The Neuroscience of Superfluid Thinking

Cerebellum (Latin: "little brain") in yellow. Cerebellar means "relating to the cerebellum." Cerebro-cerebellar circuits connect both cerebral hemispheres to the left and right cerebellar hemispheres.

Source: decade3d - anatomy online/Shutterstock

Until recently, the human cerebellum was viewed primarily as a brain region that's sole job was to coordinate motor movements; most neuroscientists didn't think the cerebellum facilitated non-motor cognitive functions. But around 1998, at the dawn of the 21st century, this motor-function-only view of the cerebellum started to shift. Today, most neuroscientists agree that our so-called "little brain" plays a big role in cognition.

In this post, I'm going to filter two January 2022 papers that put cerebro-cerebellar functional connectivity in the spotlight through the lens of an "up brain-down brain" model my neuroscientist father and I created in the early 2000s.

The first paper (McAfee, Liu, Sillitoe, & Heck, 2022) presents a new theory of how the cerebellum coordinates neuronal communication in the cerebral cortex. The second paper (Li et al., 2022) examines how cerebro-cerebellar connectivity between microzones of the cerebellum and specific regions of the cerebrum affects verbal fluency during language tasks.

Cerebro-Cerebellar Circuits Coordinate Fluid Motion

In the 1970s, as a rookie tennis player, Arthur Ashe and Björn Borg were my role models.

Borg was notorious for his cool (almost "icy") Swedish temperament and grace under pressure. Ashe was a trailblazer who famously said, "There's a thing in sports called, 'paralysis by analysis.'" My neurosurgeon father, who wrote The Fabric of Mind, filtered their playing styles through brain science.

When coaching me to play like Borg, Dad focused on hacking the vagus nerve by taking a deep diaphragmatic inhalation followed by a long, slow exhale before every serve. This breathing technique activated my parasympathetic nervous system and quelled fight-or-flight stress. When coaching me to play like Ashe, Dad focused on not "overthinking" by unclamping my cerebral cortex and relying on cerebellar muscle memory.

This sagittal cerebro-cerebellar diagram illustrates Bergland's split-brain model and was published in "The Athlete's Way."

Source: Photo and illustration by Chris Bergland (circa 2005)

In the mid-2000s, I wrote The Athlete's Way; and my father was the book's medical advisor. From a neuroscience perspective, our goal was to give readers a new split-brain model that would help them optimize flow states, experience superfluidity, and achieve peak performance.

Because the cerebellum has long been known to play a central role in coordinating muscle movements, we hypothesized that athletes could improve the fluidity of their motor coordination by emphasizing the importance of bottom-up processing.

On the flip side, too much top-down cerebral processing would disrupt flow and was likely to cause an overthinking athlete to choke due to "paralysis by analysis."

Notably, the cerebrum ("big brain") has two cerebral hemispheres, and the cerebellum ("little brain") has two cerebellar hemispheres. When coordinating fluid movements, the right cerebellar and left cerebral hemispheres work together to coordinate motor skills on the right side of the body and vice versa.

The criss-cross functional connectivity of "up brain-down brain" is key to creating superfluidity in sports. Interestingly, left-brain thinking also benefits from robust connectivity to the right cerebellar hemisphere, and whole-brain thinking benefits from all four brain hemispheres working in synchrony.

For example, in right-handed people who tend to have most of their language functions seated in the left cerebral hemisphere, microzones in the right cerebellar hemisphere coordinate language tasks (Li et al., 2022). During language tasks involving the left cerebral hemisphere, regions in the right cerebellar hemisphere (e.g., lobule VI, Crus I, and Crus II) are activated as part of a cerebro-cerebellar loop.

Cerebro-Cerebellar Circuits May Coordinate Superfluid Cognitive Processes

As an athlete, my interest in optimizing the functional connectivity of all four brain hemispheres was directly linked to improving my sports performance by facilitating perfectly coordinated frictionless flow (i.e., superfluidity).

