Psychophysical hearing tests of a new sound coding strategy for cochlear implant users

Cochlear implantation is the primary treatment for bilateral severe hearing
loss or deafness. A cochlear implant provides hearing through direct electrical
stimulation of the cochlear nerve. There are over 1800 cochlear implant users
in the Netherlands. Although their speech perception in quiet situations is
reasonable, pitch perception, music appreciation, intonation recognition as
well as voice recognition are still poor. Multiple reasons presumably
contribute to this poor performance. One of the reasons is that it is unlikely
that only around 20 electrodes in the watery perilymph in the inner ear fully
take over the functionality of around 13,000 finely tuned normally-functioning
sensory hair cells. Another reason are the limitations of the current sound
processings strategy of cochlear implants. Whereas normal hearing uses
tonotopic as well as temporal cues for the determination of pitch, most
cochlear implants provide only the tonotopic cues. The electrical stimulation
patterns provided by the implant do not contain fine-structured temporal
information.

The objective of the study is to answer the following questions:
a) Does the PLS-strategy improve pitch- and speech-perception?
b) How does the number of harmonics in consecutive channels influence frequency
discrimination, in speech coding strategies HiRes and PLS?

Psychophysical hearing tests, intraparticipant comparison, evaluation after 10
participants.

Psychophysical experiments: Loudness scaling test; frequency discrimination
test; speech perception test (in silence and noise).

The participants will spend a total of 10 hours (distributed over 2 visits)
performing the following psychophysical experiments: Loudness scaling test;
pitch discrimination test; speech recognition test.
The burden is that participants may find the experiments difficult and tiring.
There are no known risks associated with the experiments.
The benefit for the patient group as a whole is that if the PLS-strategy proves
useful, it can be applied in software upgrades of their regular sound
processor. It may resolve one of the primary complaints of current implant
users: poor speech perception in noise. Furthermore, knowledge about pitch
perception using temporal cues will help the field to develop better
strategies. There is no immediate benefit for the individual test subject.