Linguistic brain atlas

Well, folks, I'm going to be away for a little while again... and I'll be out of wifi and cellphone range (for those of you who know my general attitude about technology, you can probably imagine what a respite this will be for me).  I'll be back with a new post on Monday, August 15.  See you in a few days!

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Science is amazing.

I know, I know, I say that every other day.  But there are times when I read the science news and am completely overwhelmed by how cool it all is, and am frankly astonished by our ability to parse the way the universe works.

The most recent research that provoked that reaction is a paper that appeared in Nature this week entitled, "Natural Speech Reveals the Semantic Maps that Tile Human Cerebral Cortex," by Alexander G. Huth, Wendy A. de Heer, Thomas L. Griffiths, Frédéric E. Theunissen, and Jack L. Gallant.  And what this research has done is something I honestly didn't think was possible -- to create a "brain atlas" that maps how words are organized in the cerebrum.

[image courtesy of the Wikimedia Commons]

The scientists did this by having subjects in an fMRI machine listen to the MOTH Radio Hour, a compelling storytelling program that the researchers thought would be riveting enough to keep people's interest and their minds from wandering.  And while they were listening, the fMRI mapped out which words and groups of words triggered responses in tens of thousands of spots all over the cerebral cortex.

"Our goal was to build a giant atlas that shows how one specific aspect of language is represented in the brain, in this case semantics, or the meanings of words," said study author Gallant, a neuroscientist at the University of California, Berkeley.  As science writer Ian Sample of The Guardian put it:

The atlas shows how words and related terms exercise the same regions of the brain. For example, on the left-hand side of the brain, above the ear, is one of the tiny regions that represents the word "victim."  The same region responds to "killed," "convicted"," "murdered" and "confessed."  On the brain’s right-hand side, near the top of the head, is one of the brain spots activated by family terms: "wife," "husband," "children," "parents."

Further, as many words have more than one definition, the researchers were able to map how context influences meaning and changes the site of brain activation.  The word "top," for example, can mean a child's toy, a woman's shirt, or can be a relational word that describes position.

The study's authors write:

We show that the semantic system is organized into intricate patterns that seem to be consistent across individuals.  We then use a novel generative model to create a detailed semantic atlas.  Our results suggest that most areas within the semantic system represent information about specific semantic domains, or groups of related concepts, and our atlas shows which domains are represented in each area.  This study demonstrates that data-driven methods—commonplace in studies of human neuroanatomy and functional connectivity—provide a powerful and efficient means for mapping functional representations in the brain.

The research is groundbreaking.  Lorraine Tyler, cognitive neuroscientist and head of the Centre for Speech, Language and the Brain at Cambridge University, described it as "a tour de force" -- a phrase scientists don't use lightly.  There is already talk of using the research to allow people who are unable to speak for reasons of illness or injury, but whose other cognitive processes are undamaged, to communicate with speech-production software via a brain/computer interface.  What other applications might come up are mind-bending even to consider.  Uri Hasson, a neuroscientist at Princeton, said, "There are so many implications... we are barely touching the surface."

So once again, it's science for the win.  It's heartening to think, in this age where I'm often afraid to open up the newspaper for fear of finding out what new and unusual ways we've come up with to be horrible to one another, that we are capable of elegant and beautiful research that elucidates how our own minds work.  As Carl Sagan put it, "We are a way for the cosmos to know itself."

The paper's authors write:


We show that the semantic system is
organized into intricate patterns that seem to be consistent across individuals. We then use a novel generative model to
create a detailed semantic atlas. Our results suggest that most areas within the semantic system represent information
about specific semantic domains, or groups of related concepts, and our atlas shows which domains are represented in
each area. This study demonstrates that data-driven methods—commonplace in studies of human neuroanatomy and
functional connectivity—provide a powerful and efficient means for mapping functional representations in the brain.



We show that the semantic system is

organized into intricate patterns that seem to be consistent across individuals. We then use a novel generative model to

create a detailed semantic atlas. Our results suggest that most areas within the semantic system represent information

about specific semantic domains, or groups of related concepts, and our atlas shows which domains are represented in

each area. This study demonstrates that data-driven methods—commonplace in studies of human neuroanatomy and

functional connectivity—provide a powerful and efficient means for mapping functional representations in the brain.

We show that the semantic system is

organized into intricate patterns that seem to be consistent across individuals. We then use a novel generative model to

create a detailed semantic atlas. Our results suggest that most areas within the semantic system represent information

about specific semantic domains, or groups of related concepts, and our atlas shows which domains are represented in

each area. This study demonstrates that data-driven methods—commonplace in studies of human neuroanatomy and

functional connectivity—provide a powerful and efficient means for mapping functional representations in the brain.

