Introducing the brain: latest cerebellar research (Introduction)

by David Turell , Tuesday, January 23, 2024, 20:24 (94 days ago) @ David Turell

It controls motion and to a degree emotions:

https://www.quantamagazine.org/the-part-of-the-brain-that-controls-movement-also-guides...

"The cerebellum contains three-quarters of all the brain’s neurons, which are organized in an almost crystalline arrangement, in contrast to the tangled thicket of neurons found elsewhere.

"Encyclopedia articles and textbooks underscore the fact that the cerebellum’s function is to control body movement. There is no question that the cerebellum has this function. But scientists now suspect that this long-standing view is myopic.

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"...a pair of neuroscientists organized a symposium on newly discovered functions of the cerebellum unrelated to motor control. New experimental techniques are showing that in addition to controlling movement, the cerebellum regulates complex behaviors, social interactions, aggression, working memory, learning, emotion and more.

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"The principal type of neuron in the cerebellum, called the Purkinje cell, is widely branching like a fan coral, yet flattened and nearly two-dimensional. The fan’s blades are the neuron’s dendrites, which receive incoming signals. These flat neurons are arranged in parallel, as if millions of fan corals were stacked atop each other in a tight bundle. Thousands of tiny neurons run axons — the brain’s transmission cables for electrical impulses — perpendicularly through the stack of dendrites, like threads in a loom. Each axon connects with the dendrites of tens of thousands of Purkinje cells.

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"This circuitry, unique to the cerebellum, can crunch enormous amounts of incoming data from the senses to regulate body movement. The fluid movement of a ballerina leaping across the stage requires the cerebellum to rapidly process information from all senses while tracking the changing positions of limbs, maintaining balance, and mapping the space through which the body is moving. The cerebellum uses that dynamic information to control muscles with precise timing, and to do so in the right social context, driven by emotion and motivation.

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"I had not fully appreciated the complexity of the motor control required for speech before. The physicality includes not only the intricate gymnastics of tongue and lips — to produce sound as well as adjust pitch and volume — but also gesticulation. Our words are timed so we don’t talk over the other person, and they are regulated for the social context: infused with the proper emotion and driven by motivation, thought, anticipation and mood.

"Coordinating these diverse functions requires tapping into nearly everything the brain does — from regulation of heart rate and blood pressure, performed in deep brain regions, to the processing of sensory and emotional information, performed by the limbic system. It also requires engaging with the highest-level cognitive functions of comprehension, inhibition and decision-making in the prefrontal cerebral cortex.

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"Jessica Verpeut of Arizona State University reported data describing the intricate and expansive network of cerebellar connections that are activated throughout the brain in mice when they socialize or learn to negotiate a maze.

"Rudolph shared experiments showing that maternal behavior, studied in female mice caring for their pups, was affected by hormones acting on the cerebellum, especially the hormone oxytocin, which promotes maternal bonding. When this mechanism was disrupted experimentally, the mother no longer cared for her pups.

"Yi-Mei Yang of the University of Minnesota showed that when she disrupted certain cerebellar neurons, mice lost interest in engaging with unfamiliar mice introduced into their cage. However, they had no difficulties interacting with and remembering novel inanimate objects. This indicated a deficit in complex social-recognition memory, similar to what autistic people experience.

"In fact, the cerebellum is often smaller in autistic people, and Aleksandra Badura from Erasmus University Medical Center in Rotterdam presented new data suggesting that the cerebellum is involved in autism because it is a hub of sensory input, especially for signals related to social contexts.

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"These new, groundbreaking studies show that in addition to controlling movement, the cerebellum regulates complex social and emotional behavior. To achieve this global influence, the cerebellum must be a data-crunching hub with connections throughout the brain. No wonder it has so many neurons. To accomplish this high-order command and control on its own, it must be, in fact, a little brain."

Comment: movements occur within different emotional contexts: Sports, ballet, speech, for example. The need for cerebellar input is obvious, but it took intense biochemical research to dig it out. Not by chance.