![\"v_research_16-10582-tyler-053\"](\"\/federal\/files\/2017\/01\/v_research_16-10582-TYLER-053.jpg\")
<\/a>Tyler Perrachione looks for the source of reading disorders, like dyslexia, in the brain. Photo (right) by Jackie Ricciardi.<\/em><\/p>\nIt\u2019s there, at the start of every conversation: the moment it takes your brain to adjust to an unfamiliar voice. It only lasts for a second or two, but in that brief time, your brain is thumbing its radio dial, tuning in to the unique pitch, rhythm, accent, and vowel sounds of a new voice. Once it is dialed in, the conversation can take off.<\/p>\n
This process is called rapid neural adaptation, and it happens constantly. New voices, sounds, sights, feelings, tastes, and smells all trigger this brain response. It is so effortless that we are rarely even aware it\u2019s happening. But, according to new work from Tyler Perrachione<\/a>, assistant professor at Boston University\u2019s College of Health & Rehabilitation Sciences: Sargent College<\/a>, and colleagues at the Massachusetts Institute of Technology<\/a> and Massachusetts General Hospital<\/a>, problems with neural adaptation may be at the root of dyslexia, a reading impairment that affects millions of Americans, including an estimated one-in-five to one-in-twenty schoolchildren. Their experiments, published December 21, 2016, in the journal Neuron<\/a><\/em>, are the first to use brain imaging to compare neural adaptation in the brains of people with dyslexia and those who read normally. The research was supported by the Lawrence Ellison Foundation<\/a>, the National Institutes of Health<\/a>, and the National Science Foundation<\/a>.<\/p>\n In the team\u2019s first experiment, volunteers without dyslexia were asked to pair spoken words with images on a screen while the researchers used functional magnetic resonance imaging (fMRI) to track their brain activity. The subjects tried the test two different ways. In one version, they listened to words spoken by a variety of different voices. In the second version, they heard the words all spoken by the same voice. As the researchers expected, the fMRI revealed an initial spike of activity in the brain\u2019s language network at the start of both tests. But during the first test, the brain continued revving with each new word and voice. When the voice stayed the same in the second test, the brain did not have to work as hard. It adapted.<\/p>\n But when subjects with dyslexia took the same tests, their brain activity never eased off. Like a radio that can\u2019t hold a frequency, the brain did not adapt to the consistent voice and had to process it fresh every time, as if it were new. The difference was even clearer in dyslexic children between ages six and nine, who were just learning to read; in a similar experiment, their brains didn\u2019t adapt at all to repeated words.<\/p>\n Perrachione and his colleagues wondered if the adaptation glitch was unique to spoken words, or if people with dyslexia would have trouble adapting to other kinds of stimuli, too. So they tried a second set of experiments, in which they showed subjects a repeating series of words, pictures, or faces, again using fMRI to look for the decline in brain activity that signals neural adaptation. Again, they found that the brains of people with dyslexia did not adapt\u2014or did not adapt as well\u2014as those without. \u201cWe found the signature everywhere we looked,\u201d says Perrachione.<\/p>\n The results suggest that dyslexic brains have to work harder than \u201ctypical\u201d brains to process incoming sights and sounds, requiring additional mental overhead for even the simplest tasks. \u201cWhat was surprising for me was the magnitude of the difference. These are not subtle differences,\u201d says Perrachione. The extra brainwork might not be noticeable most of the time, but it seems to have a singularly prominent impact on reading.<\/p>\n