Elizabeth Huber – UW News

Brains of blind people adapt to sharpen sense of hearing, study shows

Kim Eckart — Mon, 22 Apr 2019 19:20:07 +0000

People who are visually impaired rely on other senses to interpret their surroundings. A pair of studies from the ��Ӱ�Ӵ�ý shows how the brains of blind people adapt to process information.

Research has shown that people who are born blind or become blind early in life often have a more nuanced sense of hearing, especially when it comes to musical abilities and tracking moving objects in space (imagine crossing a busy road using sound alone). For decades scientists have wondered what changes in the brain might underlie these enhanced auditory abilities.

Now, a pair of research papers published the week of April 22 from the ��Ӱ�Ӵ�ý — in the , the other in the — use to identify two differences in the brains of blind individuals that might be responsible for their abilities to make better use of auditory information.

“There’s this idea that blind people are good at auditory tasks, because they have to make their way in the world without visual information. We wanted to explore how this happens in the brain,” said , a UW professor of psychology and the senior author on both studies.

Instead of simply looking to see which parts of the brain were most active while listening, both studies examined the sensitivity of the brain to subtle differences in auditory frequency.

“We weren’t measuring how rapidly neurons fire, but rather how accurately populations of neurons represent information about sound,” said , a graduate student in the UW Department of Psychology and lead author on the Journal of Neuroscience paper.

That found that in the auditory cortex, individuals who are blind showed narrower neural “tuning” than sighted subjects in discerning small differences in sound frequency.

“This is the first study to show that blindness results in plasticity in the auditory cortex. This is important because this is an area of the brain that receives very similar auditory information in blind and sighted individuals,” Fine said. “But in blind individuals, more information needs to be extracted from sound — and this region seems to develop enhanced capacities as a result.

“This provides an elegant example of how the development of abilities within infant brains is influenced by the environment they grow up in.”

The second study examined how the brains of people who are born blind or become blind early in life — referred to as “early blind” individuals — represent moving objects in space. The research team showed that an area of the brain called the hMT+ — which in sighted individuals is responsible for tracking moving visual objects — shows neural responses that reflect both the motion and the frequency of auditory signals in blind individuals. This suggests that in blind people, area hMT+ is recruited to play an analogous role — tracking moving auditory objects, such as cars, or the footsteps of the people around them.

The paper in the Journal of Neuroscience involved two teams — one at the UW, the other at the University of Oxford in the United Kingdom. Both teams measured neural responses in study participants while participants listened to a sequence of Morse code-like tones that differed in frequency while the fMRI machine recorded brain activity. The research teams found that in the blind participants, the auditory cortex more accurately represented the frequency of each sound.

“Our study shows that the brains of blind individuals are better able to represent frequencies,” Chang said. “For a sighted person, having an accurate representation of sound isn’t as important because they have sight to help them recognize objects, while blind individuals only have auditory information. This gives us an idea of what changes in the brain explain why blind people are better at picking out and identifying sounds in the environment.”

Left: Researchers began by measuring responses in the auditory cortex to find a map of how frequency responses were represented in the brain. The warm colors represent regions of the brain that showed the greatest response to low-pitched tones, while blue colors represent regions that responded more to high-pitched tones.
Right: When researchers examined the range of frequencies each vertex of the brain was selective to, they found tuning tended to be narrower for blind individuals, which may underlie the enhanced ability of blind individuals to pick out and identify sounds in the environment. Photo: Kelly Chang/U. of Washington

The Proceedings of the National Academy of Sciences study examined how the brain’s “recruitment” of the hMT+ region might help blind people track the motion of objects using sound. Participants once again listened to tones that differed in auditory frequency, but this time the tones sounded like they were moving. As has been found in previous studies, in blind individuals the neural responses in area hMT+ contained information about the direction of motion of the sounds, whereas in the sighted participants these sounds did not produce significant neural activity.

By using sounds that varied in frequency, the researchers could show that in blind individuals, the hMT+ region was selective for the frequency as well as the motion of sounds, supporting the idea that this region might help blind individuals track moving objects in space.

“These results suggest that early blindness results in visual areas being recruited to solve auditory tasks in a relatively sophisticated way,” Fine said.

This study also included two sight-recovery subjects — individuals who had been blind from infancy until adulthood, when sight was restored via surgery in adulthood. In these individuals, area hMT+ seemed to serve a dual purpose, capable of processing both auditory and visual motion. The inclusion of people who used to be visually impaired lends additional evidence to the idea that this plasticity in the brain happens early in development, Fine said, because the results show that their brains made the shift to auditory processing as a result of their early-life blindness, yet maintains these abilities even after sight was restored in adulthood.

According to Fine, this research extends current knowledge about how the brain develops because the team was not only looking at which regions of the brain are altered as a result of blindness, but also examining precisely what sort of changes — specifically, sensitivity to frequency —might explain how early blind people make sense of the world. As one of the study participants described it, “You see with your eyes, I see with my ears.”

Both studies were funded by the National Eye Institute and the National Institutes of Health. The Proceedings of the National Academy of Sciences study was co-authored by of the UW and Fang Jiang of the University of Nevada, Reno. The Journal of Neuroscience study was co-authored by Chang and Huber, as well as Ivan Alvarez, Aaron Hundle and Holly Bridge of the University of Oxford.

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For more information, contact Fine at ionefine@uw.edu or 206-685-6157, or Chang at kchang4@uw.edu.

‘Teachers are brain engineers’: UW study shows how intensive instruction changes brain circuitry in struggling readers

Kim Eckart — Thu, 14 Jun 2018 16:47:37 +0000

A study from the ��Ӱ�Ӵ�ý found that when children with reading difficulties underwent an intensive tutoring program, their brains’ white matter strengthened, and their reading skills improved.

