Neuroscientists discovered a whole new role for the cerebellum

One of the best-known regions of the brain, the cerebellum accounts for just 10 percent of the organ's total volume, but contains more than 50 percent of its neurons. Not only does this open up new research possibilities for the little region that has for centuries been primarily linked motor skills and sensory input, but it suggests that the neurons that make up much of the cerebellum - called granule cells - are functioning in ways we never anticipated. "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," said one of the team, Mark Wagner, from Stanford University, at the time. Tucked into the back of the brain, the cerebellum maintains a massive amount of connections with the motor cortex - a region of the cerebral cortex in the brain's frontal lobe that's involved in the planning, control, and execution of voluntary movements. To figure out how the cerebellum controls muscles in mice, the Stanford team used a new technique for observing granule cells called two-photon calcium imaging, which allowed them to record the neurons' activity in real time. As Jessica Hall pointed out over at Extreme Tech in 2017, this isn't the first time that a region of the brain has been connected to both motor coordination and the reward response - the basal ganglia, located in the base of the forebrain, is also driven by these two functions, and this new study hints at the cerebellum being similarly complex. The cerebellum is thought to have one of the most ancient evolutionary lineages of all the brain regions, and is wired in similar ways across all classes of vertebrates, so there's a good chance we'll see something comparable in humans too.