Speech-Brain Frequency Entrainment of Dyslexia with and without Phonological Deficits

• Published in: Brain sciences 2020-11, Vol.10 (12), p.920
• Main Authors: Dushanova, Juliana, Lalova, Yordanka, Kalonkina, Antoaneta, Tsokov, Stefan
• Format: Article
• Language: English
• Subjects: auditory cortex; Auditory discrimination; Brain; Brain research; Children; Cognitive ability; Cognitive impairment; Cortex (auditory); Cortex (frontal); developmental dyslexia; Disability; Dyslexia; EEG; Entrainment; frequency oscillations; Frontal gyrus; Hemispheric laterality; inferior frontal cortex; Intelligence tests; Language; Linguistics; Neurodevelopmental disorders; Nonwords; Parietal lobe; Phonemics; Phonological memory; Phonology; Prosody; Reading comprehension; Semantics; Short term memory; Speech; Superior temporal sulcus; Temporal cortex; Temporal lobe; Visual discrimination
• ISSN: 2076-3425; 2076-3425
• DOI: 10.3390/brainsci10120920

Developmental dyslexia is a cognitive disorder characterized by difficulties in linguistic processing. Our purpose is to distinguish subtypes of developmental dyslexia by the level of speech-EEG frequency entrainment (δ: 1-4; β: 12.5-22.5; γ1: 25-35; and γ2: 35-80 Hz) in word/pseudoword auditory discrimination. Depending on the type of disabilities, dyslexics can divide into two subtypes-with less pronounced phonological deficits (NoPhoDys-visual dyslexia) and with more pronounced ones (PhoDys-phonological dyslexia). For correctly recognized stimuli, the δ-entrainment is significantly worse in dyslexic children compared to controls at a level of speech prosody and syllabic analysis. Controls and NoPhoDys show a stronger δ-entrainment in the left-hemispheric auditory cortex (AC), anterior temporal lobe (ATL), frontal, and motor cortices than PhoDys. Dyslexic subgroups concerning normolexics have a deficit of δ-entrainment in the left ATL, inferior frontal gyrus (IFG), and the right AC. PhoDys has higher δ-entrainment in the posterior part of adjacent STS regions than NoPhoDys. Insufficient low-frequency β changes over the IFG, the inferior parietal lobe of PhoDys compared to NoPhoDys correspond to their worse phonological short-term memory. Left-dominant 30 Hz-entrainment for normolexics to phonemic frequencies characterizes the right AC, adjacent regions to superior temporal sulcus of dyslexics. The pronounced 40 Hz-entrainment in PhoDys than the other groups suggest a hearing "reassembly" and a poor phonological working memory. Shifting up to higher-frequency γ-entrainment in the AC of NoPhoDys can lead to verbal memory deficits. Different patterns of cortical reorganization based on the left or right hemisphere lead to differential dyslexic profiles.