Song of the Cerebellum

Summary

Radiolab – "Song of the Cerebellum" (January 30, 2026)

Episode Overview

This episode, hosted by Lulu Miller and Latif Nasser, follows science journalist Rachel Gross’s journey after an unexpected stroke damaged her cerebellum. Initially dismissed as a “motor coordination” issue by doctors, Gross’s subsequent struggles—and her deep dive into neuroscience—reveal a revolutionary understanding of the cerebellum. The episode explores how this “little brain,” long considered responsible only for movement, actually plays a much vaster and more intimate role in shaping our cognition, emotions, and very sense of self.

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Key Discussion Points and Insights

1. Rachel Gross’s Story: The Personal Becomes Universal

• The Incident ([01:15]–[04:31])

  • Rachel Gross describes losing her ability to sing karaoke and feeling off in other physical and cognitive ways. She recounts her stroke, the diagnosis of a cerebellar cavernoma, and subsequent surgery.
    • “The notes weren’t translating from my brain to my vocal cords.” — Rachel Gross [02:51]
    • Struggles included slurred speech, illegible handwriting, trouble running, and an inability to fill out her hospital admission form.

• Dismissal of Cerebellar Damage ([05:12]–[06:07])

  • Surgeons reassured her the cerebellum was “redundant” or even “practically vestigial,” likening its removal to losing an appendix.
    • “You can actually take out, like, a third of it, and people don’t even notice.” — Neurosurgeon (via Rachel Gross) [05:41]
  • Despite reassurances, Rachel experienced ongoing issues: slurred speech, timing problems, emotional dysregulation, and changes in her sense of self.

2. Cerebellum Science: From Motor Control to Cognition

• Traditional View ([09:25]–[12:41])

  • The cerebellum (Latin for “little brain”), long considered merely a movement-coordination center, was ignored in most recent neuroscience, often even cropped out of MRIs.
    • “There are MRI machines that don’t cover the cerebellum.” — Rachel Gross [12:19]

• A Paradigm Shift ([12:41]–[16:47])

  • Neurologist Jeremy Schmahmann describes a “complete paradigm shift” in cerebellum science, sparked in part by findings that links exist between cerebellum and upstairs (“thinky”) portions of the brain.
    • “Where we are now is a complete paradigm shift. There’s been a revolution in our thinking about the cerebellum.” — Jeremy Schmahmann [12:57]

• The Human Connection ([16:47]–[19:27])

  • Evolutionary biologist Robert Barton reveals that, evolutionarily, the cerebellum expanded disproportionately in apes and humans compared to other primates.
    • “In the human brain today, although [the cerebellum] is a lot smaller than the neocortex, it has about four times more neurons.” — Robert Barton [18:44]
    • “The cerebellum has about 80% of the brain cells that we have.” — Jeremy Schmahmann [18:58]

• What’s It Really Doing? ([19:55]–[28:57])

  • The cerebellum isn’t just moving muscles—it organizes, sequences, and fine-tunes everything, from grabbing a coffee cup to constructing sentences and regulating emotion.
    • “The cerebellum is also the invisible conductor of your thinking.” — Rachel Gross [27:19]
    • It helps regulate emotional “overshoot and undershoot”—both the physical clumsiness and social/emotional gaffes can emerge from cerebellar damage.
    • Rachel personally attests: “I have to manually do all these things that used to be unconscious and in the background.” [29:24]

3. Rethinking Brain and Identity

• Movement, Thinking, and the Self ([30:07]–[31:18])

  • The Western idea that “thinking” and “moving” are separate is deeply outdated.
    • “Thinking is intrinsically related to the way we move around in the world. … They’re continuous with each other.” — Robert Barton [30:07]

• Cerebellum as the Unseen, Underappreciated Hero ([31:18])

  • “I think of the cerebellum as the Cinderella of brain structures… Well, it’s time Cerebella came to the ball.” — Robert Barton [31:18]

• Rachel’s Emotional Response ([32:00])

  • Knowing the science brings both comfort and grief: “It’s kind of forcing me to dwell on what I have lost, which is this effortless, like, fluidity that I didn’t even realize I had.” — Rachel Gross [32:00]

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4. The Plastic Brain: Learning, Recovery, and Motivation

• The Importance of Motivation for Neuroplasticity ([33:41]–[34:29])

  • Neuroscientist David Eagleman emphasizes motivation as the key to brain recovery: “You need the right cocktail of neurotransmitters there for plasticity to happen, and that generally maps onto motivation.” — David Eagleman [34:08]
  • For Rachel, this means karaoke, not tuba: “What I realized was I’m already doing this with karaoke … I practiced at home. I recorded myself. I took voice lessons.” [34:29]

• Karaoke Recovery and the Many Facets of Performance ([36:07]–[37:35])

  • Speech pathologist Alison Hilger highlights the cerebellum’s vast role in singing (breath, vocal fold tension, timing, emotional nuance, audience interaction).
    • “Singing is actually the most complicated, most coordinated movement you will ever do in your body.” — Alison Hilger [36:12]
  • Rachel realizes: “It was in that fluidity and that ease that I felt in those moments that my sense of self was emerging.” [37:35]

• Loss, Adaptation, and Finding Community ([37:57]–[39:52])

  • Despite the grief of lost fluidity, Rachel finds meaning in community and acceptance—joining a choir for stroke survivors, letting go of old notions of control, and appreciating connection in whatever form is possible.

