Binaural responses to a speech syllable are altered in children with hearing loss: Evidence from the frequency-following response.

Background & Rationale: In prior work using non-speech stimuli, children with hearing loss show impaired perception of binaural cues and no significant change in cortical responses to bilateral versus unilateral stimulation. Aims of the present study were to: 1) identify bilateral responses to envelope and spectral components of a speech syllable using the frequency-following response (FFR), 2) determine if abnormalities in the bilateral FFR occur in children with hearing loss, and 3) assess functional consequences of abnormal bilateral FFR responses on perception of binaural timing cues.

Methods: A single-syllable speech stimulus (/dα/) was presented to each ear individually and bilaterally. Participants were 9 children with normal hearing (M = 12.1 ± 2.5 years) and 6 children with bilateral hearing loss who were experienced bilateral hearing aid users (M = 14.0 ± 2.6 years). FFR temporal and spectral peak amplitudes were compared between listening conditions and groups using linear mixed model regression analyses. Behavioral sensitivity to binaural cues were measured by lateralization responses as coming from the right or left side of the head.

Results: Both temporal and spectral peaks in FFR responses increased in amplitude in the bilateral compared to unilateral listening conditions in children with normal hearing. These measures of "bilateral advantage" were reduced in the group of children with bilateral hearing loss and associated with decreased sensitivity to interaural timing differences.

Conclusion: This study is the first to show that bilateral responses in both temporal and spectral domains can be measured in children using the FFR and is altered in children with hearing loss with consequences to binaural hearing.