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Making it easier to learn to read
This press release is available in German.
To participate successfully in life, it is important to be able to read and write. Nevertheless, many children and adults have difficulties in acquiring these skills and the reason is not always obvious. They suffer from dyslexia which can have a variety of symptoms. Thanks to research carried out by Begoña Díaz and her colleagues at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, a major step forward has been made in understanding the cause of dyslexia. The scientists have discovered an important neural mechanism underlying dyslexia and shown that many difficulties associated with dyslexia can potentially be traced back to a malfunction of the medial geniculate body in the thalamus. The results provide an important basis for developing potential treatments.
People who suffer from dyslexia have difficulties with identifying speech sounds in spoken language. For example, while most children are able to recognise whether two words rhyme even before they go to school, dyslexic children often cannot do this until late primary school age. Those affected suffer from dyslexia their whole lives. However, there are also always cases where people can compensate for their dyslexia. "This suggests that dyslexia can be treated. We are therefore trying to find the neural causes of this learning disability in order to create a basis for improved treatment options," says Díaz. Between five and ten percent of the world's children suffer from dyslexia, yet very little is know about its causes.
This figure compares the situation in the brain of dyslexics and the control group. The blue area depicts the auditory cortices and the green area represents the medial geniculate bodies.
(Photo Credit: MPI for Human Cognitive and Brain Sciences)
Even though those affected do not lack intelligence or schooling, they have difficulties in reading, understanding and explaining individual words or entire texts. The researchers showed that dyslexic adults have a malfunction in a structure that transfers auditory information from the ear to the cortex is a major cause of the impairment: the medial geniculate body in the auditory thalamus does not process speech sounds correctly. "This malfunction at a low level of language processing could percolate through the entire system. This explains why the symptoms of dyslexia are so varied," says Díaz.
Under the direction of Katharina von Kriegstein, the researchers conducted two experiments in which several volunteers had to perform various speech comprehension tasks. When affected individuals performed tasks that required the recognition of speech sounds, as compared to recognize the voices that pronounced the same speech, magnetic resonance tomography (MRT) recordings showed abnormal responses in the area around the medial geniculate body. In contrast, no differences were apparent between controls and dyslexic participants if the tasks involved only listening to the speech sounds without having to perform a specific task. "The problem, therefore, has nothing to do with sensory processing itself, but with the processing involved in speech recognition," says Díaz. No differences could be ascertained between the two test groups in other areas of the auditory signalling path.
The findings of the Leipzig scientists combine various theoretical approaches, which deal with the cause of dyslexia and, for the first time, bring together several of these theories to form an overall picture. "Recognising the cause of a problem is always the first step on the way to a successful treatment," says Díaz. The researchers' next project is now to study whether current treatment programmes can influence the medial geniculate body in order to make learning to read easier for everyone in the long term.
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Could you please let me know
Could you please let me know if this research might have any bearing on a phenomenon found in dyslexics known as performance inconsistency?
I have recognized this problem in myself for many years now since our
daughter was diagnosed as being extremely intelligent and extremely dyslexic when she entered 7th grade in the Flemish school system. In 1973 I married a man from Antwerp, Belgium, and moved there shortly afterwards. I lived there with him for 32 years, raising our two children during this period.
From the day they were born, I spoke only English with the children, and my husband spoke only Dutch (or Flemish as it is often called in the Dutch-speaking part of Belgium). Despite taking (and passing) classes in Dutch, despite consulting speech therapists, and despite hearing this language spoken in my own home for 27 years, I have never been able to become fluent in it. At the dinner table when the children were still living with us, some days when the 3 of them were speaking Dutch together, I could understand everything they were saying, as though they were speaking English. The next day I might think that I understood, but when I made a comment, they would say, "that's not what we meant." And the following day,
I might not even be able to figure out what the topic of conversation was.
As just about everyone in Flanders speaks English fluently, when anyone (e.g. my husband's family or Flemish friends) wanted to speak with me, they would do so in English and then revert to speaking Dutch to each other. This has led to my feeling socially isolated, has led to depression, and now to divorce after 37 years of marriage. But more than enough of my story. I
detail it here just to give but one example of the devastating effects that dyslexia, and misunderstanding its causes, can have on a life.
Through my research, I have come to the opinion that most cases of dyslexia results not from problems with our external senses, but rather, as the recent MIT study begins to show, in the processing of sensory signals once they enter the brain. My hearing always tested in the normal range. And I am old enough to have been
taught phonetics and syllabication in elementary school. But while I understand these features intellectually, I don't hear them. Once a word is 5 or more letters, I begin to have trouble spelling it.
I can usually tell when a word is misspelled because it doesn't look right. I remember countless times while growing up asking my mother how to spell a word. And she would answer, "But Susan, it's spelled just the way it sounds," which gave me no clue as what the correct spelling might be.
I believe that my problems in learning a foreign language or spelling in my native one results from my brain's inability to process certain frequencies of human speech. I am also of the opinion that people can be dyslexic in any of their senses. Take for example, the lack of athletic ability or the inability to distinguish subtleties in flavors.
My question to you is whether or not you know of any research into this phenomenon of what special needs educator Richard Lavoie calls performance inconsistency. Why one day I can understand Dutch while on the majority of other days I cannot? Why a student can solve math problems on Monday but not on Thursday? Can a sort of lactic acid form between the neurons in the synapses? Or perhaps along the axons? Or does it have to do with the timing of the production of the neurotransmitters?
I would be most grateful for any insight you might be able to provide or to any directions you might be able to give me that deals with this occurrence.
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