Although the primary damage associated with sensorineural hearing loss lies in the cochlea, its consequences extend throughout the entire auditory pathway. Despite having significant residual hearing, children with mild to moderate sensorineural hearing loss (MMHL) experience deficits with general auditory processing, which puts them at risk of encountering language difficulties. Here, I will present two studies aimed at better understanding the neural consequence of partial degradation of the auditory input in children with MMHL. The first study examined the developmental effects of childhood MMHL on auditory discrimination of speech, “speech-like” and “nonspeech” stimuli, using the Mismatch Negativity (MMN). We tested 46 children with MMHL and 44 normally-hearing chronological age-matched controls (CA). Children were divided into two age groups: “younger” (8-11 years) and “older” (12-16 years). Our main result indicated that, while present in younger children with MMHL, there was no significant MMN in older MMHL children, whatever the condition. In an attempt to replicate this finding, fourteen children from the initial younger group participated in a longitudinal follow-up study again 6 years later (age range: 14-17 years). Although this group had a significant MMN when they were aged 7-11 years, this was only the case for speech when they reached 14-17 years. Our findings suggest that even mild or moderate levels of hearing loss during childhood may entail a persistent damage of auditory cortical functioning. A second study was conducted to evaluate the benefit of hearing aid amplification at various levels of the auditory pathway in children with MMHL. Preliminary results (n = 14 children with MMHL) suggest that, although simulated amplification normalizes speech processing at the subcortical level, it is not the case at the cortical level. Clinical implications of these two studies will be presented. Results will be discussed with respect to the existing literature on profoundly deaf children with cochlear implant and animal studies, which highlight long-term consequences of MMHL on the neural processing of sounds.
This research was supported by an Economic and Social Research Council (ESRC) First Grants Award (RES-061-25-0440) to LH and a European Union ITN grant (FP7-607139).