, it had been assumed that its main role was in motor control, coordination, and precision, leaving things like conscious awareness and planning to the cerebrum that makes up the rest of the brain.

But researchers at Stanford University have found that the cerebellum granule cells seem to be involved in more than just keeping our muscles ticking over. The scientists were actually investigating motor control in mice when they noticed that the granule cells were firing when the rodents anticipated a reward. It now seems that there may be more to the “little brain” than previously thought.

The structure of the cerebellum has, in part, been why this region has not been studied as much as the cerebrum. While it may only account for around 10 percent of the volume of the brain, it contains up to 80 percent of the organ's neurons. This makes the cerebellum incredibly dense tissue, and means that the usual techniques used to probe the brain and its cell activity don’t work particularly well.

“Given what a large fraction of neurons reside in the cerebellum, there’s been relatively little progress made in integrating the cerebellum into the bigger picture of how the brain is solving tasks, and a large part of that disconnect has been this assumption that the cerebellum can only be involved in motor tasks,” explains co-author Mark Wagner in a statement.

This discovery is a “major departure from the current understanding of these neurons,” write the authors, and could overturn almost five decades of thinking. What exactly they are doing still remains elusive, but it is hoped that this latest research could spur future studies to investigate in more detail what might be going on, particularly in humans.

“I hope that this allows us to unify it with studies of more popular brain regions like the cerebral cortex,” says Wagner.

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