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Notable Quotes & Memorable Moments

• The Beginning: Karaoke Gone Wrong ([02:20])
  • “It was really at the chorus that just, like, nothing came out of my mouth. It was just air.” — Rachel Gross
• Surprised by the Brain’s Complexity ([18:58])
  • “The cerebellum has about 80% of the brain cells that we have.” — Jeremy Schmahmann
• Paradigm Shift in Science ([12:57])
  • “Where we are now is a complete paradigm shift. There’s been a revolution in our thinking about the cerebellum.” — Jeremy Schmahmann
• Invisible Organizer ([27:19])
  • “The cerebellum is also the invisible conductor of your thinking.” — Rachel Gross
• Sense of Self and Loss ([32:00])
  • “It’s kind of forcing me to dwell on what I have lost, which is this effortless, like, fluidity that I didn’t even realize I had.” — Rachel Gross
• On the Nature of Thinking ([30:07])
  • “Thinking is intrinsically related to the way we move around in the world.” — Robert Barton
• Motivation for Recovery ([34:08])
  • “Everything is about the motivation for it.” — David Eagleman
• Fluidity and Identity ([37:35])
  • “It was in that fluidity and that ease that I felt in those moments that my sense of self was emerging.” — Rachel Gross
• Letting Go ([39:53])
  • “You do have to let go of some of that. Let go of, like, control and this image of what you should be … and just, like, live fully in the moment that you have now.” — Rachel Gross

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Timestamps for Important Segments

| Timestamp | Segment & Topic | |-------------|---------------------------------------------------------------------| | 01:15–04:31 | Rachel’s initial symptoms, hospital visit, and diagnosis | | 05:12–06:07 | The cerebellum described as “redundant” and surgical reassurances | | 09:25–11:01 | History and traditional understanding of the cerebellum | | 12:41–16:47 | Jeremy Schmahmann on the new paradigm and anatomical evidence | | 17:04–19:27 | Robert Barton on cerebellum evolution and neuron counts | | 23:40–28:57 | Patients reveal cerebellar role in cognition, emotion, behavior | | 30:07–31:18 | Philosophical shift: movement, thinking, and the brain’s evolution | | 33:41–34:29 | David Eagleman: Recovery, motivation, and neuroplasticity | | 36:07–37:35 | Alison Hilger: Singing as cerebellum’s complexity | | 37:57–39:52 | Accepting loss, finding new community—Rachel’s choir for survivors | | 42:07–43:44 | Unexpected romance, karaoke brings new connection |

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Episode Highlights & Closing Moments

• Serendipitous Ending ([42:07–43:44])

  • Rachel receives a message from someone who saw her perform at karaoke—her “cerebellum injury-inflected” singing caught someone’s attention, leading to a romantic connection.

• Ultimate Message

  • The cerebellum is the often-overlooked “Cinderella” of the brain—intimately tied to not just movement, but thought, emotion, and selfhood.
  • Loss and recovery are intertwined, with meaning found in both striving and acceptance.

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Tone and Language

The episode balances scientific curiosity with profound empathy. Rachel Gross’s narrative is both investigative and deeply personal; hosts Lulu Miller and Latif Nasser blend playful banter with respect for the vulnerable, emotional nature of the story.

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For Listeners Who Missed the Episode

“Song of the Cerebellum” captures both the marvels of neuroscience and the mysteries still unfolding within the brain. Through Rachel Gross’s journey, listeners are challenged to rethink brain function, recognize the subtle sources of selfhood, and appreciate the hidden depths within all of us—right down to the little “Cinderella” at the base of our skulls.

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Recommended quote for reflection:

“Is the self a language that I can relearn? … If I keep pushing through that awkwardness and those moments of losing control, all these glitches and mistakes and kind of backtracking, will that ever feel like me?”
— Rachel Gross [38:57]

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For further exploration, check out Radiolab’s episode “Damn it, Basal Ganglia,” also referenced in this show.

Transcript

[Latif Nasser]

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[Latif Nasser]

Oh, wait, you're listening.

[Rachel Gross]

Okay. All right. Okay. All right.

[Robert Barton]

You're listening to Radiolab Radio from wnyc.

[Lulu Miller]

Hi, Latif.

[Latif Nasser]

Hello.

[Lulu Miller]

All right, so reporter walks into a bar.

[Jeremy Schmahmann]

Okay.

[Lulu Miller]

And that's just the beginning of our story. That reporter's name is Rachel GROSS. She is 35. The year is 2024. It's a warm spring night. The bar is in Brooklyn, and it is called the Branded Saloon.

[Rachel Gross]

So Branded Saloon is a very gay bar. You know it because there are all these rainbow flags bursting out the front. It's, like, very, very crowded and loud.

[Lulu Miller]

She's a regular. Shows up there nearly every Thursday to.

[Rachel Gross]

Hang out, like, grab some fries, hang.

[Lulu Miller]

Out for an hour, but also for karaoke. So that night she made her way.

[Rachel Gross]

To the back room, got on stage, put in, like, a Savage Garden song. Crash and Burn. From, like, my teenage years. Do you know this one?

[Lulu Miller]

I don't. Can we pull it up really quick?

[Rachel Gross]

Okay.

[Lulu Miller]

Crash and burn. Savage Garden.

[Rachel Gross]

Okay.

[Lulu Miller]

Okay, we got that. Oh, I do know this song.

[Jeremy Schmahmann]

Oh.

[Lulu Miller]

Oh, okay. Yeah. Okay.

[Rachel Gross]

So you're singing along, and I think it was initially going fine, but it's really at the chorus that just, like, nothing came out of my mouth. It was just air.

[Lulu Miller]

Could you almost imitate what happened?

[Rachel Gross]

Yeah. It goes like. When darkness is upon your door and you feel like you can't take anymore.

[Lulu Miller]

Is it like when you have a. And suddenly you're just like, oh, I can't. There's nothing coming out? Or did it feel different? Did it.

[Rachel Gross]

No, it was the notes weren't translating from my brain to my vocal cords. And the rest of the song, like, the verses, I just felt like I wasn't on the beat.

[Lulu Miller]

But you finished it out. You finished out the song.

[Rachel Gross]

Yeah. I mean, I am used to bombing. It's part of my philosophy of karaoke. It teaches you how to be okay with things not going perfectly. So I was trying to, like, keep that in mind while I was like, damn, what just happened? I literally crashed and burned.

[Lulu Miller]

And that night, when she got home, Rachel started thinking about another moment from the day that was a little strange.

[Rachel Gross]

I was, like, shadowing an acupuncturist because I was writing about alternative medicine. I'd take, like, handwritten notes, and my writing was so poor, I couldn't read it afterwards. So that was another, like, odd. But Friday, I felt myself to be slurring a bit. And then on Saturday, I decided to go for a run, and it felt really weird. It felt like I was, like, forcing my limbs to run in tandem. It was after that run that I decided I needed to go to the hospital. I remember they handed me the form that you just fill out with your basic information. And I couldn't fill out the form. Like, I couldn't write my name and birth date. Whoa. They do a CT scan, and the PA comes up to me and he's like, honey, you have a bleed in the back of your brain.

