Neural entrainment to rhythmic speech in children with developmental dyslexia

Abstract

A rhythmic paradigm based on repetition of the syllable “ba” was used to study auditory, visual, and audio-visual oscillatory entrainment to speech in children with and without dyslexia using EEG. Children pressed a button whenever they identified a delay in the isochronous stimulus delivery (500 ms; 2 Hz delta band rate). Response power, strength of entrainment and preferred phase of entrainment in the delta and theta frequency bands were compared between groups. The quality of stimulus representation was also measured using cross-correlation of the stimulus envelope with the neural response. The data showed a significant group difference in the preferred phase of entrainment in the delta band in response to the auditory and audio-visual stimulus streams. A different preferred phase has significant implications for the quality of speech information that is encoded neurally, as it implies enhanced neuronal processing (phase alignment) at less informative temporal points in the incoming signal. Consistent with this possibility, the cross-correlogram analysis revealed superior stimulus representation by the control children, who showed a trend for larger peak r-values and significantly later lags in peak r-values compared to participants with dyslexia. Significant relationships between both peak r-values and peak lags were found with behavioral measures of reading. The data indicate that the auditory temporal reference frame for speech processing is atypical in developmental dyslexia, with low frequency (delta) oscillations entraining to a different phase of the rhythmic syllabic input. This would affect the quality of encoding of speech, and could underlie the cognitive impairments in phonological representation that are the behavioral hallmark of this developmental disorder across languages.

Sensory theories of developmental dyslexia: three challenges for research

“…Therefore, the consistent timing difference could have cascading consequences for the optimal encoding of phonetic information by these children. Individual differences in preferred phase were indeed related to performance in a phoneme deletion task 100 . Importantly, different phase alignment between groups was not found in a visual speech control condition 100 .…”

“…Individual differences in preferred phase were indeed related to performance in a phoneme deletion task 100 . Importantly, different phase alignment between groups was not found in a visual speech control condition 100 . Nevertheless, RL-matched EEG studies are currently missing.…”

“…The same children were significantly impaired in neuronal entrainment to a rhythmic syllable stream presented at a rate of 2 Hz 100 . When hearing or seeing a speaker rhythmically repeating "ba, ba, ba", the children with dyslexia showed phase alignment at less informative temporal points in the incoming signal, which degraded speech representational quality 100 . The difference in preferred delta phase between the groups was 0.16 radians at 2 Hz, which is the equivalent of 12.8 ms, an interval within the phonetically important 40 ms window identified earlier by RAP theory 58 .…”

Neural encoding of the speech envelope by children with developmental dyslexia

“…Recent studies with adults and children with developmental dyslexia have consistently reported atypical neural activity related to auditory processing (Abrams et al, 2009, Lehongre et al, 2011, Poelmans et al, 2012, Hornickel and Kraus, 2013, Power et al, 2013, Lizarazu et al, 2015). However, none of these recent auditory studies has used a reading level (RL) match control group, an important research design for helping to distinguish cause from effect in studies of developmental disorders (Goswami, 2003).…”

Atypical right hemisphere response to slow temporal modulations in children with developmental dyslexia

“…Power et al (2013) administered the AV rhythmic speech paradigm developed by Power et al (2012) to English-speaking children with dyslexia. They reported that, compared to age-matched control children, the children with dyslexia showed a different preferred phase of entrainment in the delta band, in response to both the auditory and the auditory-visual stimulus streams.…”