Issue 83

Brainwaves, sound objects, and dubiously-dubbed safe ingredients

Oct. 26, 2019

Hello friend! Welcome to Scrap Facts.

I'm a reporter covering health and science with insatiable curiosity. I love everything I learn, not all of which gets its own story. Each week, I'll bring you some of my favorite facts that I picked up on the job or while out living life.

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Your brain makes waves for all occasions—and they can be therapeutic, too.

Found while reporting: The future of Alzheimer’s treatment can’t bank on just one drug.

The big story in the news this week was that for the first time in over a decade, an Alzheimer’s drug passed a last-stage clinical trial. This means that it could hit the market as early as 2020, when Biogen, its manufacturer, files for approval from the US Food and Drug Administration.

I have a lot of thoughts about why this news should revitalize other avenues of Alzheimer’s research, too. You can read them in this Twitter thread. Or you can read the article above! But I’m not gonna recap it here—instead, I’m gonna talk about brainwaves.

This week at the Society of Neuroscience—a very prestigious meeting of the minds (heh) for top researchers in the field—a researcher from the Massachusetts Institute of Technology named Li-Huei Tsai spoke about a new potential therapy for Alzheimer’s: Flashing lights and a clicking noise played 40 times per second for an hour at a time.

If you’re not familiar with the work (which I wasn’t as of a few weeks ago), it sounds like pseudoscience. But it turns out, promising mouse studies have shown that when light and sound hit a certain frequency—roughly around 40Hz—groups of neurons in the brain start emitting electrical charges at the same frequency. And somehow, these oscillating electrical frequencies, aka brainwaves, change the neuron’s collective behavior. They can call in other kinds of brain cells, like microglia, which work like the brain’s housekeepers to clean out clumps of amyloid and other gunk.

This brainwave frequency is called a gamma rhythm. These same oscillations happen when we’re engaged in mentally stimulating tasks (like reading this newsletter) or going through rapid-eye movement in sleep.

We have other brain waves, too: Delta waves, the slowest, occur in deep sleep. Theta waves happen when we’re barely awake, alpha waves happen when we’re awake but closing our eyes, and beta waves happen when we’re awake, but relaxing. In other words, the faster the brain waves, the more brain power we’re using. This Nature article breaks this all down in a pretty graphic.

Not all of our neurons oscillate at the same rhythm at any given time, but usually a majority of neurons set the brain’s overall tone. What’s the purpose of them? Scientists aren’t sure (some researchers don’t think they matter at all). Why do some neurons sync up with each other? Also unclear. How is it that neurons pick up on frequencies happening from external sources like light or sound? You guessed it—it’s still a puzzle scientists are figuring out.

Either way, it seems to work therapeutically, and there’s minimal risk of side effects. In addition to more research happening at MIT, Tsai co-founded a company called Cognito that is currently administering early clinical trials for different types of gamma rhythm therapy in people with early stage Alzheimer’s. I spoke to the president of the company, who was hesitant to give me too many details about the trial for fear that if I described it in detail, those getting the placebo may realize they’re not getting the treatment. They should be wrapping up no later than January 2020.

Our brain recognizes some sounds as “objects.”

Found while reporting: A new look at how the brain processes sound could radically improve hearing aids.

Say, friend, that you and I decided to go out to a crowded bar on a Friday night with our good friend Bill Nye. If Nye and I got into an argument about which animal has the wildest capabilities and started talking over one another, you’d be able to pick out one of us to listen to. It’s a process that happens nearly instantaneously* and automatically. But it’s actually an incredibly complex process.

In this hypothetical scenario, as I scream, “The aye-aye is the only primate to have six fingers, one of which is on a ball-and-socket joint!” over Nye’s babbling about gastropods, your brain does a neat editing trick: First, it picks out both of our words as speech, and lays them out one over the other, like audio editing software lining up two tracks. Then, it dials down Nye’s voice and turns the volume up on mine, much like producers cut English translations over a foreign speaker’s voice on a radio show.

