Temporal processing of slow amplitude modulations and consonant in noise perception in children using cochlear implants

The aim of this study was to evaluate the development of auditory temporal processing and speech in noise abilities in children using cochlear implants (CI) in order to identify potential predictors of cochlear implantation success in childhood.

We included 25 children aged 5 to 12 years, implanted before the age of 4 years. They performed several psychophysical tasks measuring 1) AM detection thresholds for a slow modulation rate (8 Hz), 2) AM masking, 3) consonant identification thresholds in a stationary speech-shaped noise. The AM tasks were directly delivered through one electrode of the implant using a research interface provided by Advance Bionics (direct stimulation). Moreover, children with CI completed standardized assessments of receptive vocabulary, communication skills, non-verbal reasoning, non-verbal working memory and the level of parental education was registered. Their perceptive thresholds were compared to two groups of children with normal-hearing (NH), matched either in chronological age, or in hearing age.

The results showed no effect of age on 8Hz-AM detection thresholds and children using CIs who were electrically stimulated showed better AM detection thresholds than acoustically stimulated children with NH. However, children using CIs showed significantly the worst thresholds in the masking condition. Children with CIs showed poorer consonant identification thresholds in noise compared to children with NH. Finally, regression analyses indicated that the only significant predictor of consonant identification in noise was parental education. No relationship between AM detection thresholds and consonant perception in noise was observed.

In conclusion, the processing of masked AM in children using CIs is not similar to their NH peers of the same chronological or hearing age. Their ability to identify consonants in stationary noise was impaired but not significantly related to AM processing at 8Hz. Further studies are required to assess the value of other psychoacoustic tests that can be used clinically to better predict language learning in children using CIs.