Neurophysiological responses to phonological and temporal regularities in speech in dyslexic and typical readers

Objective

Sensitivity to sublexical speech features is important for successful reading development. Here we assessed the processing of formal (phonological) and temporal (syllable stress) sublexical speech regularities in typical and dyslexic readers.

Methods

We tested Dutch-speaking, typical and dyslexic adult readers in a passive EEG oddball paradigm, manipulating phonotactic probability (formal) and syllable stress (temporal) in Dutch pseudowords. We assessed the mismatch negativity (MMN) as a marker for experience-dependent change detection, as well as the associated phase-reset in the theta frequency band.

Results

Both deviant types elicited an MMN. Dyslexic readers exhibited reduced neural sensitivity to phonotactic, but not to stress regularities. Time-frequency analyses suggest distinct processes underlying change detection for different deviant types, with increased delta/theta inter-trial coherence (ITC) for formal deviants, which was enhanced in dyslexic readers, and a decrease for temporal deviants, which did not differ between groups.

Conclusion

Results suggest atypical sensitivity to phonological but not temporal speech regularities in dyslexic readers, and distinct oscillatory correlates underlying change detection for different deviant types.

Significance

This is the first study to simultaneously assess neural sensitivity to phonological and temporal regularities in Dutch adult dyslexic readers and highlights distinct change detection for different sublexical features.