Cerebro-Cerebellar Circuits Remind Us: To Know Is Not Enough

Early 20th-century anatomical illustration of the human brain (from below) showing the left and right hemispheres of both the cerebellum and cerebrum. "Cerebellar" is the sister word to "cerebral" and means 'relating to or located in the cerebellum.' "Cerebro-Cerebellar" generally refers to the functional connectivity and interplay between regions of the cerebrum and regions of the cerebellum.

Source: Wikipedia/Public Domain

About ten years ago, I was walking home from the gym and had a random encounter with an acquaintance that changed how I think about the human brain. Back in 2009, I was working on a book proposal, “The Origins of Imagination,” which explored the neuroscience of creative breakthroughs based primarily on anecdotal evidence of people having “Eureka!” or “Aha!” moments while doing some type of bipedal, aerobic activity. (e.g., Albert Einstein said of E = mc², “I thought of that while riding my bicycle.”)

My hypothesis was that engaging the cerebellum (Latin for "little brain") by walking, jogging, biking, etc. was a universally accessible way to "unclamp*" the prefrontal cortex, which encouraged ideas that had been incubating somewhere in the subconscious to “bubble up” into conscious awareness. (*In the "The Gospel of Relaxation," William James famously said, "Unclamp, in a word, your intellectual and practical machinery, and let it run free; and the service it will do you will be twice as good.")

Yes, I know. My hypothesis about ideas "bubbling up from the subconscious" doesn’t sound very scientific. But, I had a hunch based on extensive conversations with my late father, Richard Bergland (1932-2007), who was a neuroscientist and author of The Fabric of Mind, that the interplay between the cerebrum and cerebellum might have something to do with the creative process.

My father died of a heart attack in 2007, just a few weeks after my first book had been published. In my mind’s eye, I often imagine my father on his deathbed saying to me, “Chris, we still don’t know exactly what the cerebellum is doing. But, whatever it’s doing, it’s doing a lot of it. Can you keep your antennae up for state-of-the-art research on the cerebellum to help solve this riddle after I’m gone?” Since his death, I've done my best to continuously report on new cerebellar research and am constantly thinking about what the cerebellum is doing.

In 2005, my dad and I created a father-son, split-brain model we called “up brain-down brain” as the foundation for my book, The Athlete’s Way. Our split-brain model basically framed the cerebrum as the seat of explicit learning, mindset, and declarative memory; and framed the cerebellum as the seat of implicit learning, "knowing-without-knowing," and Purkinje-based muscle memory. (For more on this see, “The Split-Brain: An Ever-Changing Hypothesis.")

Back in the 1970s, my father had lost some credibility among his Harvard Medical School peers when he served as the medical expert for a bestselling book called Drawing on the Right Side of the Brain, which became part of the left brain-right brain juggernaut, which is still a ‘pseudoscience’ runaway train almost 50 years later.

Our goal with the "up brain-down brain" model was to shift the focus away from left brain-right brain lateralization of the cerebral hemispheres and focus more on the “upstairs-downstairs” interplay between the cerebrum and cerebellum. I also wanted to start a discussion in a public forum that would help debunk "the right brain is the seat of creativity” myth with the additional hope of vindicating my father's reputation. Needless to say, getting the right brain-left brain genie back in the bottle is a daunting task.

My “Origins of Imagination” book proposal from 2009 put the cerebellum in the spotlight as an underestimated and unrecognized player in cognitive processes, fluid intelligence, and divergent thinking. (Unfortunately, none of the “Big Five” publishers were interested in this book ten years ago, and my agent couldn’t sell the proposal.)

Getting back to my random encounter a decade ago that changed how I think about the brain... One day in 2009, I was walking home from the gym on Commercial Street in Provincetown, Massachusetts when I bumped into my friend Maria who is a poet. She asked me, “What are you up to these days?” I told her about the aforementioned concept for the “Origins of Imagination” book. As we stood there, Maria started moving her body to emulate riding an elliptical machine and said, “Whenever I start moving my arms and legs back and forth on the elliptical trainer, poetry pours out of me.”

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As I stood on the sidewalk watching Maria mime doing an aerobic workout, I had a “Eureka!” moment that both the ‘left brain-right brain’ and 'up brain-down brain’ split-brain models were partially correct in terms of physical activity facilitating fluid intelligence and creative thinking.

