Atypical cortical encoding of speech identifies children with Dyslexia versus Developmental Language Disorder

Abstract

Slow cortical oscillations play a crucial role in processing the speech envelope, which is perceived atypically by children with Developmental Language Disorder (DLD) and developmental dyslexia. Here we use electroencephalography (EEG) and natural speech listening paradigms to identify neural processing patterns that characterize dyslexic versus DLD children. Using a story listening paradigm, we show that atypical power dynamics and phase-amplitude coupling between delta and theta oscillations characterize dyslexic and DLD children groups, respectively. We further identify EEG common spatial patterns (CSP) during speech listening across delta, theta and beta oscillations describing dyslexic versus DLD children. A linear classifier using four delta-band CSP variables predicted dyslexia status (0.77 AUC). Crucially, these spatial patterns also identified children with dyslexia in a rhythmic syllable task EEG, suggesting a core developmental deficit in neural processing of speech rhythm. These findings suggest that there are distinct atypical neurocognitive mechanisms underlying dyslexia and DLD.

Infant low-frequency EEG cortical power, cortical tracking and phase-amplitude coupling predicts language a year later.

“…The amount of theta PSD power increased relative to the amount of delta PSD power as our sample aged from 4- to 11- months. For comparison, the child modelling using EEG recorded from children with and without dyslexia aged around 9 years showed that a higher theta/delta ratio was associated with poorer language outcomes (27).…”

“…As PAC did not show strong development with age, no strong predictions were made. However, given the DLD modelling data noted earlier (27), poorer PAC may be linked to worse language outcomes. Further, a higher theta/delta power ratio may be linked to worse language outcomes (27).…”

“…However, given the DLD modelling data noted earlier (27), poorer PAC may be linked to worse language outcomes. Further, a higher theta/delta power ratio may be linked to worse language outcomes (27). In Araújo et al, preprint, higher ratios in the dyslexic group were not driven by group differences in either delta or theta power per se, but by their joint dynamics.…”

“…LFP centre frequencies were filtered from 2 to 8 Hz, in 1 Hz steps with a 2 Hz bandwidth, and HFA centre frequencies were filtered from 17.5 Hz to 42.5 Hz, in 5 Hz steps with a 5 Hz bandwidth before a normalised modulation index value was computed for each channel (19,42). The EEG bands were defined as delta (2-4 Hz), theta (4-8 Hz) beta (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and gamma (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45). The channel exhibiting the strongest nMI, within predefined phase and amplitude band groupings (delta/beta, delta/gamma, theta/beta, theta/gamma), was taken forward for further analysis.…”

“…Accordingly, both PAC and the theta/delta power ratio in infants may predict subsequent language development, in addition to low-frequency cortical tracking. The developmental theoretical framework encapsulated by TS theory informed Araujo et al's (27) modelling (Pre-print), and predicts that cortical tracking within specific low-frequency bands (i.e. delta, 1-4 Hz and theta, 4-8 Hz) and their interactive dynamics is central to language acquisition (4,28,29).…”