Featured Image: These fMRI images from Jean Gotman at McGill highlight a small part of the brain, because it’s statistically more active than it was at some other moment. Remember: the other 90% of the brain is still actively in use!
For this week’s show, we replayed an earlier interview from Sam McDougle, a graduate student in the Department of Neuroscience at Princeton. He and Stevie dive into his research on motor skills, learning, and the brain, and they debunk the ever-popular myth that we only use 10% of our neurons at once. After the interview, I describe the Earth’s dynamo problem and some new research from Osaka University that raises more puzzles than it solves.
Sam and the rest of the Taylor Lab want to know what the brain is doing when we learn new skills. We’re all used to the feeling when something clicks and a skill becomes easy for us: riding a bike, cutting with scissors, and typing have all become automatic for us eventually. But initially, developing a new task into a skill requires practice. Building up muscle memory and neuronal networks that fit the task is a long process in the brain, and it’s hard for science to unveil completely. As Sam says, researchers rarely find conclusions, they just scramble for hints until they can piece together ideas about the truth.
To study the learning process, Sam first experimented on mice, fitting them with brain electrodes and having them repeat behaviors. But even though the brain fundamentals are very similar between mice and humans, the complicated tasks that people have to learn go beyond the range of mouse-science. Now, Sam brings in human volunteers to study instead, and relies on less invasive data collection (like fMRI instead of electrodes inside the skull).
To be clear, there’s a lot going on in the brain at once. An fMRI scan may just show a small blob of color somewhere in the brain, but this highlight just shows a place where the brain was more active than it used to be before the experiment. Sam’s brain scans might showcase, for example, neural areas that handle muscle memory; but even as these particular brain sections are especially active, the rest of the neurons are still abuzz. The myth that “we only use 10% of our brains” might have originated in Dale Carnegie’s famous self-help book, How to Win Friends and Influence People–and even there, it only appears as a misattributed quote in the foreword. So don’t believe the rumors, because your whole brain is always hard at work.
Testing hypotheses on human subjects is no easy matter. For one, Sam can’t have people learn nuanced skills in the experiment. To teach thirty subjects to play the violin and measure their brainwaves as they do it will take months, will cost a lot, and won’t be very repeatable from person to person. Instead, Sam and his colleagues have to think of tasks that are complicated enough that we must learn them, but are still so simple that the study can proceed quickly and repeatably.
One result of the studies so far is the demonstration of “implicit” versus “explicit” motor skill learning. Teaching someone to snowboard might involve phrases like “keep your weight on your back leg” or “dig in to brake;” these “explicit” instructions give the learner some reference for improving quickly. But, verbal commands alone can’t do the whole job, since most of the learning comes from testing behaviors out. Imagine reading a book about swimming and then jumping in the pool for the first time: you’d still have a lot to figure out about treading water. The implicit skills you develop from trying, failing, and trying again are ultimately the backbone of mastering a task. Sam’s results show that implicit and explicit learning are stored in different parts of the brain, and the research is still attempting to find connections between the two.
Sam closed the interview with a bit about his own musicianship. Among many projects, he plays and records his own music as Polly Hi. I anachronistically played a song from Deceleration, Sam’s newest album, which actually came out months after this interview last year.
I ended the show with a major problem in astrophysics and geology: why is the Earth still magnetized? From what we know about currents and electricity, magnetic fields should decay over time and eventually die out. However, the Earth has a strong magnetic field: it keeps us safe from the solar wind, helps maintain our atmosphere, and brings the auroras to the poles. So, something doesn’t add up. The Earth’s core must have some net current or flow that maintains the magnetic field over billions of years.
Scientists at Osaka University just did an experiment to simulate the Earth’s core and resolve this issue once and for all. The core is made of nickel and iron, so the group put iron wires into a diamond anvil–a device that generates gigantic pressures on a tiny area in a lab. By heating the wires with lasers and putting a current through them, the scientists measured how well iron can conduct a current in the middle of the Earth. Based on their measurements and how strong the Earth’s magnetic field is, the Earth should be about 700 million years old. The problem: it’s much, much older than that (over 4 billion years!).
What does this puzzling result tell us? Largely, it’s that there are properties of the Earth’s core that we don’t understand at all. You might think that by being space explorers and mastering fracking and plate tectonics, we’d have figured out the composition of the Earth by now. Unfortunately, while we do understand the crust and mantle of our planet, the nickel-iron core is inaccessible to direct measurement. We can study waves that pass through the middle of the Earth, and we can study high-temperature high-pressure materials in the lab, but understanding the complex motions at the middle of the Earth is probably a long way away.
As always, the playlist is on WPRB or below.