[Lulu Miller]

In other words, she'd had a stroke.

[Rachel Gross]

And that's when I went into shock.

[Lulu Miller]

So they rushed across town to a hospital that has a stroke ward.

[Rachel Gross]

There's, like, a lot of beeping. Most of the patients are over 70. Of course, the neurologist and all her residents come in, and they eventually said, we think this is a cavernoma. It's, like, where very small blood vessels form a little, like, raspberry.

[Lulu Miller]

Huh?

[Rachel Gross]

And this little raspberry can exist your whole life, but sometimes it bursts, and that's when you have a stroke. And in my case, doctors were saying you should probably have surgery to remove it.

[Lulu Miller]

And where exactly in the brain was the stroke?

[Rachel Gross]

In the cerebellum.

[Lulu Miller]

And where is that? What is that?

[Rachel Gross]

I didn't know what the cerebellum was at that point, but the neurosurgeons told me that it's in the back of my head, basically behind my neck, and it's involved in fine tuning motor stuff. They also called it redundant.

[Lulu Miller]

Redundant.

[Rachel Gross]

And later one of them called it practically vestigial.

[Lulu Miller]

It almost sounds like an appendix. Like.

[Rachel Gross]

Yeah, exactly. Exactly. Another one said, like, because I was terrified about surgery, obviously. He says, like, you can actually take out, like, a third of it, and people don't even notice what he was like, when you wake up, you might feel a little bit clumsy, but you'll still be you. Huh.

[Lulu Miller]

Was it kind of like this is of a place to have a brain situation? The cerebellum's a lucky spot.

[Rachel Gross]

Yes, yes. That was definitely, definitely reassuring because the very.

[Lulu Miller]

So Rachel went into surgery. They removed a piece of her cerebellum, and then when she woke up, she started, like, testing herself.

[Rachel Gross]

So I drew a spiral, and it was smooth, and it didn't tremor or whatever. Within a few more days, I was, like, circling the hall by myself, and nurses were, like, clapping for me. So I was like, I'm gonna have the best recovery they've ever seen.

[Lulu Miller]

So you're like, writing check. Walking check.

[Rachel Gross]

Yeah, yeah, yeah.

[Lulu Miller]

Like, stuff's coming back.

[Rachel Gross]

You're like, okay, yeah.

[Lulu Miller]

But over the next couple of months.

[Rachel Gross]

I could just still hear that slur so much. It bothered me so much. And I tried singing along to a couple karaoke tracks, and I couldn't get the timing right, let alone the notes. But then the other experience I was having was a sentence that I want to say will just kind of disappear or escape me, and I will laugh at something, but it'll come out, like, too big or too, like, rambunctious. It felt much more profound than, dear having some body coordination issues. That's, like, kind of what I'm trying to figure out now.

[Lulu Miller]

So Rachel Gross is actually a science journalist, and she writes a lot, really beautifully about the body, right?

[Latif Nasser]

Yeah, yeah, yeah. I know her work.

[Lulu Miller]

Yeah. She wrote this awesome book called Vagina Obscura.

[Latif Nasser]

Terrific book.

[Lulu Miller]

And so when she told me she wanted to talk, I figured she was going to tell me a story full of fun facts about this other body part. But as we sat there talking, I.

[Rachel Gross]

Need to just go for the nearest word.

[Lulu Miller]

It became clear she was in the middle of a story.

[Rachel Gross]

That's a difficult thing to accept for someone who's, like, used to writing. Precisely.

[Lulu Miller]

It was still unfolding.

[Rachel Gross]

There's this confrontation with your sense of, like, who you think you are.

[Lulu Miller]

So I guess, like, what do you really want to know? What are you after? What do you want to find out?

[Rachel Gross]

I think the simple quest is I want to figure out how to get my karaoke back. But that's not the bigger thing. I think my question now is, why does this feel like more than just a motor problem, more than just fine tuning? Why do I not feel like myself anymore?

[Lulu Miller]

So after that conversation, Rachel just started digging in, researching, talking to so many people, reading so many studies. Producer Sindhu nyana Sambandan and I joined whenever we could.

[Latif Nasser]

Yeah.

[Lulu Miller]

And what Rachel discovered is something I thought we were done finding, which is something totally new about the basic anatomy of the brain and a shift in how we think not just about this part of the brain, but really about thinking itself.

[Latif Nasser]

All right. Okay. This is Radiolab. Here we go.

[Lulu Miller]

Here we go.

[Rachel Gross]

Okay. So I started in kind of the most obvious place. What do we know about the cerebellum?

[Jeremy Schmahmann]

So cerebellum is the old Latin term for little brain.

[Lulu Miller]

Little brain.

[Ira Flatow]

Okay.

[Jeremy Schmahmann]

And it's tucked in under the big brain sitting in the back of the brain.

[Rachel Gross]

So I ended up calling this scientist named Jeremy Schmalman.

[Jeremy Schmahmann]

I'm a neurologist at Mass General Hospital.

[Rachel Gross]

He's been studying the cerebellum four decades now. His whole career.

[Jeremy Schmahmann]

Yeah.

[Rachel Gross]

So can we just back up? And what does it look like?

[Jeremy Schmahmann]

Well, it's smaller than the rest of the brain in terms of size.

[Rachel Gross]

It's about the size of your fist.

[Jeremy Schmahmann]

But it's very deeply folded, unlike the big folds of the cerebral hemispheres. Everybody knows those pictures. The cerebellum has multiple tiny little folds.

[Rachel Gross]

And it even lives in its own, like, membrane pocket. So it really looks like a little brain underneath the big brain.

[Jeremy Schmahmann]

And the cerebellum was described in 1776 in terms of its structures by this fellow called Malacarni. And then some 50 years later, people start to look at what cerebellum does.

