This is the cerebellum, which is located at the back of the brain and is dubbed the “little brain” after its Latin name.
Textbooks and encyclopedias emphasize how the cerebellum regulates movement in the body.
A symposium on the recently identified roles of the cerebellum unrelated to motor control was arranged there by two neuroscientists.
Emerging experimental methodologies are demonstrating that the cerebellum not only governs movement but also intricate behaviors, social interactions, aggression, working memory, emotion, and more.
A Breach in Dominant Wisdom Since the 19th century, it has been known that the cerebellum and movement are related.
There was no doubt that balance and movement were crucial for coordinating motion because patients who had suffered brain trauma clearly had trouble with these skills.
Scientists studying neurology have accumulated decades of experience and knowledge about how the special neural circuitry of the cerebellum regulates movement.
Neurologists then reported in the journal Brain in 1998 on a wide range of emotional and cognitive impairments in patients suffering from cerebellar damage.
It was once believed that the limbic system and cerebral cortex housed these higher order cognitive and affective processes.
It would require connections throughout the entire brain for the cerebellum to be able to do that.
Neuroanatomists can now follow those pathways throughout the entire brain, starting from the cerebellum and ending at relay points, thanks to new techniques.
These novel and innovative investigations demonstrate that the cerebellum not only modulates movement but also intricate social and affective behavior.
The cerebellum needs to be a networked hub for processing data across the entire brain in order to have this widespread impact.
It must actually be a small brain if it can perform this high-order command and control on its own.
NEUTRAL
This story’s initial publication was in Quanta Magazine.
Even with the remarkable advancements in neuroscience over the past few decades, a crucial aspect of the brain is still unknown. The term “little brain” refers to the cerebellum, which is located at the rear of the brain and resembles a bun. This is a serious error because, unlike the disorganized thicket of neurons found elsewhere in the brain, the cerebellum contains three-quarters of all the neurons. These neurons are arranged in an almost crystalline fashion.
Textbooks and encyclopedias emphasize how the cerebellum regulates movement in the body. There is no denying the cerebellum’s role in this. However, scientists now believe that this conventional wisdom is limited in scope.
Or so I discovered in November while attending the largest gathering of neuroscientists worldwide—the Society for Neuroscience annual meeting—in Washington, DC. There, two neuroscientists hosted a symposium on recently identified cerebellar functions unrelated to motor control. Recent studies have demonstrated that the cerebellum not only regulates movement but also intricate behaviors, social interactions, aggression, working memory, emotion, and learning.
A Breach of Predominant Wisdom.
Since the 1800s, it has been known that the cerebellum and movement are related. It was evident from the movement and balance problems of brain trauma patients that the brain region was essential for motor coordination. The distinct neural circuitry of the cerebellum regulates motor function, and neuroscientists have gained a thorough understanding of this process over the years. The cerebellum’s functioning was explained in a very detailed manner.
Then, in the journal Brain in 1998, neurologists reported on a wide range of emotional and cognitive impairments in patients suffering from cerebellar damage. A tumor in the cerebellum was discovered by a CT scan of a 22-year-old female college student who had fallen during an ice skating session in 1991. She was a totally different person after having it surgically removed. The intelligent college student could no longer copy a basic diagram, name common objects, do mental arithmetic, or write well. Her attitude soured. She concealed herself under blankets and acted badly, taking off her clothes in the hallways and using baby language. Her ability to interact socially, including identifying familiar faces, was also compromised.
The writers were baffled by this case and others like it. It was once believed that the limbic system and cerebral cortex housed these higher order cognitive and affective processes. “It’s still unclear exactly what the cerebellum’s function is and how it’s carried out,” they said in their conclusion.
Leading experts continued to maintain that the cerebellum’s role was limited to controlling movement in spite of indications from clinical research that the traditional understanding was incorrect. Diasynou Fioravante, a neurophysiologist at UC Davis who co-organized the conference symposium, said, “It is kind of sad, because it has been 20 years since these cases were reported.”.
The neuroscientist Stephanie Rudolph of Albert Einstein College of Medicine, who co-organized the symposium with Fioravante, claimed that other neurologists had long observed neuropsychiatric deficits in their patients. Nevertheless, the clinical reports were disregarded because there was no conclusive anatomical evidence for how the cerebellum’s distinct neural circuitry could potentially regulate the stated psychological and emotional functions.
Currently, a deeper comprehension of the cerebellum’s electrical architecture is validating those case studies and refuting conventional wisdom.
With accuracy in wiring.
Three-quarters of the brain’s neurons are concentrated into a 4-inch lobe due to the exact organization and compression of the cerebellum’s wiring pattern. The Purkinje cell, the main kind of neuron in the cerebellum, is somewhat two-dimensional and flattened, with many branches resembling a fan coral. The dendrites of the neuron, which receive incoming signals, are like the blades of a fan. These parallel arrangements of flat neurons give the impression that millions of fan corals are tightly bunched up on top of one another. Axons, the brain’s electrical impulse transmission cables, are threaded, like threads in a loom, by thousands of microscopic neurons that run perpendicularly through the stack of dendrites. Tens of thousands of Purkinje cells, each with an axon connected to its dendrites.
