Dyslexic Frequency Signatures in Relaxation and Letter Writing

Dyslexia is a neurological disorder with impact to a child’s confidence in life. It can be reduced if detected at an early stage. This difficulty with learning due to impairment to the left hemisphere of the brain, associated with language processing, is often misunderstood as being lazy. Electroencephalography (EEG) is one of technologies popularly employed to study dyslexia. Most previous works on dyslexia are either based on subjective or psychometric methods and focused on reading and spelling. Our research here aims to study the brain activity of the dyslexic children during relaxation and letter writing, by comparing the EEG frequency content between normal and dyslexic children. The uniqueness and credibility of our experiment are tasks being adopted from the diagnostic manual of the Dyslexia Association of Malaysia (DAM). Also, the electrode placement has been optimized to four, i.e. C3, C4, P3 and P4 along the neurological pathway for writing activity. It is found that the frequency ranges of EEG recorded during relaxation is 8–13 Hz, in the alpha-subband and that during non-segmented writing is 13–28 Hz, in beta-subband. In relaxed state, the EEG amplitude indicates that the normal HighIQ group is more relaxed than the dyslexic Capable group. Higher activity is found in the frequency pattern of EEG during the writing tasks than during relaxation for both normal HighIQ/dyslexic Capable group. The dyslexic Capable group is observed to exert more stress to do the task. The two peaks in the alpha and beta-subband in the Fast Fourier Transform (FFT) envelope of EEG from all groups can be explained by pausing to think in between writing. Based on these peaks, the normal group shows use of high neural resources at the beginning of the task while the dyslexic group shows that at the beginning and end of the task. It is also observed that the EEG bandwidth is wider for the normal HighIQ/dyslexic Capable group than the normal AverageIQ/dyslexic Average group.

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