Posts tagged dyslexia

August 06, 2012

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.

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. © MPI for Human Cognitive and Brain Sciences

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. 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.

ScienceDaily (June 7, 2012) — Increasing the spacing between characters and words in a text improves the speed and quality of dyslexic children’s reading, without prior training. They read 20% faster on average and make half as many errors. This is the conclusion reached by a French-Italian research team, jointly headed by Johannes Ziegler of the Laboratoire de Psychologie Cognitive (CNRS/Aix-Marseille Université).

Increasing the spacing between characters and words in a text improves the speed and quality of dyslexic children’s reading, without prior training. (Credit: © Johannes Ziegler, courtesy CNRS)

These results were published 4 June 2012 in the Proceedings of the National Academy of Science (PNAS). In parallel, the team has developed an iPad/iPhone application, available under the name “DYS.” It allows both parents and children to modify the spacing between letters and thus test the benefits of these changes on reading. This will enable researchers to collect large-scale, real time data, which they will then analyze and study.

Dyslexia is a learning disability that impairs an individual’s capacity to read and is linked to difficulty in identifying letters, syllables and words — despite suitable schooling and in the absence of intellectual or sensorial deficiencies. Dyslexia, which often causes writing problems, affects on average one child in every class and 5% of the world’s population.

In this study, the researchers tested the effects of letter spacing on the reading ability of 54 dyslexic Italian and 40 dyslexic French children aged between 8 and 14 years. The children had to read a text composed of 24 sentences, in which the spacing was either normal or wider than usual. The results showed that wider spacing enabled the children to improve their reading both in terms of speed and precision. On average, they read 20% faster and made half as many errors. This progress could stem from the fact that dyslexic children are particularly sensitive to “perceptual crowding,” in other words the visual masking of each individual letter by those surrounding it. The results of this study show that this crowding effect may be reduced by spacing letters apart.

This finding opens interesting perspectives in the field of dyslexia treatment techniques. Indeed, reading better means reading more — yet it takes one year for a dyslexic child to read what a “normal reader” reads in two days. This is because reading can be “torture” for dyslexic children, whose decoding difficulties cause to stumble, putting them off reading on a regular basis. The researchers have found a simple and efficient “trick” that helps these children break the vicious circle and correctly read more words in less time.

An iPad/iPhone application known as “DYS” has been developed in parallel with these research results by Stéphane Dufau, CNRS research engineer at the Laboratoire de Psychologie Cognitive. Available initially in French and English and downloadable free of charge from Apple Store, it enables both parents and children to adjust the spacing between letters and to test the benefits of such modifications on reading. The researchers for their part hope to be able to collect large-scale data that will allow them to quantify and analyze whether optimal spacing exists as a function of the subject’s age and reading level.

Download available: http://itunes.apple.com/us/app/dys-help-people-with-dyslexia/id529867852?mt=8

Source: Science Daily