Enter the Sandman

I've been fascinated with sleep ever since I can remember, and that's mostly because I've been a terrible sleeper ever since I can remember.  I'm one of those people who drifts off thirty seconds after my head hits the pillow, then wakes up at two AM with my mind spinning and can't get back to sleep for three hours.  All well and good on summer break, when I can take an afternoon nap if I need to, but it plays hell with my alertness and general mood during the school year.

Things have gotten a little better since I got a CPAP machine last year -- turns out I have obstructive sleep apnea due to a "narrow tracheal opening" (I have none of the other risk factors).  It was serious, too.  When I got the results of my sleep study, I was told that I was waking up an average of 23 times an hour.  Yes, that means that in an average eight-hour night, I was waking up over 180 times.

No wonder I was perpetually exhausted.

Since getting on a machine to regulate my breathing, it's gotten better, but I still am prone to wee-hours wakefulness and being tired in the middle of the day.  Annoying, but a malady I share with a lot of people, apparently.  And I've always wondered, what's sleep for, anyway?  What can possibly be so important that we slumber away on the order of a third of our life?

[image courtesy of photographer Evgeniy Isaev and the Wikimedia Commons]

The answer is: we don't know.  Evidently it's something not unique to humans -- virtually every animal species studied sleeps, and the more complex the brain, the more sleep they need.  There are hypotheses that sleep helps to reset the sensitivity of neurotransmitter receptors, that it allows consolidation of memories, that it facilitates the removal of toxic waste products from brain cells.  All are, at the moment, unproven.

All that's known is that when people are deprived of sleep for long enough, they kind of go off their rockers.

So it was with great interest that I read a paper last week in Nature called "Operation of a Homeostatic Sleep Switch" by Gero Miesenböck of Oxford University et al.  The research team studied sleep mechanisms in fruit flies:

Sleep disconnects animals from the external world, at considerablerisks and costs that must be offset by a vital benefit.  Insight into this mysterious benefit will come from understanding sleep homeostasis: to monitor sleep need, an internal bookkeeper must track physiological changes that are linked to the core function of sleep.

Miesenböck was interviewed by Sarah Kaplan of The Washington Post and described how an experiment on fruit flies could elucidate mechanisms of sleep in other animals:

Think about it.  We do it.  Every animal with a brain does it.  But obviously it has considerable risks...  If evolution had managed to invent an animal that doesn’t need to sleep... the selective advantage for it would be immense.  The fact that no such animal exists indicates that sleep is really vital, but we don't know why.

In order to study this response, Miesenböck's team used fruit flies that were genetically engineered for specific proteins to be switched on and off by laser light.  In particular, these flies had an artificial switch in their dorsal fan-shaped body (dFB), a cluster of cells that is known to be correlated with sleep.

They used the laser switch to release dopamine into the dFB, which suppresses activity in those cells, causing sleeping flies to immediately wake up.

In particular, there was one gated-channel protein that was off when the flies were sleeping and on when the flies were awake.  If the scientists turn the channel off permanently...

... the flies go into an unending sleep state.

It's like the stuff of fairy tales, except that there's no Prince Charming of the Fruit Flies.

The channel has been nicknamed "Sandman," for obvious reasons.  "It's beautiful, the self-correcting logic of the feedback mechanism," Miesenböck said.  "It's one of those things that gives you goose bumps when you see how it actually works because it's so, so unexpectedly simple and elegant."

An open question is whether the flies that can't wake up will live longer, since sleeping less is correlated with a shortened life span (both in fruit flies and in humans).  Miesenböck wasn't too fond of the idea of lengthened lifespan at the cost of never being awake, however.  "I don’t know if I would like to live longer if I am asleep most of the time," he said.  "I don’t know what the difference would be from being dead.  Anyway, it's getting philosophical now."

This research, however intriguing, is only the first step.  Whether humans have an analogous system is unknown -- as brain complexity increases, you might expect that the control systems would increase in complexity as well, but that's only a guess.  A complex switching system would likely engender more ways that it can fail.

After all, we don't see many insomniac fruit flies.

On the other hand, I'd love one of those laser-operated reversible sleep switches.  Switch on sleep at 10 PM, and have the "on" switch hooked up to my alarm clock.  Certainly preferable to tossing and turning for hours, although I do have to wonder what I'd do if the power went out in the middle of the night.