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As a writer, I realized that anytime I experienced a flow state while touch typing 100+ words per minute using the cerebellar muscle memory I'd laid down in a high school typing class, my thinking also felt superfluid.

Anecdotally, as a retired ultramarathon runner who still loves to jog, I've observed that my creative thinking and writing process benefit from cardio. Fresh ideas seem to bubble up from my subconscious when I'm jogging, and it's much easier to connect the dots between seemingly unrelated ideas while performing moderate-to-vigorous physical activity.

One day, in 2009, as I was walking home from the gym, I bumped into an old friend named Maria, who's a poet, and had also just finished a workout. We started discussing how cardio workouts seemed to improve our ability to craft language. She said, "Poetry pours out of me whenever I'm on the elliptical trainer," while moving her arms and legs in a bipedal motion.

In a flash, as Maria was miming the back and forth motions of being on an elliptical, I visualized a bidirectional feedback loop between all four brain hemispheres creating a cerebro-cerebellar loop that looks like a figure 8. And I imagined how this circuitry might facilitate verbal fluency. I rushed home and drew a rudimentary "Super Eight" brain map (below).

This brain map illustrates how robust cerebro-cerebellar connectivity might facilitate superfluidity in sports and during the writing process.

Source: Photo and illustration by Chris Bergland (circa 2009)

Without explicitly referencing neuroscience, Joyce Carol Oates has vividly described how some prose captures the "fluidity of movement" and how, throughout her writing career, daily jogs have helped her "maintain a consistent, fluid voice" when writing a novel.

In a 1999 piece for the New York Times' arts section, "To Invigorate Literary Minds, Start Moving Literary Feet," Oates elucidates how running expands her consciousness and allows her to "envision what I'm writing as a film or a dream." She goes on to say:

"In running the mind flies with the body; the mysterious efflorescence of language seems to pulse in the brain, in rhythm with our feet and the swinging of our arms. The structural problems I set for myself in writing, in a long, snarled, frustrating, and sometimes despairing morning of work, for instance, I can usually unsnarl by running in the afternoon."

Cerebellar Dysfunction Can Cause Uncoordinated Thinking

Jeremy Schmahmann's Dysmetria of Thought hypothesis posits that a well-functioning cerebellum can coordinate thoughts much like it coordinates movements.

Conversely, a dysfunctioning cerebellum can cause uncoordinated movements or, in some cases, discombobulated thinking. Schmahmann is a neurologist and cerebellar ataxia specialist at Harvard Medical School's Mass. General Hospital. Ataxía means "lack of coordination" in Greek.

In the late 20th century, Schmahmann noticed that some patients with damage to specific microzones of the cerebellum didn't display physical ataxias but seemed to have trouble coordinating their thoughts.

In 1998, Schmahmann coined the term "dysmetria of thought." The same year, he published a landmark paper describing cerebellar cognitive affective syndrome (CCAS). At the time, it was a radical notion to speculate that the cerebellum was involved in non-motor functions such as cognition.

Flash forward to 2022. We now have increasing evidence that the cerebellum plays a significant role in coordinating cognitive processes.

Figure 1. (A) Cerebro-cerebellar interaction via reciprocal connections between specific cerebral and cerebellar areas. (B) Cerebellar modulation of communication between cerebral cortical areas. Here, the cerebellum coordinates communication by augmenting the coherence of neuronal oscillations in a task-specific manner.

Source: McAfee, Liu, Sillitoe, and Heck/Creative Commons Attribution License (CC BY)

In their January 2022 open-access paper, "Cerebellar Coordination of Neuronal Communication in Cerebral Cortex," first author Samuel McAfee et al. explain how the cerebellum coordinates and optimizes cerebral cortical communication during cognitive processes much like it optimizes motor coordination. Their Figure 1 illustration (above) shows these cerebro-cerebellar functions in action.

Moving forward, we need more research to better understand how cerebro-cerebellar connectivity coordinates fluid thinking.