[Rachel Gross]

So by the 1800s and early 1900s, scientists are doing these experiments where they basically remove the cerebellum from pigeons and cats or whatever just to see what happens. Okay. But then in World War I, you actually end up with this massive, unintentional human experiment because of the helmets that the British soldiers were wearing. So maybe you've seen pictures of this, but these helmets, they sit up at the top of the head, kind of like an upside down bedpan.

[Latif Nasser]

Yeah.

[Rachel Gross]

And they essentially leave the whole back of the neck exposed, right where the cerebellum is.

[Latif Nasser]

I see.

[Rachel Gross]

And the doctors who were fixing up these soldiers noticed that all of them sort of had the same problem. They would stumble around when they tried to walk. They were really jerky. They would fumble when they tried to reach out and grab for something. In other words, they had difficulty with.

[Jeremy Schmahmann]

The coordination and the timing of the movement.

[Rachel Gross]

So at this point, science basically concludes.

[Jeremy Schmahmann]

Oh, this is all about motor control.

[Rachel Gross]

What the cerebellum is doing is all the stuff in the background that you don't even think about when you're moving around in the world.

[Jeremy Schmahmann]

That's correct.

[Rachel Gross]

And that fits really neatly into the map that we were starting to make of the entire brain, where there's kind of this upstairs part, the cerebrum, which is where, like, poetry and art and math and all the things that make us human are happening. And then you have sort of the downstairs, the basement, where we're just sort of doing basic body stuff, animal stuff, like movements, breathing and heart rate.

[Latif Nasser]

Right.

[Rachel Gross]

And of course, what science is interested in is all of that thinky human stuff to the point that even today, if you look at most neuroscience papers that say that they're exploring the whole brain, they tend to just ignore the cerebellum completely.

[Latif Nasser]

Wow. Really?

[Rachel Gross]

They literally crop it out of their findings. There are MRI machines that don't cover the cerebellum.

[Latif Nasser]

That's crazy.

[Rachel Gross]

Yeah. And that's probably why all the surgeons I was talking to when I had my stroke were telling me not to worry. The cerebellum is really just making you less clumsy. And it's really not going to be a big deal if we take a little bit out.

[Jeremy Schmahmann]

Well, but almost everything that you've told me was the understanding of the doctors that you've spoken to is outmoded, out fashioned, and predominantly incorrect. Where we are now is a complete paradigm shift. There's been a revolution in our thinking about the cerebellum.

[Rachel Gross]

And can we just back up to where that shift started for you personally.

[Jeremy Schmahmann]

As a resident in the neurological unit of Boston City Hospital?

[Rachel Gross]

This was in 1982.

[Jeremy Schmahmann]

I saw a patient with a stroke in the basal ganglia.

[Latif Nasser]

And what's the. Remind me, what's the basal ganglia?

[Jeremy Schmahmann]

Yeah.

[Rachel Gross]

The basal ganglia are these structures that are deep in the brain, and just like the cerebellum, they've been associated with motor control.

[Jeremy Schmahmann]

But this patient wasn't aware of the left side of space.

[Rachel Gross]

He was having problems with his perception.

[Jeremy Schmahmann]

And that's a syndrome that had been exclusively described in people who have damage.

[Rachel Gross]

To the cerebral hemisphere, like the upstairs thinky brain.

[Jeremy Schmahmann]

So my question was, well, if this motor system can produce a cognitive change, what about the big motor system downstairs? What about the cerebellum? So I had to go back into the stacks of Harvard Medical School's countway library.

[Rachel Gross]

So he's there in the dusty stacks and he's pouring through papers for any little footnote or mention of the cerebellum.

[Jeremy Schmahmann]

And. And he found this subterranean kind of hidden description of cerebellar damage in people whose behaviors were a Little off the beaten track, whether it was mental or emotional or cognitive, but it really got hidden in the literature.

[Lulu Miller]

Everybody knew that the cerebellum controlled motor function.

[Rachel Gross]

And one of the people I came across in my reporting was a scientist named, named Henrietta Leiner.

[Lulu Miller]

And that was it.

[Rachel Gross]

Motor function, they're still teaching that. I think this is an interview of her talking about the cerebellum before she died.

[Lulu Miller]

When I first proposed the hypothesis about.

[Rachel Gross]

The cerebellum, she'd been arguing that the cerebellum was actually influencing cognitive functions in the upstairs brain.

[Lulu Miller]

The peer reviewer of the paper turned it down with a this couldn't possibly.

[Rachel Gross]

Be true or we would have thought of it long ago.

[Jeremy Schmahmann]

But, you know, science gets driven by people who have powerful influence. And those folks who were saying this is motor control won the day.

[Rachel Gross]

And you, I guess, did you start to look into that? What was your next step?

[Jeremy Schmahmann]

So we started looking at the anatomy of how the upstairs brain talks to the downstairs brain.

[Rachel Gross]

Jeremy figured that if the cerebellum is doing more than just motor stuff, then there would need to be some sor of like, infrastructure between the two.

[Jeremy Schmahmann]

In other words, does the cerebellum have access to information that is beyond motor control information?

[Rachel Gross]

So Jeremy and his mentor, Dr. Dhiraj Panya, this was in the late 80s. They took rhesus monkeys and injected their cerebrums, or the upstairs brain, with these dyes that act like tracers, tracers that.

[Jeremy Schmahmann]

Get picked up by the nerve cell.

[Rachel Gross]

Then they left up the monkeys for a week or so, just going about their day, thinking monkey thoughts. And meanwhile, these dyes travel down the.

[Jeremy Schmahmann]

Nerve and they end at the point where the nerve ends.

[Rachel Gross]

And what Jeremy ends up seeing is these lit up highways going down to.

[Jeremy Schmahmann]

The cerebellum from areas of the brain relevant for executive control functions. In the frontal lobe, awareness of ourselves in the environment. Parietal lobe, temporal lobe, involved in language processing. In the gyro, emotional modulation. Am I getting too sciency?

[Lulu Miller]

No, we love it.

[Brandon Beltz]

It's called radio lab, you know.

[Jeremy Schmahmann]

So all those areas send information into the cerebellum. And then other investigators showed that the cerebellum sends information back up to the thinking brain. So now, in a word, you have an anatomical circuitry linking cerebellum to the thinking brain.

