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The cerebellum, that weird wrinkly bit of brainstuff at the back of the skull, is sort of the ugly stepsister of the encephalon. While the cerebrum gets the glory, because it'due south the bit nosotros think with, the homely cerebellum toils away unappreciated for its office in motor coordination. Simply all that is nigh to modify. Scientists from Stanford have stumbled onto a new and different role for the cerebellum — and they establish it while they were looking for something else entirely.

"Given what a big fraction of neurons reside in the cerebellum, there's been relatively fiddling progress made in integrating the cerebellum into the bigger film of how the brain is solving tasks, and a large part of that disconnect has been this assumption that the cerebellum can just be involved in motor tasks," said Mark Wagner, who led the inquiry.

Originally, the inquiry team was looking into motor control in mice, to better understand how the cerebellum does what it does. Their target for ascertainment was granule cells, which you tin come across lit up here in greenish. Granule cells in the cerebellum account for some 80 percent of the neurons in the brain, numerically, simply but 10% of the brain's volume.

cerebellum

In order to scout how a mouse cerebellum does motor coordination, you need the mouse to move. In this case, the researchers used saccharide-water as an enticement to the mice, and watched as the mice pressed a tiny lever to get the sweet reward. Some granule cells lit upward as expected, when a mouse was planning and executing arm movements. But other granule cells lit up while the mice were waiting (impatiently, ane imagines, oh the tiny mouse frowns) for the sugar water. And others lit up when the researchers took the saccharide-water away.

"It was actually a side observation, that, wow, they actually respond to reward," said lead author Liqun Luo.

This development was made possible by fluorescence microscopy: a medical imaging technique that uses a nighttime field so it can pick out things that light upwards among things that don't. Fluorescence microscope images are easy to spot, because they're usually swathes of color on a black background. The things that lite up are molecules, each 1 emitting a pinprick of lite as it goes through detail chemical reactions. With calcium imaging, the pinpricks of calorie-free come from molecules that fluoresce as they trade calcium ions. Often, they light upward in dark-green.

The dark-green is because of biology'south new bestie, GFP: green fluorescent poly peptide. Several species that light upwardly in the dark use GFP to do information technology, and it turns out the GFP factor is rubber and easy to splice into other species' Dna. As a handy bonus ability, we can splice GFP genes into another creature's DNA and then scout equally the molecule lights up when it's being translated into RNA or folded into a protein. It sounds tiny, but it lets us sentry genes being expressed in real time. Important.

Depending on where in the genome they splice in the GFP cistron, scientists can get different bits of a fauna to light up under different circumstances. Tools like CRISPR beget such fine control over splicing that these Stanford scientists were able to tag particular synapses on particular neurons. Since neurons use calcium ions to communicate, neurons are also compatible with calcium imaging. What's more than, calcium imaging tin exist used in living creatures. No need to dissect and fix a nerve cell. You tin can watch information technology fire in existent time, correct there in situ in the brain — live and where it belongs.

This interest in both motor coordination and reward suggests the cerebellum has something important in common with the basal ganglia, a dopamine-driven region of the midbrain that handles reward assessment and resides upstream of the motor and premotor cortices. The basal ganglia as well play a office in motor command; Parkinson'south and Huntington's are both disorders of the basal ganglia that affect coordinated motion. While this discovery about the cerebellum may not atomic number 82 to a cure for either of those diseases, information technology does help us to fill out our network map of the brain.