The brain can do this, in part, because it turns out it comprehends some distinct sounds the way our eyes see objects—and knows what they are when we don’t see a complete picture. For example, we know that tables have four legs and a flat top. If you saw a table from an angle where you could only see three legs, you’d still know it was a table, and your brain could fill in the rest.

Same goes with important sounds like speech: Even if you can’t hear all of the words being said—Nye is really trying to shout over me—your brain can do a pretty good job at filling in the blanks with what it expects to hear. In this case, words in English about the miracle of ball-and-socket joints.

(Cool, right? I wrote this same fact as a comment to the story on the Quartz app—check it out here.)

From a technological standpoint, this work could make better hearing aids, which aren’t good at picking out one person’s speech over another. But from a broader research standpoint, learning more about the way the brain interprets sound could make hearing one of those rare sensory windows into the brain.

*Bonus fact: The amount of time needed for your auditory cortex to tune into a single voice? 150 milliseconds.

The US Food and Drug Administration hasn’t updated the compounds that are “generally regarded as safe” in decades.

Found while reporting: What’s actually in an e-cigarette?

One of the main reasons so many people thought e-cigarettes were safe were that the ingredients are nothing new. In fact, the ingredients in legally sold e-juice are all “generally regarded as safe”—a designation created by the FDA.

There are hundreds of GRAS chemicals. The regulatory agency created the designation in 1958, when it started regulating food additives. Rather than requiring previously used food additives to go through extensive (my read: expensive) testing, the FDA decided to grandfather in these additives as “regulated” because they didn’t seem to be harming people yet, and they likely wouldn’t.

Vegetable glycerin and propylene glycol, a combination of which carry nicotine and flavorings in most e-cigarettes, are both GRAS chemicals. This means that “there is no evidence in the available information on [substance] that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current or might reasonably be expected in the future.”

However, the last time the FDA reviewed data these chemicals was in 1975 and 1973, respectively. And they were specifically reviewed for their use in food, and later cosmetics and drugs. They’ve never been reviewed for safety when inhaled as aerosols heated by a metal wick—which is essentially what vaping does. And taking stuff in through the lungs is way different than taking it in through other routes of the body. Robert Tarran, a biologist at the University of North Carolina, gave me water as an example: just because it’s safe—and even good!—to drink it, getting water in your lungs can be fatal.

Bonus fact: An ode to lungs

Reporting this story, read a wonderful review of all the research on e-cigarettes’ safety, and I was tickled by the introduction. It’s endearing to see such enthusiasm for our anatomy, which is something I, too, feel on a regular basis.

The lungs are a physiologic marvel, transmitting the entire cardiac output through around 2,000 km of capillaries with each heartbeat and performing gas exchange in 300,000,000 alveoli with a surface area of about 70 m. With every breath, this highly adapted and delicate organ is exposed to infectious and inflammatory environmental stimuli. As a result of innate and acquired immunity, inspired air is cleaned and humidified before it reaches the alveoli. 

Animal of the issue: Tasmanian tigers

In honor of Halloween approaching, I present to you an animal that seems to back from the dead (er—extinction).

The Tasmanian tiger, or thylacine, was—is?—the largest meat-eating marsupial (mammal with a pouch) living on Australia’s southern-most island. It’s been extinct since the 1930s, but there have been a lot of sightings reported around the island—especially over the past couple of years. So maybe it’s not?

This New Yorker piece does a great job of showing how those determined to find thylacine almost sound like Bigfoot enthusiasts—which would make it extra strange if the animals turn out to be alive.

Stuff I learned from others:

We can track where Lewis and Clark traveled in the US thanks to their toxic laxatives. You will never guess the most vegan-friendly city. Good luck getting pure Scotch whiskey in the US any more. A rare minority of people have guts that can ferment alcohol when they eat carbs. White bellbirds are not subtle flirts. Every piece of coal found is chemically unique. Butterflies are moths who got tired of working the night shift.

One programming note: Friend, I am going to be missing from your inbox for the month of November. I’m working on a project I’m excited to share with you in December. Sit tight, and stay curious until then!

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Top image by E. Y. Smith, headshot drawing by Richard Howard.

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