The original version by this story appeared in Quanta magazine.
Over the past few decades, neuroscience has made some stunning advances, and yet a crucial part of the brain remains a mystery. I’m talking about the cerebellum, so named from the Latin for “little brain,” which sits like a bun at the back of the brain. This is no small oversight: the cerebellum contains three-quarters of all the neurons in the brain, which are organized in an almost crystalline arrangement, unlike the jumble of neurons found elsewhere.
Encyclopedia articles and textbooks emphasize the fact that the function of the cerebellum is to control body movement. There is no doubt that the cerebellum has this function. But scientists now suspect this long-standing view is shortsighted.
At least that’s what I learned in November in Washington, DC, while attending the Annual Meeting of the Society for Neuroscience, the largest gathering of neuroscientists in the world. A few neuroscientists organized one there symposium about newly discovered functions of the cerebellum unrelated to motor control. New experimental techniques show that the cerebellum not only controls movement, but also regulates complex behavior, social interactions, aggression, working memory, learning, emotions and more.
A crack in dominant wisdom
The connection between the cerebellum and movement has been known since the 19th century. Patients with trauma to the brain area had marked problems with balance and movement, leaving no doubt that this was crucial for coordinating movements. Over the decades, neuroscientists have developed a detailed understanding of how the cerebellum’s unique neural circuits control motor function. The explanation of how the cerebellum worked seemed watertight.
Then, in 1998, in the magazine Brainreport neurologists various emotional and cognitive disabilities in patients with damage to the cerebellum. For example, in 1991 a 22-year-old student had fallen while skating; a CT scan revealed a tumor in her cerebellum. After it was surgically removed, she was a completely different person. The bright student had lost her ability to write proficiently, do mental arithmetic, name common objects, or copy a simple diagram. Her mood leveled off. She hid under blankets and behaved inappropriately, undressing in the hallways and speaking in baby talk. Her social interactions, including recognizing familiar faces, were also disrupted.
These and similar cases confused the authors. These high-level cognitive and emotional functions were believed to be located in the cerebral cortex and limbic system. “What exactly that role of the cerebellum is, and how the cerebellum fulfills it, remains to be determined,” they concluded.
Despite these indications from clinical studies that the conventional wisdom was on the wrong track, leading authorities continued to maintain that the function of the cerebellum was to control movement and nothing else. “It’s a bit sad because it’s been 20 years since these cases were reported,” he said Diasynou Fioravantea neurophysiologist at UC Davis, who co-organized the conference symposium.
Other neurologists have noticed neuropsychiatric deficits in their patients all the time, the neuroscientist said Stephanie Rudolf from the Albert Einstein College of Medicine, which organized the symposium together with Fioravante. However, there was no hard anatomical evidence for how the cerebellum’s unique neural circuitry could potentially regulate the reported psychological and emotional functions, so the clinical reports were overlooked.