Oversleep, is my guess.

this mysterious benefit will come from understanding sleep

homeostasis: to monitor sleep need, an internal bookkeeper must

track physiological changes that are linked to the core function

of sleep

1

risks and costs that must be offset by a vital benefit. Insight into

this mysterious benefit will come from understanding sleep

homeostasis: to monitor sleep need, an internal bookkeeper must

track physiological changes that are linked to the core function

of sleep

1

Sleep disconnects animals from the external world, at considerable

risks and costs that must be offset by a vital benefit. Insight into

this mysterious benefit will come from understanding sleep

homeostasis: to monitor sleep need, an internal bookkeeper must

track physiological changes that are linked to the core function

of sleep

1

Bring on the documentaries

I was in my junior year of college when Carl Sagan's Cosmos first aired.  I, and several of my friends, were absolutely riveted.  After each episode we'd eagerly discuss what we'd learned, what amazing stuff about the universe Dr. Sagan had expounded upon.  I was blown away both by the visual artistry (although it looks antiquated today, back in 1980 it was seriously impressive), and by the music, which was and is absolutely stunning.

[image courtesy of the Wikimedia Commons]

I also remember, however, the backlash Sagan himself received from other scientists.  He was derided as a "popularizer," scorned as someone who presented pretty pictures and watered down, common-language analogies rather than actual hard science.

I thought this was pretty mean-spirited, but I didn't realize how common that perception was in the scientific world.  Four years later, as a graduate student in oceanography at the University of Washington, I found out that there was really only one pair of words that was considered so vulgar that no one was allowed to utter it: "Jacques Cousteau."  Cousteau was an object of derision, not a "real scientist" at all, just a guy who spoke in a cheesy French accent and liked to get filmed while scuba diving.  In fact, my adviser once told me that he made a point of never accepting a graduate student who mentioned Cousteau's name in their interview.

So this irritation with people who make science accessible to the layperson runs deep, although I have to hope that this is changing, with a few truly first-rate scientists writing books to bring the latest research to the masses (Stephen Hawking, Sean Carroll, Brian Greene, Kip Thorne, Roger Penrose, Lee Smolin, and Lawrence Kraus come to mind).

It's a good thing.  Because to judge from a piece of research published this week in Advances in Political Psychology, there's more to be gained from popularizing science than just encouraging children to pursue science as a career; fostering a fundamental curiosity about nature is essential to eradicating biased thinking across the board.

Called "Science Curiosity and Political Information Processing," the paper, written by Dan Kahan of Yale University et al., looks at how best to move people from leaning on their own preconceived notions to evaluating the strength of claims based on evidence.  The research looked at how watching science documentaries engenders a curiosity about how the world works, and correlates with a lower likelihood of biases in arguments on subjects like anthropogenic climate change.

Kahan spoke with Chris Mooney, science writer over at The Washington Post, and explained what the research by his team had shown.  "It just so happened that, when we looked at the characteristics of [people who watch science documentaries], they seemed to be distinct politically," Kahan said.  "They stood out by being, as a group, less likely to feed the current polarization of political opinion on scientific matters such as climate change.  The data we’ve collected furnish a strong basis for viewing science curiosity as an important individual difference in cognitive style that interacts in a distinctive way with political information processing."

The most fascinating part of the research is that the difference doesn't seem to be related to scientific training, but scientific curiosity.  Having established a scale for measuring curiosity, Kahan et al. looked at both liberals and conservatives and assessed them for biased thinking.  Mooney writes:

Armed with the scientific curiosity scale, Kahan’s new study first demonstrated that while liberal Democrats and conservative Republicans with higher levels of proficiency in scientific thinking (which he calls “ordinary science intelligence”) tend to become more polarized and divided over the scientifically supported risks involved in both climate change and fracking, Democrats and Republicans with higher levels of science curiosity don’t.  Rather, for both groups, the more curious they are, the more their perceptions of the risks tend to increase...  [T]he study also contained an experiment, demonstrating that being possessed of heightened levels of scientific curiosity appeared to make political partisans more likely to read scientific information that went against their predilections.

The final statement is, to me, the most important.  An absolutely critical feature of the scientific view of the world is the ability to continually question one's base assumptions, and to look at the data with a skeptical eye.  And I am not using the word "skeptical" to mean "doubting," the way you hear people talk about "climate change skeptics" (a phrase that makes my skin crawl; no actual skeptic could consider the evidence about climate change questionable).  I am using "skeptical" in its literal sense, which means giving a rigorous look at the data from every angle, considering what it's telling you and examining the meaning of any trends that you happen to observe.  Which, of course, means entertaining the possibility that your prior understanding may be incorrect.  To me, there is no better indication of a truly scientific mind than when someone says, "Well, after examining the evidence, turns out I was wrong about that after all."

So we should be thankful for the popularizers, who follow in a long tradition of work by such greats as Sagan and Richard Feynman.  Children need to have their curiosity about the universe piqued early, and the flames fanned further by watching cool science shows that open their eyes to what a fascinating place we live in.  Think about what it would be like if we had a nation full of people who were committed to looking at the world through the lenses of evidence, logic, and critical thinking instead of prejudice and stubborn adherence to their own biases.

It's a nice possibility to think about, isn't it?