[Rachel Gross]

Wow.

[Robert Barton]

Yeah. The neocortex and the cerebellum are massively interconnected.

[Rachel Gross]

And according to evolutionary biologist Robert Barton at Durham University in the uk, there.

[Robert Barton]

Seems to be a very particular evolutionary relationship between these two structures.

[Rachel Gross]

These connections between the thinky brain and the motor brain might actually be a big part of the story of how humans became humans.

[Lulu Miller]

Huh.

[Robert Barton]

One of the really popular ideas about brain evolution is predominantly a story of the expansion of the cortex. But we made two discoveries that kind of started to challenge that conventional wisdom.

[Rachel Gross]

So what he and his colleagues did was gather up a bunch of data about the size and the structure of the brains of a bunch of different primates.

[Robert Barton]

And then if you know how those species are related to each other, you can reconstruct patterns of evolutionary change.

[Lulu Miller]

Interesting.

[Rachel Gross]

So the first thing Robert notices is.

[Robert Barton]

That across all of the primates, their.

[Rachel Gross]

Cerebrums and cerebellums are evolving in lockstep.

[Robert Barton]

They're pretty tightly coordinated. But then we stumbled on a pattern in the data that took me by surprise, which was that when we get to the apes, the ape part of the story, we see a deviation from that general pattern of coordinate. What we see in the apes is an acceleration in the expansion of the cerebellum.

[Lulu Miller]

Wait, so you're saying, like, the cortex got bigger, but the cerebellum got big, faster.

[Latif Nasser]

Wow.

[Robert Barton]

Kind of outstripping it.

[Rachel Gross]

So what Robert is really saying here is that right at the moment that we are becoming human, which everyone has assumed was all about the upstairs brain, it was actually the cerebellum. So the lower brain that was rising to the moment.

[Robert Barton]

Yeah, exactly.

[Rachel Gross]

To the point where in the human.

[Robert Barton]

Brain today, although it's a lot smaller than the neocortex, it has about four times more neurons.

[Rachel Gross]

What?

[Alison Hilger]

That's a lot.

[Lulu Miller]

That's bonkers.

[Jeremy Schmahmann]

The cerebellum has about 80% of the brain cells that we have.

[Lulu Miller]

Wait, 80% of the brain cells of our whole brain are in the cerebellum.

[Rachel Gross]

Right.

[Jeremy Schmahmann]

There's a lot of brain in there.

[Latif Nasser]

And that cropped out of the MRIs or whatever.

[Rachel Gross]

Exactly, exactly.

[Jeremy Schmahmann]

But here's the thing that's remarkable. Most of the cerebellum, in terms of the size of cerebellum, is the region that is interconnected with thinking brain, not motor brain.

[Rachel Gross]

Wow.

[Jeremy Schmahmann]

Most of the human cerebellum has nothing to do with motor control.

[Latif Nasser]

So to collect what we have here.

[Rachel Gross]

Yeah.

[Latif Nasser]

There are old case studies where people with cerebellum injuries. It's more than just a motor problem.

[Rachel Gross]

Yeah.

[Latif Nasser]

Ape and human cerebellums are bigger than other primate cerebellums.

[Rachel Gross]

Exactly. Right.

[Lulu Miller]

And it's massively connected to the rest.

[Latif Nasser]

Of the brain to thinky parts.

[Rachel Gross]

Yeah.

[Alison Hilger]

Okay.

[Latif Nasser]

So I still. I still do not understand what is this thing even doing.

[Rachel Gross]

I mean, that's the 80 million neuron question or the 80 billion neuron question.

[Lulu Miller]

And we will get to that right after this break. Hi, I'm Lulu Miller and this episode is sponsored by Better Help. Well, Happy New Year out there. You know what this time of year means. You might be seeing a lot of people making resolutions about how they are going to transform themselves. They are going to have the perfect routine, the perfect discipline and a wicked strong body. But what if we resolve to just be more okay with who we are? Life's short and the you inside you is the only companion you are guaranteed to have for the whole ride. So why not love on that little you inside you, Work on how to give it some breathing room, some care, whatever the you inside you needs help with. I can say that therapy has absolutely helped me come to more peace with me. But finding an affordable, accessible therapist can be hard. BetterHelp is a great place to start. You fill out a short questionnaire and they help match you to someone they think you'll like. BetterHelp says they typically get it right the first time, but if it's not a good fit, switching is very fast and easy. If you want to try it out, you can sign up right now and get 10% off at betterhelp.com radiolab@ that's betterhelp.com Radiolab.

[Latif Nasser]

Radiolab is supported by Planet Visionaries, the podcast created in partnership with the Rolex Perpetual Planet Initiative. The show is hosted by Alex Honnold, who you may recognize from Free Solo, where he climbed El Capitan without ropes. Now he's turning his focus to the biggest challenge of all, protecting the only planet we've got. Previous guests include Mark Ruffalo, conservationist and actor, who discusses how he's leveraged storytelling to galvanize community and upcoming guests include David Gruber, marine biologist and professor known for his research on bioluminescence and innovative underwater imaging techniques. In partnership with the Rolex Perpetual Planet Initiative, this is Planet Visionaries Listen or watch on Apple, Spotify, YouTube, or wherever you're listening to this podcast.

[Ira Flatow]

This is Ira Flato, host of Science Friday. For over 30 years, the science Friday team has been reporting high quality science and technology news, making science fun for curious people by covering everything from the outer reaches of space to the rapidly changing world of AI, to the tiniest microbes in our bodies. Audiences trust our show because they know we're driven by a mission to inform and serve listeners first and foremost with important news. They won't get anywhere Else and our sponsors benefit from that halo effect. For more information on becoming a sponsor, visit sponsorship.wnyc.org.

[Latif Nasser]

Kay Latif Lulu Radiolab.

[Lulu Miller]

We are back talking about the cerebellum, this little part of the brain down near the neck that for a long time was believed to be distinctly about motor stuff. Smoothing walking, smoothing handwriting. Until very recently, scientists began noticing that this part of the downstairs brain was wired up to the big brain upstairs where, you know, all kinds of behaviors like speech and decision making and emotional regulation are processed.

