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

Abstract

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.

Functional Connectivity in Developmental Dyslexia during Speed Discrimination

“…The rewiring of the neural network suggests that the low-frequency transitions in theta/beta frequencies reset the neural activity occurring at γ frequencies as for selective attention [89], while the rewire at the high-frequency transitions in β/γ1 frequencies might be a more general process across other modalities. The visual stimuli might expose changes in visuospatial attention on a neural level of visual areas, which sampling rate for visual search is in the range of low γ frequencies and not the much slower δ/θ rate that shows no deficit [13,58,85]. The controls and the post-D in γ1-frequency range had moderately integrated and segregated networks for a low-speed condition and more segregated in both groups than the pre-D.…”

“…They scored ≥98 points in their nonverbal intelligence test [63]. Children who had difficulty reading, along with accuracy or speed in reading subtests of the DDE-2 battery and the "Reading Abilities" battery below the norm with a standard deviation of standardized data of normally reading children were included in the dyslexic group [85]. Children, participating in the study as controls, were recruited from the schools of the dyslexics.…”

Improving non‐native duration contrast with dichotic training in dyslexic and non‐dyslexic individuals

“…Despite accumulating evidence for atypical processing of slow rate changes during speech processing in DYS, temporal processing in the high-frequency ranges has also been documented. For instance, a lack of LH-specialization for fast oscillations (Lehongre, Morillon, Giraud, & Ramus, 2013) and reduced leftward lateralization for high-frequency entrainment (Dushanova, Lalova, Kalonkina, & Tsokov, 2020) have been reported in developmental DYS. Dichotic stimulation might be an appropriate method to improve the English long/short vowel contrast (e.g., /i:/À/ɪ/) processing in French speakers, notably by promoting hemispheric complementarity for duration processing.…”

“…Despite accumulating evidence for atypical processing of slow rate changes during speech processing in DYS, temporal processing in the high‐frequency ranges has also been documented. For instance, a lack of LH‐specialization for fast oscillations (Lehongre, Morillon, Giraud, & Ramus, 2013) and reduced leftward lateralization for high‐frequency entrainment (Dushanova, Lalova, Kalonkina, & Tsokov, 2020) have been reported in developmental DYS.…”

Latest Advances in Human Brain Dynamics

“…Developmental dyslexia is a cognitive linguistic disorder. The study by Dushanova et al [ 1 ] attempted to distinguish subtypes of developmental dyslexia based on the association of speech envelope and electroencephalography (EEG) frequency entrainment adopting a word/pseudoword auditory discrimination experimental paradigm. The main findings of this study revealed aberrant frequency-dependent entrainments of distinct brain areas related to the task differentiating phonological dyslexia from visual dyslexia.…”