Cognitive Abilities Contribute to Spectro-Temporal Discrimination in Children Who Are Hard of Hearing

Spectral ripple discrimination tasks have received considerable interest as potential clinical tools for use with adults and children with hearing loss. Previous results have indicated that performance on ripple tasks is affected by differences in aided audibility [quantified using the Speech Intelligibility Index, or Speech Intelligibility Index (SII)] in children who wear hearing aids and that ripple thresholds tend to improve over time in children with and without hearing loss. Although ripple task performance is thought to depend less on language skills than common speech perception tasks, the extent to which spectral ripple discrimination might depend on other general cognitive abilities such as nonverbal intelligence and working memory is unclear. This is an important consideration for children because age-related changes in ripple test results could be due to developing cognitive ability and could obscure the effect of any changes in unaided or aided hearing over time. The purpose of this study was to establish the relationship between spectral ripple discrimination in a group of children who use hearing aids and general cognitive abilities such as nonverbal intelligence, visual and auditory working memory, and executive function. It was hypothesized that, after controlling for listener age, general cognitive ability would be associated with spectral ripple thresholds and performance on both auditory and visual cognitive tasks would be associated with spectral ripple thresholds.

Children who were full-time users of hearing aids for at least 1 year (n = 24, ages 6 to 13 years) participated in this study. Children completed a spectro-temporal modulated ripple discrimination task in the sound field using their personal hearing aids. Threshold was determined from the average of two repetitions of the task. Participants completed standard measurements of executive function, nonverbal intelligence, and visual and verbal working memory. Real ear verification measures were completed for each child with their personal hearing aids to determine aided SII.

Consistent with past findings, spectro-temporal ripple thresholds improved with greater listener age. Surprisingly, aided SII was not significantly correlated with spectro-temporal ripple thresholds potentially because this particular group of listeners had overall better hearing and greater aided SII than participants in previous studies. Partial correlations controlling for listener age revealed that greater nonverbal intelligence and visual working memory were associated with better spectro-temporal ripple discrimination thresholds. Verbal working memory, executive function, and language ability were not significantly correlated with spectro-temporal ripple discrimination thresholds.

These results indicate that greater general cognitive abilities are associated with better spectro-temporal ripple discrimination ability, independent of children's age or aided SII. It is possible that these relationships reflect the cognitive demands of the psychophysical task rather than a direct relationship of cognitive ability to spectro-temporal processing in the auditory system. Further work is needed to determine the relationships of cognitive abilities to ripple discrimination in other populations, such as children with cochlear implants or with a wider range of aided SII.