Authors: Pavlos Christodoulides , Victoria Zakopoulou , Katerina D. Tzimourta , Alexandros T. Tzallas , & Dimitrios Peschos.
Publication: Conference Paper (International Psychological Applications Conference and Trends). 2021
Dyslexia is one of the most frequent specific learning disorders which has often been associated with deficits in phonological awareness mainly caused by auditory and visual inabilities to recognize and discriminate phonemes and graphemes within words. Neuroimaging techniques like EEG recordings have been widely used to assess hemispheric differences in brain activation between students with dyslexia and their typical counterparts. Although dyslexia is a lifelong disorder which persists into adulthood, very few studies have been carried out targeting in adult population. In this study, we examined the brain activation differences between 14 typical (control group) and 12 university students with dyslexia (experimental group). The participants underwent two tasks consisting of 50 3-word groups characterized by different degrees of auditory and visual distinctiveness. The whole procedure was recorded with a 14-sensor sophisticated wearable EEG recording device (Emotiv EPOC+). The findings from the auditory task revealed statistically significant differences among the two sets of groups in the left temporal lobe in β, γ and δ rhythms, in the left occipital lobe in β rhythm, and in the right prefrontal area in α, β and γ rhythms, respectively. The students with dyslexia reported higher mean scores only in δ rhythm in the left temporal lobe, and in α, β and γ rhythms in the right prefrontal area. Concerning the visual task, statistically significant differences were evident in the left temporal lobe in β, γ rhythms, in the occipital lobe in α, β and δ rhythms, in the parietal lobe in β rhythm, and in the right occipital lobe in δ, β and γ rhythms. The students with dyslexia reported higher mean scores only in the δ rhythm of both the left and right occipital lobe. The results indicate that there are differences in the hemispheric brain activation of students with or without dyslexia in various rhythms in both experimental conditions, thus, shedding light in the neurophysiological discrepancies between the two groups. It also lays great emphasis on the necessity of carrying out more studies in adult population with dyslexia.
α, β and δ EEG bands were used to define unique brain activations and related possible phonological and reading impairments, in adults with dyslexia, during auditory and visual tasks. Such evidence would be relevant for the theory of magnocellular processing, which postulates the coexistence of auditory and visual processing deficits as indicative of a broadly distributed dysfunction in the “neural signature” of dyslexia.