Spectral and temporal processing by prelingually deafened CI users.

This study investigates the spectral and temporal processing of a specific group of CI users: the prelingually deafened. In part 1A we will determine the electrode discrimination abilities of a group of prelingually deafened CI users. In part 1B we will use this information to create a new speech programme with less electrodes, and evaluate this programme objectively and subjectively. Part 2 focusses on the temporal procesing skills of these prelingually deafened CI users and looks into the corelation between temporal processing skills and speech understanding (part 2B).

Prelingually deafened cochlear implant users mostly do not achieve a high level of speech understanding with their cochlear implant (CI). We hypothesize that the information these patients are getting from their CI is often too complex for them to process, given their compromised auditory processing abilities due to the long duration of deafness. A simplified auditory signal, containing only discriminable spectral channels, might improve speech understanding with the CI specifically for this group of patients. Also, the influence of the longterm deafness on temporal processing abilities and whether temporal processing skills are related to speech understanding performance with the CI, is yet unknown. More knowledge on these topics is important for the development and adjustment of speech processing strategies for this group of patients.



Objectives:

To determine the electrode discrimination abilities of prelingually deafened CI users (part 1A) and to adjust the speech processing strategy based on these possibilities, in order to improve auditory speech understanding with the cochlear implant (part 1B). Furthermore, we want to determine the
temporal resolution capacities of prelingually deafened CI users, obtain
reference values in postlingually deafened CI users measured under the
same testing conditions (part 2A) and investigate the correlation
between temporal resolution and speech understanding (part 2B).

Part 1A: Electrode discrimination measured with an adaptive listening task, expressed as the minimal distance (either in basal or apical direction) between two electrodes that is needed for the subject to perceptually distinguish both electrodes in 70,7% of cases. This part of the study ends when all testing procedures are terminated (3 visits).

Part 1B: Speech understanding with both programmes is measured on the NVA monosyllabic word list (phoneme score in %), the number of words correct per minute on the speech tracking test and the prosody- and wordscore in % on the Erber test. This part of the study has a fixed time frame of 4 weeks, with 3 visits. The third visit is the endpoint.

Part 2A: The modulation detection thresholds are measured with an adaptive procedure. They are the minimal modulation depth that is needed for the subject to be able to perceptually distinguish between an amplitude modulated noise sample and an unmodulated noise sample, and a measure of temporal resolution. This part of the study ends after termination of the test procedure and speech testing (2 visits). Speech tests are the same as in part 1B.

An intervention is only done in part 1B of the study. Parts 1A, 2A and 2B are observational cohort studies. The intervention in part 1B consists of an adaptation in the listening programme the subject uses with his cochlear implant, thus a change in the setting of the medical device that the subject already uses. The new programme is made with the standard clinical fitting software. This new programme is based on the results for the individual subject of part 1A and will comprise the switching off of non-discriminable electrodes. A comparison is made between this new programme (in terms of subjective preference and objective speech understanding sores) and the standard clinical programme that the subject has used until then.