In a contralateral, crisscross manner, the left cerebral hemisphere works in conjunction with the right cerebellar hemisphere to coordinate movement on the right side of the body; and the “right brain” of the cerebrum works with the left hemisphere of the cerebellum to coordinate voluntary movements on the left side of the body. In terms of the entire brain working in concert, optimizing the structure and functional connectivity of all four brain hemispheres is key.

As is often the case, after months of cramming my head full of crystallized knowledge and empirical evidence, the “aha!” moment of finally connecting seemingly unrelated ideas into something potentially new and useful was triggered by a random and serendipitous circumstance. I told Maria that hearing her say “Whenever I start moving my arms and legs back and forth on the elliptical trainer, poetry pours out of me,” had given me a new idea. Then, I rushed home to scribble down the rudimentary “brain map” sketch you see below:

This topographical brain map of "cerebro-cerebellar" circuitry illustrates the importance of optimizing the contralateral functional connectivity between both cerebral hemispheres and both cerebellar hemispheres.

Source: Photo and illustration by Christopher Bergland circa 2009

When I sketched this very basic “topographical brain map” a decade ago, I was completely unaware of the term “cerebro-cerebellar” and had no crystallized knowledge of Jeremy Schmahmann's groundbreaking “Dysmetria of Thought” hypothesis and his identification of the “Cerebellar Cognitive Affective Syndrome" (CCAS). The child-like illustration above drawn with multi-colored Sharpies and fluorescent markers is the result of me cobbling together random anecdotal evidence, personal life experiences, and having lots of conversations about the cerebrum and cerebellum with my dad.

Now that I've spent much more time fastidiously studying neuroscience, I know that Schmahmann published a landmark paper, “The Cerebrocerebellar System,” in 1997 which laid the groundwork for decades of subsequent research on the interplay between the left and right hemispheres of the cerebrum and cerebellum. For example, yesterday I wrote a Psychology Today blog post about a new study, “Cerebro-Cerebellar Functional Connectivity is Associated with Cerebellar Excitation-Inhibition Balance in Autism Spectrum Disorder."

This is how Schmahmann described "The Cerebro-Cerebellar System" in 1997:

If there is a cerebellar contribution to nonmotor function, particularly to cognitive abilities and affective states, then there must be corresponding anatomic substrates that support this. The cerebellum is strongly interconnected with the cerebral hemispheres in both feedforward (cerebral hemispheres to cerebellum) and feedback directions. This relationship has long been recognized, particularly with respect to the motor and sensory cortices. Investigations performed over the last decade, however, have demonstrated for the first time the organization and strength of the connections that link the cerebellum with areas of the cerebral cortex known to be concerned with higher order behavior rather than with motor control."

At this stage of life, I dedicate most of my time to cerebral pursuits. I spend a few hours every day reading and writing about science-based empirical evidence. That being said, when it comes to reporting on neuroscience and learning more about the cerebellum, it's clear to me that there is some truth in the axiom: "The more you know, the less you understand."

For example, with Google Scholar at my fingertips, I can spend copious amounts of time reading in-depth scientific studies about something like cerebellar Purkinje cells. But, at a certain point, this type of information overload creates alphabet soup in my brain and is counterproductive. Having too much crystallized knowledge crammed into my head at one time without giving the ideas time to gestate creates viscosity of thought and stifles what I call "superfluidity."

Whenever I find myself overthinking or suffering from what Arthur Ashe called "paralysis by analysis," it's always helpful to do something more cerebellar (like going for a long jog) and spacing out for a while. Performing cerebellum-based activities seems to "unclamp" specific regions in my cerebral cortex in a way that helps me think better and problem solve.

My Alma Mater’s Motto Is: Non Satis Scire (“To Know Is Not Enough”)

One reason I decided to write a first-person narrative blog post this morning is that my life story and transition from being a professional athlete to a science writer unearths some fundamental aspects of the brain mechanics that drive our cerebro-cerebellar circuitry.

My father was a “cerebral” powerhouse who got straight A's and was always top of his class. He also had the “cerebellar" athletic prowess to be a tennis champion. Dad expected the same level of academic and sports achievement from his kids. Unfortunately, through the lens of cerebro-cerebellar circuitry, my older sister and I were only “half-brained” in terms of living up to dad's unrealistic expectation that all of his school-aged children would display extraordinary cerebral and cerebellar abilities.