[Rachel Gross]

Right, right. But the question for Jeremy Schmamann at this point is, what is it actually doing?

[Jeremy Schmahmann]

And I remember presenting the anatomy of this story at one of the neuroscience meetings and a well meaning senior colleague said, you're telling us that the cerebellum's involved in behavior. Well, what kinds of behavior? And I really couldn't answer the question. I wasn't sure. So we did what we do in clinical neuroscience. We went to the patient and I met a young woman in her early 20s.

[Rachel Gross]

She had slipped on some ice and fallen backwards and hit her head.

[Jeremy Schmahmann]

It was just a slip and fall, but she had a CAT scan and they found a tumor in the midline of the cerebellum.

[Rachel Gross]

Oh my gosh.

[Jeremy Schmahmann]

The tumor was taken out and she did fine from the motor perspective. But what was noted right from the get go by the nurses in the ward is that she had difficulty coming up with words or using words correctly. She had difficulty with planning and organizing her thoughts. And she'd had a change in her personality.

[Rachel Gross]

Like what kind of change?

[Jeremy Schmahmann]

She was being disinhibited, she was disrobing in the corridor, she was being rude to her parents, she was hiding under the bed covers, she was talking in a high pitched, kind of whiny tone of voice, which was a change for her. But this came from cerebellar damage. The brain upstairs was fine. And we then.

[Rachel Gross]

Since then he's had dozens more patients.

[Jeremy Schmahmann]

Who'D had cerebellar focused damage and they.

[Rachel Gross]

All have different problems with their motor and cognitive and behavioral skills. So what he thinks now is that.

[Jeremy Schmahmann]

Cerebellum is doing, we think for the non motor functions what it's doing for motor control.

[Rachel Gross]

Cerebellum is doing the same thing for our cognitive processes as it's doing for our body.

[Robert Barton]

Yeah, it's using the same kinds of neural circuitry to do those things.

[Latif Nasser]

Wait, but what do they even mean by that?

[Jeremy Schmahmann]

Well, so when you reach out to hold something or to reach something, both.

[Rachel Gross]

Jeremy and Robert Barton Walked me through what the cerebellum does. When you, like, reach out to grab.

[Robert Barton]

Something, think about reaching to grasp a piece of fruit.

[Rachel Gross]

Although Robert wanted to talk about fruit.

[Jeremy Schmahmann]

You'Re reaching out for that cup of coffee.

[Rachel Gross]

And Jeremy was all about the coffee.

[Latif Nasser]

Okay.

[Rachel Gross]

Anyway, with either one, what the cerebellum is doing is figuring out the exact right sequence of moves that you need to make. How to move your arm the right distance, how far it is so you don't like, overshoot or undershoot, how fast.

[Jeremy Schmahmann]

To move your hand, how to time.

[Rachel Gross]

That with the position of your hand.

[Jeremy Schmahmann]

As you reach out to hold the.

[Rachel Gross]

Cup, how much force you're using to gently bring it back to your mouth.

[Jeremy Schmahmann]

Bring it to your lips so you can drink from the cup.

[Rachel Gross]

Or if it's a piece of fruit.

[Robert Barton]

You'Re going to manipulate it in a certain way that will end up with, you know, a nice mouthful of food. Either way, that involves a certain degree of planning of movements and adjustment of your movements as you move your hand in space.

[Rachel Gross]

And that's what the cerebellum is doing. It's like an invisible orchestra conductor doing all the real time, unconscious, behind the scenes adjustments to plan, sequence and time, all the elements of that action.

[Latif Nasser]

I see.

[Robert Barton]

And it's not a huge sort of leap from that to think about the mechanisms that might be involved, for example, in organizing any kind of sequence, including a sequence of vocal utterances. Anything from speaking to produce a well articulated sentence to forming a coherent theme.

[Jeremy Schmahmann]

Absolutely.

[Rachel Gross]

Those things also require the same organizing and planning and sequencing and timing. So the argument here is that the cerebellum is also the invisible conductor of your thinking.

[Jeremy Schmahmann]

It's doing in the same way that kind of information processing to language processing and mental manipulation of information.

[Rachel Gross]

So you're talking to someone at a party, you're telling them about your day, and like you're kind of deciding, like, what parts to leave out, what parts to highlight, what to emphasize, and you're not really even thinking about it. It's all coming out of you. You're kind of hopping from idea to idea and it's just flowing. Yeah, that's the cerebellum.

[Latif Nasser]

Yeah. No, that does sound quite important. That sounds, you know, relatively essential.

[Rachel Gross]

Yeah. And on top of that, researchers are starting to suspect it's doing the same thing for the way we respond emotionally in our lives.

[Jeremy Schmahmann]

Think about your engagement in society.

[Latif Nasser]

Meaning what? Like, somehow affects how you relate to other people?

[Rachel Gross]

I mean, it's like you're kind of understanding how I'm Reacting or what I'm looking for. And you are responding with the right level of emotion. And you're also making little adjustments along the way. You're kind of like putting something out into the world and you're getting a reaction back and then you're deciding, okay, maybe I went too far with that. Maybe I should like tone it down a little. It's reading whatever room you're in and helping you attune yourself to it. And that's why, in addition to having trouble with organizing thoughts and using language, Jeremy's patient had these behavioral issues.

[Jeremy Schmahmann]

She could be withdrawn and flat affect, disinhibited and inappropriate in comments. And so there's an overshoot and undershoot in emotion regulation.

[Lulu Miller]

Had you experienced that side of it?

[Rachel Gross]

Yeah. Specifically with emotion, I have found myself even in the past few months, like laughing extra loud at something or like the reaction came out different than I expected.

[Lulu Miller]

Like a little bit bigger. A little bit. Yeah, yeah.

[Rachel Gross]

And one thing that happens a lot is I have a block where a word escapes me. So it's more nerve wracking to have like spontaneous conversation.

[Latif Nasser]

Right.

[Rachel Gross]

And now it's like I'm kind of pulling each lever and I have to be more aware of exactly what words I'm using, how I'm showing emotion. I have to manually do all these things that used to be unconscious and in the background.