The 50 billion neurons that make up the cerebellum have an incredible capacity for integration because of this degree of interconnectivity. The cerebellum’s special circuitry is responsible for processing massive amounts of sensory data to control movement. The cerebellum must quickly process information from all senses in order to track limb changes, maintain balance, and map the space that the body is moving through during a ballerina’s fluid leap across the stage. The cerebellum uses this dynamic information, motivated by emotion and motivation, to precisely time the contraction and release of muscles in the appropriate social context.
Neuroscientists are now beginning to realize, according to Fioravante and Rudolph, that the cerebellum’s potent neural circuitry, which integrates information for bodily movement, also enables it to manage intricate mental processes and behaviors.
For instance, Rudolph said during our conversation prior to the symposium starting, “You ask questions, and we give answers.”. That conduct is intricate. She had to listen to what I was saying, think of a way to respond, and then use her muscles to speak. She also needed to read my nonverbal cues and other small signs. She said, “For example, I can tell you are listening and interested because you are nodding right now.”.
I had not before realized how intricate the motor control needed for speech was. The physicality involves gestures in addition to the complex lip and tongue maneuvers used to produce sound and modify pitch and loudness. Our words are regulated for the social context, appropriately charged with emotion, and influenced by motivation, thought, anticipation, and mood. We time them so as not to interrupt the other person.
Accessing almost every aspect of the brain’s capabilities is necessary to synchronize these various processes, ranging from the limbic system’s processing of sensory and affective data to deep brain regions that control blood pressure and heart rate. Encouraging comprehension, inhibition, and decision-making at the highest cognitive levels in the prefrontal cerebral cortex is also necessary.
The cerebellum would need to be connected throughout the brain in order to perform that function. There hasn’t been much evidence for that up until now, but new methods are revealing these pathways.
a center for sensory input.
When neuroanatomists first mapped the brain decades ago, they were unable to identify any direct connections between the cerebellum and limbic system and prefrontal cortex—two brain regions that regulate emotion and thought. They concluded from this that the cerebellum was largely separate from and unrelated to these higher order cognitive processes. Neural signals, however, can jump from one neuron to the next, much like thieves might avoid a tracker by switching vehicles. Neuroanatomists were sidetracked from studying the cerebellum by this covert activity.
These pathways originate in the cerebellum and can be traced across relay points and throughout the brain by neuroanatomists thanks to new techniques. For instance, scientists can insert rabies viruses into neurons to precisely observe which other neurons they make contact with. To see the flow of information in neural circuits, scientists have genetically modified fluorescent proteins to flash when a neural impulse fires. They can also follow the traces left by neuronal activity: when a particular behavior is carried out in a neural network, the appearance of proteins generated by firing neurons can be used to identify all the cells that are communicating with one another.
Researchers presented an array of exciting new discoveries at the symposium, illustrating their growing understanding of the cerebellum and made possible by these innovative techniques.
Data described by Jessica Verpeut of Arizona State University show that when mice socialize or learn to navigate a maze, a complex and wide-ranging network of cerebellar connections is activated throughout the brain.
Rudolph presented research demonstrating the impact of hormones acting on the cerebellum, particularly the bonding hormone oxytocin, on the behavior of mother mice raising their young. The mother stopped giving her pups any care after this mechanism was experimentally interfered with.
Researchers Yi-Mei Yang of the University of Minnesota demonstrated that mice lost interest in interacting with new mice that were placed in their cage when she interfered with specific cerebellar neurons. On the other hand, they had no trouble interacting with and recalling unfamiliar inanimate items. This suggested a deficiency in sophisticated social-recognition memory, akin to that observed in autistic individuals.
As a hub of sensory input, particularly for signals pertaining to social contexts, the cerebellum may indeed play a role in autism, as Aleksandra Badura of Erasmus University Medical Center in Rotterdam presented new data supporting this theory. In fact, the cerebellum is often smaller in individuals with autism.
This new study goes beyond experiments on mice. German clinical test developer Andreas Thieme demonstrated a novel method for precisely diagnosing emotional and cognitive deficits brought on by cerebellar damage.
These recent, ground-breaking studies demonstrate that the cerebellum not only controls movement but also intricate social and emotional behavior. The cerebellum needs to be a data-crunching hub with connections throughout the brain in order to have this widespread impact. It makes sense that it has so many neurons. Indeed, it must be a little brain if it can perform this high-order command and control on its own.
This article is reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation. Its goal is to improve public understanding of science by reporting on trends and new developments in mathematics, the physical and biological sciences, and research developments in these fields.
