(40) Research on Brain: reading.

Research on BRAIN month continues with the another indispensable gift that human brain offers us, amongst other skills – and that is READING. The Experienced Researcher at the 4th top young leading university in the world Maastricht University, Dr. Gojko Žarić will explain us how is it that we end up re-a-ding… Finally, I get to understand what are these machines on a Researcher’s head doing :):)

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Dr. Gojko Zaric

Can you read? How do you do that?

Humans read and write for about 5000 years. It appears that the reading relies on the brain areas that serve other functions, such as vision, hearing and language, rather than reading alone. But things get more complicated with other higher cognitive functions such as, the attention – a crucial factor in successful reading.

 

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Figure 1. Possibly the earliest known writing. Summer pictographic writing on the limestone tablet from Kish dated ~3500 BC (Source: Wikipedia).

This means that a large number of brain areas have to cooperate to allow us to read (one example of these areas is in  Figure 2). Thus, as reading is a complex cognitive function, it is not surprising that 1-2 in every 20 children have trouble mastering this skill. In other words, in every classroom there is at least one child struggling with reading due to a specific learning disability with neuro-biological root. These children suffer from developmental dyslexia. In my research I am looking at brain responses of children and adults to reading related materials and tasks.

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Figure 2. One modern day view of the brain areas involved in reading (Source: Dehaene, Reading in the Brain, 2009).

Written language consists of arbitrary visual forms, i.e. letters. that the certain society relates to the speech sounds of its language. Speech sounds are distinct units of the spoken language that differentiate between the words (e.g. mug, bug, rug). If the letters represent distinct speech sounds we call the script alphabetic (Latin, Greek, Cyrillic, Hangul, Armenian and Georgian) A more loose definition of alphabetic scripts includes script such as abjad in which commonly only the consonants are written (Arabic and Hebrew), syllabic (Japanese Katakana script), and abugida scripts in which the vowel does not have its own symbol but is represented by changing the letter symbol of the consonant (e.g. Indic, Ethiopic, Canadian Aboriginal). Another group of scripts are logographic scripts, such as Chinese, in which visual symbols already represent meaningful units of language (Figure 3).

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Figure 3. Examples of different scripts: 1) Alphabet – Dutch 2) Syllabic – Japanese Katakana 3) Abjad – Hebrew 4) Abugida – Ethiopic 5) Alphabet – Serbian Cyrillic and Latin 6) Logographic – Chinese standard and modern simplified (examples).

Thus, a child learning to read an alphabetic script first has to learn to connect letters and corresponding speech sounds, e.g. letter “m” to the speech sound /m/ in the words “mug”, “drum”… My research topic (remember what we called a “Research question” part on do-your-own-little Research?) is how a child’s brain builds up letter-speech sound connections and how it automatizes them to allow children to move to the next stages of the reading development. Next, my research also concerns the reading stage in which these connections are made and children can recognize words as units without having to read them letter by letter.  Furthermore, I am interested in what brain responses differ between children with and without reading problems. In other words, can I find which brain areas or which cognitive functions are not cooperating as supposed to.

To investigate these questions we can use different neuro-scientific methods such as electroencephalography, functional and structural magnetic resonance imaging.

Electroencephalography (EEG) tells us, with the millisecond precision when the brain responds to a certain stimulus. For example, we can present readers with the letters and speech sounds that match or mismatch (Figure 4, middle row) and we can investigate how is the brain responding in these two conditions and if the brains of dyslexic children produce different responses. In another task, we can measure  their responses while they read words or meaningless letter-like false font strings (Figure 4, bottom row). We can then analyze, for example, amplitudes and latencies of the brain responses. We can also analyze how is signal measured at the back of the head related to the signal measured at the front of the head to see if these signals come from the brain areas that cooperate or not. And many more possibilities for an analysis of the EEG data are available…

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Figure 4. Examples of an EEG measurement during letter-speech sound integration and word reading task.

We can use functional magnetic resonance imaging (fMRI) to see where in the brain are the areas that get more/less activated during letter-speech sound integration or word reading (example in Figure 2 is based on multiple studies with various tasks). With this method we can see that children and adult readers activate the same brain network during reading, but regions that are involved in letter-speech sound integration are activated more in children, while regions involved in fast recognition of words as units are activated more in adults.

We can also look at the white matter of the brain using magnetic resonance imaging, by employing different imaging technique, diffusion weighted imaging (Figure 5). White matter contains the highways of the brain, large bundles of the neuronal axons through which the signals travel between different brain areas. The integrity of the white matter can develop differently over time in dyslexic and typical readers. On the other hand, reading can influence white matter development, i.e. the more the certain neuronal bundles are used, the more structured they become.

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Figure 5. Diffusion weighted image of the white matter of the human brain (Source: Wikipedia).

Thus neuroscience offers multiple methods to look at the typical and atypical reading development. These methods can be combined with reading trainings to examine the benefits of the training at both behavioral and neural level. The coupling of behavioral and neural changes with reading training is not only scientifically important as it informs us which brain areas serve which functions, but it is foremost important for the children with reading problem, as it may be a sign that the changes are long-lasting.

If this short introduction made you interested in the research of reading and dyslexia, you can check my ResearchGate page or webpage http://gorka.science/, made by my collaborator, Dr. Gorka Fraga González from University of Amsterdam, where you can find our scientific papers on these topics. You can visit our Maastricht University based research group page to find out more on different reading, speech and language related research.

Post written by Gojko Žarić, M-BIC, Maastricht University

With love for Research,

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