Atypical cortical entrainment to speech in the right hemisphere underpins phonemic deficits in dyslexia

Abstract

Developmental dyslexia is a multifaceted disorder of learning primarily manifested by difficulties in reading, spelling, and phonological processing. Neural studies suggest that phonological difficulties may reflect impairments in fundamental cortical oscillatory mechanisms. Here we examine cortical mechanisms in children (6-12 years of age) with or without dyslexia (utilising both age- and reading-level-matched controls) using electroencephalography (EEG). EEG data were recorded as participants listened to an audio-story. Novel electrophysiological measures of phonemic processing were derived by quantifying how well the EEG responses tracked phonetic features of speech. Our results provide, for the first time, evidence for impaired low-frequency cortical tracking to phonetic features during natural speech perception in dyslexia. Atypical phonological tracking was focused on the right hemisphere, and correlated with traditional psychometric measures of phonological skills used in diagnostic dyslexia assessments. Accordingly, the novel indices developed here may provide objective metrics to investigate language development and language impairment across languages.

Infant‐directed speech to infants at risk for dyslexia: A novel cross‐dyad design

“…In their study, even though mothers were unaware of the fact that their infants were responding to a different interlocutor, they were sensitive to the disconnect between their own communicative behaviors and their infants' feedback, which resulted in adjustments in their pitch production to their infants. While we do not provide direct evidence that such disturbances are related to infants' risk of dyslexia in our study, there is ample evidence that neural coupling to speech is impaired in children and adults diagnosed with dyslexia (e.g., Di Liberto et al, 2018;Molinaro, Lizarazu, Lallier, Bourguignon, & Carreiras, 2016;Power, Colling, Mead, Barnes, & Goswami, 2016;Power, Mead, Barnes, & Goswami, 2013). To date, neural entrainment to continuous speech has not been tested in at-risk infants, but there is reduced discrimination of amplitude envelope rise time differences in at-risk infants .…”

A neural oscillations perspective on phonological development and phonological processing in developmental dyslexia

“…Further, recent studies with adults show that low‐frequency cortical oscillations (<8 Hz) also carry phonetic information directly (Di Liberto, O'Sullivan, & Lalor, ). This low frequency oscillatory phonetic information is represented atypically in children with developmental dyslexia (Di Liberto et al, ) at right hemisphere cortical locations. This provides direct evidence that atypical oscillatory entrainment to slower modulations (<10 Hz) has negative consequences for the development of phoneme awareness, as predicted by TS theory.…”

Phase resetting in human auditory cortex to visual speech

“…This phase alignment in turn determines systematic, stimulus-locked variations in neuronal activity, as indexed by fluctuations in broadband high-frequency activity. It was further shown that visual speech gestures enhance intelligibility by facilitating auditory cortical entrainment to the speech stream (Crosse, Butler and Lalor, 2015;Perrodin et al, 2015;Park et al, 2016Park et al, , 2018Di Liberto et al, 2018;Micheli et al, 2018). Here, we used iEEG recordings for a more direct examination of the neurophysiological mechanisms underlying visual enhancement of auditory cortical speech processing.…”

“…These rhythmic features of speech are critical for it to be intelligible (Shannon et al, 1995;Greenberg et al, 2003). Second, auditory cortex synchronizes its oscillations to the rhythm of heard speech, and the magnitude of this synchronization correlates with the intelligibility of speech (Ahissar et al, 2001;Luo and Poeppel, 2007;Ghinst et al, 2016;Di Liberto et al, 2018;Keitel, Gross and Kayser, 2018).…”