The early years are when the brain develops the most, forming neural connections that pave the way for how a child — and the eventual adult — will express feelings, embark on a task, and learn new skills and concepts. Scientists have even theorized that the anatomical structure of neural connections forms the basis for how children identify letters and recognize words. In other words, the brain’s architecture may predetermine who will have trouble with reading, including children with dyslexia.

But teaching can change that, a new ��Ӱ�Ӵ�ý study finds.

Using MRI measurements of the brain’s neural connections, or “white matter,” UW researchers have shown that, in struggling readers, the neural circuitry strengthened — and their reading performance improved — after just eight weeks of a specialized tutoring program. The , published June 8 in Nature Communications, is the first to measure white matter during an intensive educational intervention and link children’s learning with their brains’ flexibility.

“The process of educating a child is physically changing the brain,” said , an assistant professor in both the UW Department of Speech and Hearing Sciences and the Institute for Learning & Brain Sciences (I-LABS). “We were able to detect changes in brain connections within just a few weeks of beginning the intervention program. It’s underappreciated that teachers are brain engineers who help kids build new brain circuits for important academic skills like reading.”

Jason Yeatman, an assistant professor in the UW Department of Speech and Hearing Sciences, shows an illustration of the brain in his office at I-LABS. Mark Stone/U. of Washington Photo: Mark Stone/U. of Washington

The study focused on three areas of white matter — regions rich with neuronal connections — that link regions of the brain involved in language and vision.

“We tend to think of these connections as being fixed,” said co-author , a UW postdoctoral researcher. “In reality, different experiences can shape the brain in dramatic ways throughout development.”

After eight weeks of intensive instruction among study participants who struggled with reading, two of those three areas showed evidence of structural changes — a greater density of white matter and more organized “wiring.” That plasticity points to changes brought about by the environment, indicating that these regions are not inherently inflexible structures. They reorganize in response to experiences children have in the classroom.

, a learning disorder that affects the ability to read and spell words, is the most common language-related learning disability. While estimates vary, between 10 to 20 percent of the population has some form of dyslexia. There is no quick and simple cure, and without intervention, children with dyslexia tend to struggle in school as the need for literacy skills increases over time.

See a related story in (may be behind a paywall).

Yeatman, who launched the at I-LABS, conducted the study during the summers of 2016 and 2017, when a total of 24 children, ages 7 to 12, participated in a reading intervention program offered by Lindamood-Bell Learning Centers. The company did not fund the study but provided the tutoring services for free to study participants. The participants’ parents had reported that their child either struggled with reading or had been diagnosed with dyslexia.

Over eight weeks, the children received one-on-one instruction for four hours a day, five days a week. They took a series of reading tests before and after the tutoring program and underwent four MRI scans and behavioral evaluation sessions at the beginning, middle and end of the eight-week period. A control group of 19 children with a mixture of reading skill levels participated in the MRI and behavioral sessions but did not receive the reading intervention.

The researchers used measurements to determine the density of three areas of white matter — areas that contain nerve fibers and connect different specialized processing circuits to each other. Specifically, they looked at the rate at which water diffuses within the white matter: A decline in the rate of diffusion indicates that additional tissue has formed, which allows information to be transmitted faster and easier.

This illustration of the brain shows the arcuate fasciculus (green); inferior longitudinal fasciculus (blue); and posterior callosal connections (pink).

The analysis focused on the left arcuate fasciculus, which connects regions where language and sounds are processed; the left inferior longitudinal fasciculus, where visual inputs, such as letters on a page, are transmitted throughout the brain; and the posterior callosal connections, which link the two hemispheres of the brain.

Subjects in the control group showed no changes in diffusion rates or structure between MRI measurements. But for subjects who took part in the tutoring program, reading skills improved by an average of one full grade level. In the majority of these subjects, diffusion rates decreased in the arcuate and inferior longitudinal fasciculus. For the few children who showed no significant decline in diffusion by MRI, Yeatman said there could be compounding differences in individual capacities for brain plasticity, age of the participants (younger brains may be more susceptible to change than slightly older ones) or other factors.

The callosal connections showed no changes between treatment and control groups, results that support past research suggesting that this structure, though relevant for reading acquisition, may already be mature and stable by age 7, Yeatman said.

Just what kind of tissue was created among reading program participants is likely to be the subject of future study, the authors said. For example, the measurements might be picking up on increases in the number or size of certain types of cells that help nourish and maintain the white matter, or on added insulation for existing neural connections, Huber said. The challenge with MRI data, Yeatman pointed out, is that they reflect an indirect measurement — not a hands-on examination of the brain.

But the structure of this experiment underscores the importance of the findings, he added: Children participated in a tightly controlled, short-term educational intervention, with measurable, identifiable growth in brain tissue from start to finish.

“Much of what we know about brain plasticity comes from research done in animals,” Yeatman said. “The beauty of educational interventions is that they provide a means to study fundamental questions about the link between childhood experiences, brain plasticity and learning, all while giving kids extra help in reading.”

Yeatman believes the findings can extend to schools. Teachers have the potential to develop their students’ brains, regardless of whether they have the resources to provide individualized instruction for each student in their class.

“While many parents and teachers might worry that dyslexia is permanent, reflecting intrinsic deficits in the brain, these findings demonstrate that targeted, intensive reading programs not only lead to substantial improvements in reading skills, but also change the underlying wiring of the brain’s reading circuitry,” Yeatman said.

Other authors on the paper were , a graduate student at I-LABS, and , a data science fellow at the UW eScience Institute. The study was funded by a grant from the National Science Foundation.

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For more information, contact Yeatman at 206-685-3934 or jyeatman@uw.edu.

Grant number: 1551330��