Auditory perception in early-deafened, late-implanted cochlear-implant users

Speech communication is crucial to social interactions, but deafness can
seriously hinder this. Cochlear implants (CIs) are prosthetic auditory devices
that restore hearing in severely hearing deprived and deaf individuals. They
are very successful in providing good speech perception in quiet, yet there
remain many unsolved auditory problems. These come mainly from the fact that
the sound signal delivered by the device is degraded compared to normal hearing
especially for pitch perception and speech perception in more complex listening
environments. The success and limitations of the device, namely are largely
known for traditional patients; individuals who became deaf early or late (
pre- or post-lingually deafened, i.e., before or after language acquisition,
respectively), and who received a CI in a relatively short period of time after
the deafness onset (Ba*kent et al. 2016).

This project is about a relatively new implantable group that constitutes an
understudied clinical population: the early-deafened, late-implanted (EDLI) CI
users. EDLI is defined as severe hearing loss at least since preschool (onset
six years of age or earlier), meaning deafness onset during language
acquisition, and implanted at sixteen years of age or later (Fuller et al.
2013; Mallinckrodt et al. (in preparation); Goorhuis-Brouwer et al 2000).
Clinics traditionally have not implanted this group, due to the potential
negative effects of auditory deprivation, but our own clinic at UMCG has a
special protocol developed for EDLI users. This gives the unique opportunity to
study this group which, combined with limited knowledge from previous
literature (Houston and Miyamoto 2010; Santarelli et al. 2008; De Raeve 2010;
Most, Shrem, and Duvdevani 2010; Yoshida et al. 2008), indicate potential
benefits of implantation. To fill in the gap in our knowledge on the
implantation outcome for EDLI, this study will systematically investigate the
perception of speech in quiet, noise or in concurrent speech and the perception
of pitch-related tasks, such as music, tasks that are known to be particularly
difficult for thenormal group of CI users.

Our expectation that the EDLI group may positively benefit from CI comes from a
small number of studies, due possibly to the very small size of this implantee
population worldwide. Despite a delay between the onset of deafness and the
implantation, which has negative consequences for the speech perception outcome
in general (Blamey et al. 2013), and a potential deficit in language skills due
to the onset of deafness during speech language development in early childhood,
a subgroup of EDLI CI users has been observed to benefit from implantation
regarding speech perception (Houston and Miyamoto 2010; Santarelli et al. 2008;
De Raeve 2010; Most, Shrem, and Duvdevani 2010; Yoshida et al. 2008).

Regarding other outcomes of implantation, our lab investigated the subjective
music perception and appreciation in post-lingually implanted and EDLI CI users
and the outcomes for health-related quality of life (QoL) (Fuller et al. 2013).
EDLI showed an improvement in quality of life after implantation (Mallinckrodt
et al. (in preparation)). A surprising finding was that the EDLI CI users, in
contrast to post-lingually deafened CI-users, find listening to music pleasant.
Also the quality of the sound of music was rated positively subjectively,
whereas post-lingually deafened CI users rated the quality negatively. There
are a number of potential explanations for the differences between these
groups: 1) EDLI might simply lack previous exposure to music with acoustical
hearing, and hence may appreciate music input, even if it is degraded in
quality, due to the lack of a reference for good quality. 2) Our clinical
protocol calls for implanting most promising candidates, and it is possible
that the protocol works effectively and is successful in maximizing
implantation outcome. Then we would expect our EDLI group to perform well in
speech and sound perception tasks. 3) EDLI group does not perform well for
sound perception, but they are still satisfied with their device as it still
provides some improvement in hearing. It is hence timely to find the
differences and the possible positive outcomes for both speech and music, to
give extra support for making an evidence-based decision on implant candidacy
of early-deafened individuals.

Our research will provide a better understanding of the effect of cochlear
implantation in this understudied group of CI users, the EDLI. Not only will we
learn more about the effect of the duration of deafness, the project might also
lead to new implantation programs for CI users. Lastly, the differences between
the three known groups of implantees give comprehensive insight in the
influence of for example a period of deafness on outcomes of implantation
and/or the plasticity of the human brain.

The objective of this study is to identify the perception of speech in quiet
and in noise or in speech, as well as sensitivity to pitch-related speech and
music-related stimuli, such as emotion identification, gender categorization
and melodic contour identification. Furthermore, subjectively the quality of
life, hearing ability and speech production will be tested.

Behavioural, case-control study. The participants listen to acoustic stimuli in
a sound-treated room and the perception is measured via percent correct scores
per test.

There are no known risks or benefits associated with the participation in the
experiment. There will be one session that last for about three hours. Adequate
breaks are built into the experiment and no food or drinks will be provided.