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Dyslexia Doesn't Work the Way We Thought It Did

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Dyslexia is not just about reading, or even language. It’s about something more fundamental: How much can the brain adapt to what it has just observed? People with dyslexia typically have less brain plasticity than those without dyslexia, two recent studies have found.

Though the studies measured people’s brain activity in two different ways and while performing different tasks, researchers at the Hebrew University of Israel, reporting in eLife, and researchers from MIT, reporting in Neuron, both found that dyslexics’ brains did not adapt as much to repeated stimuli, including spoken words, musical notes, and faces.

Both sets of researchers found that people with dyslexia more quickly forget recent events. This type of memory is called incidental or implicit memory, and includes anything you didn't know you needed to remember when it happened. Because of how quickly their implicit memory fades, dyslexics' brains don't adapt as much after reading or hearing something repeatedly—which is perhaps why it is harder for their brains to process the words they read.

Your brain generally benefits from repetition because it relates a stimulus to what you've already experienced—like a note you have heard before or a face you’ve seen. Researchers can see this by measuring brain response with electroencephalography (EEG), a noninvasive way of measuring electrical activity in the brain by attaching electrodes to your scalp. Measured by EEG, people’s brain responses decrease when they’ve heard a repeated note. The brain gets more efficient with repetition: It knows something about the note already, so it doesn’t have to work as hard to capture all of its details. It’s a bit like when you see an animal and recognize right away that it’s a dog without having to catalogue all of the things that make it a dog. Your brain is efficient at recognizing dogs because you’ve seen them before.

SHORTER MEMORIES AND LESS ADAPTABILITY

In the Hebrew University study, led by Merav Ahissar, researchers gave subjects a musical task: The researchers played two different notes and asked which was higher. Previous research has found that people do better on this task when one of the notes is a repeat of a note they’ve heard recently. But Ahissar found that people with dyslexia did not benefit as much from the repetition. When a tone was repeated only three seconds after the "anchor" tone, they got some benefit, but not after nine seconds had elapsed. And when Ahissar’s team measured dyslexic people’s brain responses with EEG, their brain responses didn’t decrease. Their brains didn’t get any more efficient—they were less adaptable.

The MIT study, led by John Gabrieli, found similar results through a different experiment. Gabrieli used functional magnetic resonance imaging (fMRI) to measure people’s brain activity by measuring changes in blood flow in their brains. Instead of asking people to discriminate between musical notes, Gabrieli's team simply presented people with repeated things, including spoken words, written words, faces, and common objects like tables or chairs. During this task, dyslexic people's neural activity demonstrated less adaptation.

“It was a big surprise for us,” Gabrieli tells mental_floss, “because people with reading disorders don't typically have any problems with faces or objects.” Next, Gabrieli is curious to look into whether the effects of dyslexia on brain plasticity are limited to hearing and vision, or whether they also extend to other senses like touch and smell.

Together, these studies build a better understanding of how dyslexia works, and because the two studies found the same result with different methods, their results are more convincing than a single study alone. But they also raise a new question: Why is dyslexia mainly noticeable in reading if it affects other types of memories as well?

READING IS NEW—AND HARD, FROM THE BRAIN'S PERSPECTIVE

One theory is that reading is simply a difficult task. “We have a long evolutionary history in our brains for recognizing objects, recognizing faces," Gabrieli points out. That's not the case for reading. “There’s hardly a bigger challenge for brain plasticity than learning to read." More evolutionary time has allowed the brain to evolve redundant ways of accomplishing the same thing. Perhaps people with dyslexia are better at compensating for the memory gap for recognizing faces and spoken words because the brain has more alternate pathways for these processes than it does for reading.

Both Ahissar and Gabrieli are most excited that this research opens up new ways of studying—and perhaps someday treating—dyslexia. If dyslexia is a condition of reading and language only, as previously believed, “we cannot study it in animals,” Ahissar tells mental_floss. On the other hand, if it’s a condition of brain plasticity, we can—in fact, plasticity has been extensively studied in animals, and neuroscientists know a lot about it.

Someday, Gabrieli says, it may even be possible to develop drugs that would treat dyslexia by promoting brain plasticity, although researchers would have to be careful both practically and ethically.

“We can’t imagine developing a drug that would enhance language directly—that's too complicated," he notes. "But brain plasticity is something that neuroscientists are making amazing progress on.”

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The Brain Chemistry Behind Your Caffeine Boost
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Whether it’s consumed as coffee, candy, or toothpaste, caffeine is the world’s most popular drug. If you’ve ever wondered how a shot of espresso can make your groggy head feel alert and ready for the day, TED-Ed has the answer.

Caffeine works by hijacking receptors in the brain. The stimulant is nearly the same size and shape as adenosine, an inhibitory neurotransmitter that slows down neural activity. Adenosine builds up as the day goes on, making us feel more tired as the day progresses. When caffeine enters your system, it falls into the receptors meant to catch adenosine, thus keeping you from feeling as sleepy as you would otherwise. The blocked adenosine receptors also leave room for the mood-boosting compound dopamine to settle into its receptors. Those increased dopamine levels lead to the boost in energy and mood you feel after finishing your morning coffee.

For a closer look at how this process works, check out the video below.

[h/t TED-Ed]

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Anesthesia May Not Work the Way We Thought It Did
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You lie back, and a nurse fits a mask over your face. Somebody tells you to count backward from 100. Your eyelids grow heavy. The next thing you know, you’re waking up. We thought we knew why this happens, but new research published in the journal PLOS Computational Biology suggests we may have had it wrong.

The brains of people on general anesthesia are far quieter than those of folks who haven’t been drugged. Previous studies have suggested that this quieting happens when anesthesia interferes with conversations, or couplings, between different parts of our brain. Less information is exchanged, and the volume of the conversation drops.

It seemed like a solid enough explanation. But a team of German neuroscientists saw a possible flaw in the logic. The amount of information being exchanged often depends on the amount of information available, not on the strength of the connection.

To explore this puzzle further, they brought two female ferrets into the lab and hooked them up to brain activity monitors. (Ferret brains’ similarity to primates’ makes them a good lab substitute for humans, at least in initial studies.)

Both ferrets went through three rounds of anesthesia and recovery, receiving slightly more of the drug each time as the scientists watched their brains produce, process, and exchange information.

As in previous studies, the conversations in the ferrets’ brains were indeed more subdued while they were anesthetized. But it wasn’t interference that quieted their brains. The brain regions that ordinarily do the listening were just as active as usual. But the talkative brain regions seemed to have less to say. They were making and sending less information.

Lead author Patricia Wollstadt is a neuroscientist at the Brain Imaging Center at Goethe University Frankfurt. "The relevance of this alternative explanation goes beyond anesthesia research,” she said in a statement, "since each and every examination of neuronal information transfer should categorically take into consideration how much information is available locally and is therefore also transferable."

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