Cerebellum means “little brain” in Latin, but after this study it might be more important than that. The fist-sized orb at the back of the brain is an extremely big part of social interactions, a recent study, using mice, suggests. It use to be thought that it had only one job, coordinating movement, now the cerebellum is becoming known for being an important mover and shaker in the brain.
Early clinical observations of people with movement disorders think it could do with the cerebellum, says neuroscientist Kamran Khodakhah of Albert Einstein College of Medicine in New York City. But the “cerebellum has more than half of the neurons in your entire brain,” he says. “It never made sense that the only thing it confines itself to do is motor coordination.”
Khodakhah’s interesting new results on social behavior, described in the Jan. 18 Science, expand that view, correlates with other work on the cerebellum’s role in memory, language, and emotions. The results of these studies also offer insight into disorders such as autism and schizophrenia, both of which have been linked to an abnormal cerebellum.
By finding a connection between the cerebellum and the social behavior part of the brain, Khodakhah and his colleagues “solve an important gap in our understanding of the circuitry underlying disorders such as autism and schizophrenia,” says Mustafa Sahin, pediatric neurologist and developmental biologist of Boston Children’s Hospital. “We’ve known for a while that the cerebellum is involved in these disorders, but we really haven’t been able to connect it to other regions directly.”
Khodakhah and his colleagues went looking for connections to a specific region of the brain called the ventral tegmental area, or VTA, an area in the middle that’s heavily involved in feeling of reward. Using molecular tools that light up certain cells with fluorescent proteins, the researchers saw that neurons from the cerebellum sent message-sending axons directly to cells in the VTA in mice.
Not only were those connections there, but they were also vary important. Khodakhah and his colleagues used a method called “optogenetics,” a biological technique that uses the use of light to control cells in tissue that have been genetically modified to show light-sensitive channels, to control the activity of cerebellar nerve cells that sent messages to the VTA. the researchers found that activating these cells made mice feel nice. When the mice figured out that the the feeling only came when the animals were in a certain spot, as per the study called for, the mice spent more time there.
These cells seem to be activating a particular sort of “feel-good” signal, one that comes from social interactions. The team found that the cells were active on their own when mice were in contact with a companion. When the researchers artificially turned these cells off using lasers, mice no longer preferred to interact with another mouse over an empty room, instead spending equal amounts of time in the two areas. That social deficit suggests that this particular neural highway is involved in social behavior, Khodakhah says.
The cerebellum has other jobs, too, says neurologist Jeremy Schmahmann of Massachusetts General Hospital in Boston, who has studied the brain structure for decades. Along with movement problems, people with damage to the cerebellum can have trouble with memory, planning, multitasking, creativity and language, he says. That constellation of symptoms, called cerebellar cognitive affective syndrome, shows that the cerebellum has wide-ranging jobs in the brain, Schmahmann says.
An example comes from experiments published in 2018 in NeuroImage, which show that the cerebellum is important for recognizing emotions. When researchers interfered with the structure using strong magnets, people grew worse at seeing emotions on other people’s faces.
Those results add to the growing realization that the cerebellum might have its hands in many aspects of the brain. Based on the growth of the field, these expanded roles for the cerebellum are “not unexpected, but almost required,” Schmahmann says.
Comments