[Latif Nasser]

It is kind of stunning how many different things, things this one little part of the brain is doing.

[Rachel Gross]

Yeah, it's really crazy to think that for the first couple hundred years of brain science, up until I was speaking with my surgeons about having some of mine removed, we considered this part of the brain just a motor control device.

[Robert Barton]

In the west in particular, we have thought about thinking for hundreds of years as distinct from movement. It started with dualism and Descartes and the way that Western culture conceives of, you know, the soul as something other than and apart from the body. But that's the wrong way to think about thinking. Thinking is intrinsically related to the way we move around in the world. There's no point at which, you know, in evolution we can sort of validly recognize some kind of magical transition from one to the other. They're continuous with each other.

[Rachel Gross]

For Robert and for Jeremy too, the cerebellum represents this crucial link between movement and thinking. And they think that if you want to understand how our brains do all the things they do, like navigate language and math and logic and emotion and art in this natural and fluid way, the cerebellum is the place to look.

[Robert Barton]

I mean, I think of the cerebellum as the Cinderella of brain structures. You know, it's kind of shyly concealed beneath the cortex, ignored and its qualities underappreciated. Well, it's time Cerebella came to the ball.

[Latif Nasser]

You're telling us all this, like, very helpful science, but, like, taking the reporter hat off. Like, how do you. How does. How does that feel, that to be learning all this stuff, knowing that it is. Yeah. Like, it's clearly so personal.

[Rachel Gross]

Right. Well, I think initially it felt like I was starting to understand what's happening inside me, and it's helping explain why I feel this persistent sense that there's something off, and that's kind of, like, helpful and satisfying. But then it's also bittersweet because it's kind of forcing me to dwell on what I have lost, which is this effortless, like, fluidity that I didn't even realize I had. And as a writer who puts a lot of stock in selecting the right image and idea and word, I can't help but sometimes feel inadequate. And so it's. I'm. I'm endlessly fascinated by the body, but every time it does come back to me and I'm put back in the patient role, suddenly that curiosity kind of, like, disappears, and I, like. I don't know that I want to know anymore about everything that I've. So I kind of turn towards the science of recovery and how much we still don't know about how the brain heals and adapts after injury. We're good to go.

[Robert Barton]

Great.

[Rachel Gross]

Wonderful. Would you mind. And that led me to a neuroscientist named David Eagleman.

[Latif Nasser]

Amazing. We love Eagleman.

[David Eagleman]

I mean, I have to say, I'm not a cerebellum expert as such, so if somebody says, look, there's a new part of the cerebellum, I'd be interested, because I didn't know about that.

[Rachel Gross]

He wasn't really, like, up on the latest research about the cerebellum, but what he'd really studied a lot was how the brain recovers after injury or damage.

[David Eagleman]

Yeah, the whole system is so flexible.

[Rachel Gross]

And he'd found that the key to tapping into that flexibility was motivation.

[David Eagleman]

Everything is about the motivation for it. If I tried to run a rehab program for you, and I said, look, Rachel, we're going to teach you how to play the tuba. And you said, I really don't care about the tuba. And I'm like, no, this is great. You're gonna play the tuba. You're just not gonna get very far because you need the right cocktail of neurotransmitters there for plasticity to happen, and that generally maps onto motivation.

[Rachel Gross]

I truly have no interest in the tuba. It's Saturday, August 3rd. But what I realized was I'm already doing this with karaoke. I don't want anybody else. And after talking to David, I kind of just threw myself even deeper into that. That felt pretty off, but maybe I can relearn it. I practiced at home. I recorded myself. I took voice lessons. Just a little wobbly, wobbly. Let's try again. All right, Take two. Let's try this one more time. Take three. I felt like if I could just get my karaoke back, I would be back. Okay, well, that happened, and I'm not going to panic, but obviously it's not as natural anymore. Used to be one I knew pretty much by heart, so I better practice. It was kind of like bashing my head against a wall. Like, no matter how many times I sang the song, something still felt.

[Alison Hilger]

Yeah, right there at the beginning. I heard you go up and then down. It was like you're trying to calibrate to the note up and down.

[Rachel Gross]

So I actually ended up calling this speech language pathologist named Alison Hilger.

[Alison Hilger]

Singing is actually the most complicated, most coordinated movement you will ever do in your body.

[Rachel Gross]

And she told me that the cerebellum is involved in almost every part of singing.

[Alison Hilger]

Oh, my gosh. So you take a breath. Your lung volume has to be at a certain level. Not too high, not too low. If it's too high, you have too much pressure below your vocal folds, and maybe you'll talk too loudly. If it's too low, you're kind of, like, gravelly, and it's hard to talk. Your vocal folds then have to come together at a specific time. There have to be a certain tension.

[Rachel Gross]

Again, the cerebellum is the invisible conductor of all of these fine muscle movements.

[Latif Nasser]

Right.

[Rachel Gross]

But the thing I didn't realize until I did this reporting is that it's also the invisible conductor in all of these other realms. So, like, think about just being on stage and giving a karaoke performance. So you're like. You're reading the lines of the song on a screen. You're kind of conveying the emotion of the song by doing your little hand gestures and dancing and making facial expressions. And then you're also reacting to the crowd in front of you. So you're kind of getting their energy and how they're reacting, and. And you're adjusting your performance in real time to kind of match it. Gosh.

[Lulu Miller]

And that's. The cerebellum is. Boop, boop, boop, boop, boop, boop. It's right at that spot.

[Rachel Gross]

Yeah. Yeah. It's right at that interface. Like, right in that kind of back and forth that, like, dance that you're doing with the world around you. And I feel, looking back, that it was in that fluidity and that ease that I felt in those moments that my sense of self was emerging.

[Lulu Miller]

Yeah.

[Rachel Gross]

And then now that fluidity has kind of broken down, and it's really painful sometimes because I want to tell someone in my life how much I appreciate them or this moment we just shared together and what it meant to me, and the words just don't come out right. And it feels very isolating, like, I just have to hope and, like, take the leap of faith that I said it good enough, that it came out close enough.

[Lulu Miller]

But there's you inside, Judge feeling like, I don't think I did.

