Acoustic Temporal Modulation Detection in Normal-Hearing and Cochlear Implanted Listeners: Effects of Hearing Mechanism and Development

Abstract

Temporal modulation detection ability matures over many years after birth and may be particularly sensitive to experience during this period. Profound hearing loss during early childhood might result in greater perceptual deficits than a similar loss beginning in adulthood. We tested this idea by measuring performance in temporal modulation detection in profoundly deaf children and adults fitted with cochlear implants (CIs). At least two independent variables could constrain temporal modulation detection performance in children with CIs: altered encoding of modulation information due to the CIauditory nerve interface, and atypical development of central processing of sound information provided by CIs. The effect of altered encoding was investigated by testing subjects with one of two different hearing mechanisms (normal hearing vs. CI) and the effect of atypical development was studied by testing two different age groups. All subjects were tested for their ability to detect acoustic temporal modulations of sound amplitude. A comparison of the slope, or cutoff frequency, of the temporal modulation transfer functions (TMTFs) among the four subject groups revealed that temporal resolution was mainly constrained by hearing mechanism: normal-hearing listeners could detect smaller amplitude modulations at high modulation frequencies than CI users. In contrast, a comparison of the height of the TMTFs revealed a significant interaction between hearing mechanism and age group on overall sensitivity to temporal modulation: sensitivity was significantly poorer in children with CIs, relative to the other three groups. Results suggest that there is an agespecific vulnerability of intensity discrimination or non-sensory factors, which subsequently affects sensitivity to temporal modulation in prelingually deaf children who use CIs.

Effects of age and hearing mechanism on spectral resolution in normal hearing and cochlear-implanted listeners

“…sensitivity to broadband intensity modulation develops more slowly in pre-lingually deaf CI users than in NH listeners (Park et al, 2015). The inconsistency between the present findings and the work of Park et al has several possible explanations.…”

“…These results were not expected, but in retrospect, are consistent with the reduced dynamic range of electric versus acoustic hearing. However, Park et al (2015) found no significant relationship between electrical dynamic range of their participants' clinical maps and amplitude modulation sensitivity. Given that patients were using their clinical processors and preferred settings, the relative influence of neural intensity coding and signal processing/compression on this effect cannot be determined in the present study.…”

“…Second, we predicted that across-channel intensity resolution would be affected by age in the CI group but not in the NH group. Immature across-channel intensity resolution was predicted based on a previous study that demonstrated slower development of intensity modulation detection in pre-lingually deaf CI users compared to NH listeners (Park et al, 2015). Third, we predicted that frequency resolution would correlate more strongly than across-channel intensity resolution with speech perception in CI users.…”

Cortical Activation Patterns Correlate with Speech Understanding After Cochlear Implantation

“…There are many factors that are known to affect performance when hearing through a cochlear implant, for example age correlates both with acoustical hearing abilities as well as with central processing abilities (Gates and Mills 2005; Humes et al 2012; Jin et al 2014; Park et al 2015). Although there was significant overlap between the ages of the participants in the implanted and normal-hearing cohorts ( Table 1 ), their mean ages were different (Mann-Whitney U-test, p<0.01).…”

Age-Related Performance on Vowel Identification and the Spectral-temporally Modulated Ripple Test in Children With Normal Hearing and With Cochlear Implants

“…While the authors did not specifically discuss the age at which SMRT performance peaked in hearing-impaired children, a possible interpretation of this observation is that decreased access to auditory information, and the degraded auditory signal that the central auditory system receives because of hearing loss, prolongs the maturation of spectral resolving capabilities. Other prior studies with pediatric CI users have demonstrated immature temporal sensitivity ( Jung et al., 2012 ) and intensity resolution ( Park, Won, Horn, & Rubinstein, 2015 ) in school-age children and adolescents compared with adults with CIs.…”