When Hearing Is Tricky: Speech Processing Strategies in Prelingually Deafened Children and Adolescents with Cochlear Implants Having Good and Poor Speech Performance

Abstract

Cochlear implants provide individuals who are deaf with access to speech. Although substantial advancements have been made by novel technologies, there still is high variability in language development during childhood, depending on adaptation and neural plasticity. These factors have often been investigated in the auditory domain, with the mismatch negativity as an index for sensory and phonological processing. Several studies have demonstrated that the MMN is an electrophysiological correlate for hearing improvement with cochlear implants. In this study, two groups of cochlear implant users, both with very good basic hearing abilities but with non-overlapping speech performance (very good or very poor speech performance), were matched according to device experience and age at implantation. We tested the perception of phonemes in the context of specific other phonemes from which they were very hard to discriminate (e.g., the vowels in /bu/ vs. /bo/). The most difficult pair was individually determined for each participant. Using behavioral measures, both cochlear implants groups performed worse than matched controls, and the good performers performed better than the poor performers. Cochlear implant groups and controls did not differ during time intervals typically used for the mismatch negativity, but earlier: source analyses revealed increased activity in the region of the right supramarginal gyrus (220–260 ms) in good performers. Poor performers showed increased activity in the left occipital cortex (220–290 ms), which may be an index for cross-modal perception. The time course and the neural generators differ from data from our earlier studies, in which the same phonemes were assessed in an easy-to-discriminate context. The results demonstrate that the groups used different language processing strategies, depending on the success of language development and the particular language context. Overall, our data emphasize the role of neural plasticity and use of adaptive strategies for successful language development with cochlear implants.

The development of cortical processing of speech differs between children with cochlear implants and normal hearing and changes with parental singing

“…Instead, in the time window for the MMN, most responses in the CI groups were not significant, the significant but positive response in the CI preschoolers to the intensity decrement at T1 being the only exception. The positivity of this response in the CI preschoolers in the time window of the MMN is consistent with the previous findings by Ortmann et al (2013a , 2017) , Torppa et al (2014a , 2018) , and Engström et al (2020) . One possible reason for the lack of significant responses to the intensity increments in the CI group is the activation of the automatic gain control (ACG) of the CI device ( Stöbich et al, 1999 ).…”

The CI MuMuFe – A New MMN Paradigm for Measuring Music Discrimination in Electric Hearing

“…It is also important to point out that MMN and behavioral testing performance often fail to correspond in a strict one-to-one fashion; strong MMNs are not necessarily associated with higher scores (Bishop and Hardiman, 2010;Ortmann et al, 2017). This is also indicated in this study by the lack of significant correlations between MMN amplitudes and hit rates, which thus lends further support to the notion that a group difference at the behavioral level may not necessarily correspond to a group difference at the neurophysiological level.…”

The MMN as a viable and objective marker of auditory development in CI users

“…N ¼ number; ISI ¼ interstimulus interval: SOA ¼ stimulus onset asynchrony; 1)Within-block MMN ¼ the difference wave resulting from contrasting deviant stimuli within one block; across-block MMN ¼ the difference wave resulting from contrasting the deviant stimulus of one block with its physically identical counterpart of the another block where it is presented as a standard stimulus. Not reported in the Table: Petersen et al, 2015 (see Table 3); Ponton and Eggermont, 2001;Titterington et al, 2003;Torppa et al, 2012 (see Table 3); Torppa et al, 2014b (See Table 3 Ortmann et al, 2013Ortmann et al, , 2017. It is not yet clear which method is the best one even for NH subjects.…”