[Rachel Gross]

Yeah. Yeah. I think it's helpful when I can figure it out later and then, like, restate it when I have that chance. But, like, a lot of life does happen in these moments that you don't get back.

[Latif Nasser]

Hmm.

[Rachel Gross]

What.

[Lulu Miller]

What do you want to figure out now? Do you have questions that still remain?

[Rachel Gross]

Yeah, I think I want to know, like, is the self a language that I can relearn? And just, like, I kept forcing myself to go back on that stage and try to learn to sing again and try to feel comfortable in a new way. If I keep pushing through that awkwardness and those moments of losing control, all these glitches and mistakes and kind of backtracking, will that ever feel like me?

[Lulu Miller]

So good to see you.

[Rachel Gross]

I'm in a choir for stroke survivors now.

[Jeremy Schmahmann]

Really?

[Rachel Gross]

Yeah, me. And, like, when did that happen? A few months ago. There's, like, a TBI support group that I'm in. They sent a link for this choir called Measure by Measure, and I was like, yeah, this is perfect, because it's like a support group, but everyone's connected by something that gives them joy.

[Lulu Miller]

Yeah.

[Rachel Gross]

Tuesday morning. And, like, I'm the only person under 70, and I clearly, like, recovered a lot more than most people in the choir, many of whom were musicians in the past, To be able to still sing after that, in whatever way you can. And know what would have come easier to you? Yeah. To just hold, like, the fact that there is that kind of deep loss in life. You do have to let go of some of that. Let go of, like, control and this image of what you should be and how it should be coming out and just, like, live fully in the moment that you have now. What did he say? It's like people trying to be in community and be on the same page and feel the same song together in whatever, like, stumbling way we can. Nice to see you back.

[Lulu Miller]

Take in the miracles around you every day. Have a great week.

[Jeremy Schmahmann]

Thank you.

[Rachel Gross]

So there actually is one more thing that I have to tell you guys.

[Latif Nasser]

What is it?

[Rachel Gross]

When Cindy was recording me at Branded that one night, um, next day, I got a DM on Instagram from someone who was there, who found me by my first name and the fact that I followed the karaoke bar. Wait, wait, can someone just read it? Is that fine to me? Do you want me to read it?

[Lulu Miller]

Okay.

[Latif Nasser]

Wait, what?

[Jeremy Schmahmann]

Hi.

[Rachel Gross]

This is certainly awkward, but I noticed you at karaoke last night. In parentheses. Look, there are only so many Rachels who follow Brandon on Instagram, and here we are. Well, anyway, I think maybe there was a connection. And I'm still hitting myself for not coming to talk to you then. So now I'm shooting my shot. Can I buy you a cup of coffee again? Can we read? Rachel, your response? Bold move, hitting on a girl with short hair at a gay bar. Fortunately for you, I felt the same smiley face. Thanks for doing the heavy lifting finding me on Insta. I'm impressed enough to definitely let you buy me a drink. P.S. you had some rizz up on that stage.

[Lulu Miller]

What?

[Rachel Gross]

So damn grateful you're doing the story.

[Latif Nasser]

Wait.

[Lulu Miller]

Stop it. So, wait, so, like, your singing voice, your new cerebellum. Inflected cerebellum injury. Inflected singing voice. Literally, like, hooked you a lover? What song? Or, like, I mean, we have a recording of this?

[Rachel Gross]

Yeah. So it was. Objection. Tango. The Shakira song. Life is funny, you guys.

[Lulu Miller]

Life is fun.

[Brandon Beltz]

Get away.

[Rachel Gross]

Oh, are you falling apart in your hands again? Go ahead. I am falling apart in your hands again.

[Lulu Miller]

Awesome.

[Latif Nasser]

Thank you, rachel.

[Robert Barton]

Thank you.

[Latif Nasser]

Thank you, rachel.

[Lulu Miller]

The one, the only, Rachel Gross on the mic. This episode was reported by Rachel Gross and produced by Sindhu Namasambandan. Fact checking by Angeli Mercado Special thanks.

[Latif Nasser]

To Thursday Karaoke warzone at Branded Saloon. Dag Spicer, curator of the Computer History Museum, and Joanne Lowy, the director of the Singing Together Measure by Measure choir for stroke survivors at the Louis Armstrong Department of Music Therapy.

[Lulu Miller]

Thanks also to Daniel A. Gross, Desiree Lee, Mark Gross, Brittany Aguilar, the 14 rhesus monkeys that helped us learn about the links between the upstairs and downstairs brain. And Rachel wanted us to pass on a sincere note of gratitude to Shakira.

[Latif Nasser]

Who, in fact checking, we learned that her hips do not lie. It's true. If you want to learn about another overlooked part of your brain, check out our episode, damn it, Basal ganglia. It also involves someone getting pulled more intimately into the mystery of their own brain than they realized they would.

[Lulu Miller]

That's it for today. Thank you so much for listening.

[Latif Nasser]

Catch you next week.

[Brandon Beltz]

Hi, I'm brandon beltz and I'm from new paltz, new york, and here are the staff credits. Radiolab is hosted by lulu miller and lateef nasser. Soren wheeler is our executive editor. Sarah sandbach is our executive director. Our managing editor is pat walters. Dylan keefe is our director of sound design. Our staff includes jeremy bloom, w. Harry fortuna, david gable, maria paz, gutierrez, sindhu nyan sumbundun, matt kielti, mona madgaalker, annie mcewen, saru khari, rebecca rand, anissa vitza, arian wack, molly webster, and jessica yong. Our fact checkers are diane kelly, emily krieger, natalie middleton, angeli mercado, and sophie samii.

[Rachel Gross]

Hi, I'm monica and I'm coming from mexico city. Leadership support for radiolab science programming is provided by the simons foundation and the john templeton foundation. Foundational support for radiolab was provided by the alfred p. Sloan foundation.

[David Eagleman]

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[WNYC Sponsor Announcer]

Since WNYC's first broadcast in 1924, we've been dedicated to creating the kind of content we know the world needs. In addition to this award winning reporting, your sponsorship also supports inspiring storytelling and extraordinary music that is free and accessible to all. To get in touch and find out more, visit sponsorship wnyc. Org.