Cerebral Hemispheres 2
NEUROSCIENTIFICALLY CHALLENGED

NEUROSCIENCE MADE SIMPLER

Know your brain: Cerebellum


Where is the cerebellum?

Cerebellum (in green)

The cerebellum is hard to miss when you're looking at a brain. Cerebellum is Latin for "little brain", and indeed the cerebellum looks a bit like a smaller version of our brain. It protrudes from the back and bottom of the cerebral cortex. You can see it when looking at a side view of a brain as the most posterior and inferior portion of the brain (see picture to the right).


What is the cerebellum and what does it do?

Although the cerebellum is involved in a number of brain functions, it is best known for its part in the modulation of movement. When we make a voluntary movement, the signal to initiate that movement originates in the motor cortices. Before the signal is sent to our muscles, however, it is sent to the cerebellum.

In addition to receiving information about the planned movement from the cortex, the cerebellum also gets information about the position of the body from the spinal cord. It uses this information to coordinate the movement and allow us to make it in a smooth manner, while maintaining our balance and equilibrium.

For example, imagine you are standing up and there is a piece of cake on the table in front of you. A plan to reach for the cake originates in the motor cortex. But, in order for that plan to result in a fluid movement, a number of things have to happen. For example, the movement must be executed with the current position of the body in mind. If you are standing stably on two feet, the action would require a different motor plan than if you were trying to balance on one foot. Also, muscles that oppose the movement must be inhibited; otherwise your attempt to extend your arm might be negated by the muscles whose role is to flex your arm. When the cerebellum receives information about the motor plan from the motor cortex, it incorporates what it knows about the position of the body and muscles; then it sends the plan back to the cortex to put it into action.

Watch this 2-Minute Neuroscience video to learn more about the cerebellum.

As you reach for the cake, however, there will also be a number of small corrections that must be made along the way. Although to us our movements seem like they are made up of large components (e.g. reaching, grasping), in the brain they are actually made of up very small increments. The plan for each increment is developed based on the results of the previous one. In other words, when you reach for the cake your brain is constantly getting data about the position of your hand and arm in real-time and using that data to make minor adjustments to the movement as it occurs.

Thus, the movement of our arm is made up of a number of smaller movements that involve slight deviations and then a return to the originally designated course. It is similar to the approach an airplane uses to get from, for example, New York to San Francisco. Although the course between the two cities seems to be straightforward, due to variables like wind and weather the route will never be exactly the same. When any particular trip is examined closely, one will see that the plane frequently deviated and then returned to its path. Similarly, your brain must get information about where your arm is in space and, if it is not on the mark in reaching for the cake, the path must be corrected.

These corrections are happening on the order of milliseconds, and so we are not aware of them, but the cerebellum is essential to making them happen. When the cerebellum detects any potential deviations from the route originally planned, it uses that information to send a modified plan back to the motor cortex. This corrected plan is what is used to generate the next increment of movement in reaching for the cake.

In this way, the cerebellum provides an error detection and correction mechanism. This allows our movements to appear smooth, precise, and coordinated. The importance of the cerebellum in facilitating smooth movement can especially be seen in someone who has experienced cerebellar damage. They may develop cerebellar ataxia, which involves problems not in the initiation, but in the execution, of movement. Their movements may be abnormally timed, jerky, and riddled with tremors.

The cerebellum also seems to be important to the learning of motor movements. When we repeat a motor movement over and over again, we gradually learn to execute it more smoothly and precisely. This learning process is based in part on the strengthening of synapses in the cerebellum.

Someone who experiences cerebellar damage (e.g. through a stroke) may also display cognitive and emotional disturbances or deficits. Thus, there appears to be more to the cerebellum than just its role in movement. However, due to the distinctive movement disorders that appear when someone experiences cerebellar damage, its capacity to promote smooth and coordinated movement is what the cerebellum is best known for.


Reference:

Nolte J. The Human Brain: An Introduction to its Functional Anatomy. 6th ed. Philadelphia, PA. Elsevier; 2009.

YOUR BRAIN, EXPLAINED

Sleep. Memory. Pleasure. Fear. Language. We experience these things every day, but how do our brains create them? Your Brain, Explained is a personal tour around your gray matter. Building on neuroscientist Marc Dingman’s popular YouTube series, 2-Minute Neuroscience, this is a friendly, engaging introduction to the human brain and its quirks using real-life examples and Dingman’s own, hand-drawn illustrations.

  • ...a highly readable and accessible introduction to the operation of the brain and current issues in neuroscience... a wonderful introduction to the field. - Frank Amthor, PhD, Professor of Psychology, The University of Alabama at Birmingham, author, Neuroscience for Dummies

  • Reading like a collection of detective stories, Your Brain, Explained combines classic cases in the history of neurology with findings stemming from the latest techniques used to probe the brain’s secrets. - Stanley Finger, PhD, Professor Emeritus of Psychological & Brain Sciences, Washington University (St. Louis), author, Origins of Neuroscience

  • Dingman weaves classic studies with modern research into easily digestible sections, to provide an excellent primer on the rapidly advancing field of neuroscience. - Moheb Costandi, author, Neuroplasticity and 50 Human Brain Ideas You Really Need to Know

  • An informative, accessible and engaging book for anyone who has even the slightest interest in how the brain works, but doesn’t know where to begin. - Dean Burnett, PhD, author, Happy Brain and Idiot Brain

BIZARRE

This book shows a whole other side of how brains work by examining the most unusual behavior to emerge from the human brain. In it, you'll meet a woman who is afraid to take a shower because she fears her body will slip down the drain, a man who is convinced he is a cat, a woman who compulsively snacks on cigarette ashes, and many other unusual cases. As uncommon as they are, each of these cases has something important to teach us about everyday brain function.

  • Dingman brings the history of neuroscience back to life and weaves in contemporary ideas seamlessly. Readers will come along for the ride of a really interesting read and accidentally learn some neuroscience along the way. - Erin Kirschmann, PhD, Associate Professor of Psychology & Counseling, Immaculata University

  • A unique combination of storytelling and scientific explanation that appeals to the brain novice, the trained neuroscientist, and everyone in between. Dingman explores some of the most fascinating and mysterious expressions of human behavior in a style that is case study, dramatic novel, and introductory textbook all rolled into one. - Alison Kreisler, PhD, Neuroscience Instructor, California State University, San Marcos

  • Bizarre is a collection of stories of how the brain can create zombies, cult members, extra limbs, instant musicians, and overnight accents, to name a few of the mind-scratching cases. After reading this book, you will walk away with a greater appreciation for this bizarre organ. If you are a fan of Oliver Sacks' books, you're certain to be a fan of Dingman's Bizarre. - Allison M. Wilck, PhD, Researcher and Assistant Professor of Psychology, Eastern Mennonite University

  • Through case studies of both exceptional people as well as those with disorders, Bizarre takes us on a fascinating journey in which we learn more about what is going on in our skull. - William J. Ray, PhD, Emeritus Professor of Psychology, The Pennsylvania State University, author, Abnormal Psychology