My older sister had incredible “book smarts” and got National Merit SAT scores, but wasn’t particularly good at playing tennis. On the flip side, I was terrible in school (and was probably viewed by many as a “dumb jock”) but was good at sports. One reason I decided to publish a book after retiring from athletic competitions was to prove to my father (and other naysayers) that neuroplasticity and neurogenesis allow each and every one of us to beef up our cerebral-cerebellar structure and functional connectivity at any stage of life—which was the entire point of The Athlete’s Way: Sweat and the Biology of Bliss.

As the father of a 10-year-old now, it’s important to me that my daughter’s education and day-to-day life is well-rounded in a way that optimizes her cerebro-cerebellar circuitry.

Looking back on my academic experiences growing up, I was very fortunate to attend schools that unwittingly nurtured a healthy balance between my cerebrum and cerebellum. I was also lucky to spend some time trapped in an academic institution that only seemed to care about forcing students to sit still in class, memorize mountains of crystallized knowledge, and get high test scores. This experience opened my eyes to the pitfalls of overemphasizing cerebral knowledge and ignoring the important role that both cerebellar hemispheres play in our cognitive and creative processes.

Source: Wikipedia/Public Domain

When I was in the seventh grade, I started taking Latin with Mr. Bourne at The Park School in Brookline, Massachusetts. Although I was generally a terrible student, I loved Latin and excelled in this subject. Mr. Bourne made learning ancient Latin seem like a surprisingly useful knowledge-base for modern times. To this day, I find myself referencing Latin words on a regular basis and the phrase "non satis scire" inspired this blog post.

After leaving the womb-like existence and "boundary-less education" pedagogy of The Park School, I was sent off to a draconian boarding school in Wallingford, Connecticut called Choate Rosemary Hall. Their motto is Fidelitas et Integritas (Fidelity and Integrity). In the early 1980s, Choate was a toxic environment for me. I didn't fit the Preppy Handbook mold and hated the place. I rebelled against the school's authoritarianism and lived by the "We don't need no education" theme of Pink Floyd's album, "The Wall." Suffice to say, my grades sucked. I had trouble with standardized tests and my SAT scores were the pits.

Source: Wikipedia/Public Domain

Luckily, my mom knew about a small liberal arts college in Amherst, Massachusetts that didn't care about SAT scores and purposely took the emphasis off cerebral "book smarts" called Hampshire College. At the time, Hampshire was one of the only colleges in the country that didn't require students to take any tests and there were no grades. It sounded like a perfect place for me and I was eager to apply.

When I enrolled at Hampshire College in the fall of 1984, my declarative memory knew the school's motto was Non Satis Scire (To Know Is Not Enough). But, I realize now, I didn't really know (in the truest sense of the word) why my Alma mater's motto was so important until decades later when I retired from being a professional ultra-endurance athlete and became a science-based writer.

From a meta-cognitive perspective of "thinking about one's thinking," it isn't lost on me that knowing the meaning of the Latin words for "to know is not enough" is much different than realizing the significance of how this phrase applies to our cognitive processes in a digital age. Long before the internet revolution, the founders of Hampshire College realized that "knowing" lots of crystallized information is useless if you can't connect the dots of seemingly unrelated ideas in new and useful ways.

In a Google-search era, we have so much crystallized knowledge at our fingertips 24-hours a day. This abundance of cerebral information makes it more important than ever to keep the cerebellum engaged by staying physically active. Sedentarism and sitting in front of a computer screen all day may cause the gray matter volume of Purkinje cells in the cerebellum to atrophy and can reduce the integrity of white matter tracts between various brain regions. This double whammy prevents all four brain hemispheres from working in perfect harmony and could result in lower cerebro-cerebellar functional connectivity.

I strongly believe that finding everyday ways to optimize the functional connectivity of our cerebro-cerebellar circuitry is key to divergent thinking and fluid intelligence. As the founders of Hampshire College realized decades ago, "To know (crystallized information) is not enough." Hopefully, in the years ahead, more educators will realize the importance of structuring learning environments that actively engage all four brain hemispheres and strive to optimize students' cerebro-cerebellar functional connectivity on a daily basis.