Background: Speech-in-noise perception is known to mature over the first 10 – 12 years of life. In this age range, children with language and/or reading difficulties have been reported to experience poor speech-in-noise perception compared with controls. However, the underlying aetiology for this finding is debated. Binaural Temporal Fine Structure sensitivity (bTFSs) is known to be beneficial for attending to sound sources in challenging environments. For young normal-hearing adults (YHNA), the upper frequency limit of bTFSs is known to be around 1400 Hz. Research has found the upper frequency limit of bTFSs to be significantly lower (worse) for typically developing children than for YHNA, with age being a significant predictor of the upper limit. If poor bTFSs contributes to impaired speech-in-noise perception in dyslexia (DYS), poorer bTFSs would be expected in DYS. In contrast, the Temporal Sampling (TS) theory of developmental dyslexia predicts that the perception of bTFS of speech may be preserved in children with dyslexia. By TS theory, reduced sensitivity to low-frequency envelope modulations is the core auditory impairment regarding DYS.

Methods: Binaural TFS sensitivity was measured using the Temporal Fine Structure-Adaptive Frequency (TFS-AF) test with 88 children aged 7-9.5 years (30 age-matched [CA], 20 male and 58 DYS, 31 male). Using a 2-up 1-down paradigm, the highest frequency at which interaural phase differences (IPD) of 30 degrees and 180 degrees could be distinguished from an IPD of 0 degrees was assessed.

Results: An LME model revealed no effect of group (F[1,44] = 0.18, p= .68), a significant effect of phase, with 30degrees lower than 180 degrees (F[1,44] = 214.83, p<.001), and no phase by group interaction (F[1,44] = 0.04, p= .84).

Conclusion: These results suggest that development of bTFSs is similar for DYS and CA children. Hence, the protracted developmental pattern of bTFSs was supported, with the upper frequency limit of bTFSs in children compared to YNHA being significantly lower (p < .001) for both levels of phase difference tested (30 and 180 degrees). A smaller frequency range of bTFSs may limit the benefit gained from spectral release from masking contributing to the known speech-in-noise deficit found in children when compared with adults. However, bTFSs was not found to be additionally impaired in DYS, supporting TS theory.

Funding: This work was supported by Fondation Botnar grant No. 6064, to U. Goswami.