Speech Perception and Sub-Cortical Processing of Speech in Noise in Children with Dyslexia

Abstract

Present study was carried out to investigate the sub-cortical processing of speech in quiet and in presence of noise in children with dyslexia and compared with typically developing children (N=29, age range = 8-12 years). Speech-evoked Auditory Brainstem Response (ABR) was elicited in quiet and noise with two different natural CV syllable (/da/ & /ba/) of 150 ms duration. Speech-in-noise (SPIN) performance was assessed using monosyllabic words in Indian English as behavioral measurement. Results showed that children with dyslexia had delayed latencies (poorer) of onset responses of speech-evoked ABR (wave V, wave A & slope of V/A complex) in the presence of noise for both speech syllables. Further, Mann-Whitney U test revealed statistically significant difference for wave V and wave A for quiet as well as noise condition for syllable /da/ at p < 0.05. However, there was no statistical significant difference found for syllable /ba/ across conditions (quiet vs noise). Sustained response includes amplitude of fundamental frequency (Fo) and harmonics (H2, H3 & H4). Result showed reduction in amplitude with increased higher harmonics. Descriptive statistics for SPIN test showed lower (poorer) mean score in children with dyslexia compared to typically developing children and Independent t-test revealed significant difference between two groups at p < 0.05. Spearman correlation between speech-evoked ABR and SPIN test suggested negative correlation for wave V and wave A and positive correlation with amplitude of harmonics in children with dyslexia. Present study concludes that children with dyslexia shows sub-cortical timing deficit in adverse listening condition and poor encoding ability of fundamental frequency compared to typically developing children.