Listening Effort with Bimodal Hearing versus Cochlear Implant alone

A Cochlear Implant (CI) allows profoundly deaf people to hear again by
translating acoustical signals to electrical signals, which it passes on to the
auditory nerve via electrodes in the cochlea. Listeners with state of the art
cochlear implants achieve very good speech recognition results. However, in
terms of listening effort there is still room for improvement. We hypothesize
that a good way of reducing listening effort is combining both conventional
hearing aids (HA) and cochlear implants (bimodal stimulation). The traditional
listening tests are not sufficiently sensitive to reflect listening effort, and
therefore a new method needs to be developed. The current study will first
evaluate the dual task paradigm as a suitable method for measuring listening
effort. Then we will look at differences in listening effort for CI alone vs
Bilateral listening.

Our first objective is two-fold; part of it is to evaluate the suitability of
the dual task paradigm as a measure for listening effort in a series of
simulation experiments. We will compare a linguistic and a non linguistic
secondary task in this context. The other part is to identify the conditions
for which the effect size is expected to be largest in real cochlear implant
users through these simulation experiments.
Our second objective is to see if there is any benefit of bimodal stimulation,
a.k.a combined acoustic and electric stimulation, for CI users in terms of
listening effort.

Within subject comparison of performance on dual task experiments for:
- normal hearing participants simulated single CI * different nrs of channels
vs unprocessed sound (regular hearing)
- normal hearing participants simulated bimodal hearing (HA + CI) vs single CI
- CI using participants - different nrs of channels
- CI using participants bimodal hearing (HA + CI) vs single CI

Subjects participate in a listening experiment combined with a secondary task.
They are instructed to focus primarily on the listening task, and difference in
performance on the secondary task - compared performance to the secondary task
alone - is recorded as a measure of listening effort associated with the
primary task. Additionally, the subjective mental taskload will be measured for
each condition, using the Dutch version of the NASA Task Load Index (NASA TLX).

In phase 3 of the study, with CI users, an additional task will be performed. A
simple response-time task that combines measures of speech understanding and
response-time in one task.

There are no known risks, nor benefits associated with participation.
The test session lasts for approximately 3 hours (including breaks) and
requires the continuous attention of the subject. This may be fatiguing.

Phase 3 experiment 1 requires participants to come to the UMCG twice, once for
1 hour, and once for 2 hours, and train for 1 hour a day at home between
visits. This may be considered an inconvenience.