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Electrode Selection and Speech Understanding in Patients With Auditory Brainstem Implants

McKay, Colette M.1,2; Azadpour, Mahan1,3; Jayewardene-Aston, Deanne1,4; O’Driscoll, Martin1,4; El-Deredy, Wael1

doi: 10.1097/AUD.0000000000000146
Research Articles
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Objectives: The objective of this study was to evaluate whether speech understanding in auditory brainstem implant (ABI) users who have a tumor pathology could be improved by the selection of a subset of electrodes that were appropriately pitch ranked and distinguishable. It was hypothesized that disordered pitch or spectral percepts and channel interactions may contribute significantly to the poor outcomes in most ABI users.

Design: A single-subject design was used with five participants. Pitch ranking information for all electrodes in the patients’ clinic maps was obtained using a pitch ranking task and previous pitch ranking information from clinic sessions. A multidimensional scaling task was used to evaluate the stimulus space evoked by stimuli on the same set of electrodes. From this information, a subset of four to six electrodes was chosen and a new map was created, using just this subset, that the subjects took home for 1 month’s experience. Closed-set consonant and vowel perception and sentences in quiet were tested at three sessions: with the clinic map before the test map was given, after 1 month with the test map, and after an additional 2 weeks with their clinic map.

Results: The results of the pitch ranking and multidimensional scaling procedures confirmed that the ABI users did not have a well-ordered set of percepts related to electrode position, thus supporting the proposal that difficulty in processing of spectral information may contribute to poor speech understanding. However, none of the subjects benefited from a map that reduced the stimulation electrode set to a smaller number of electrodes that were well ordered in place pitch.

Conclusions: Although poor spectral processing may contribute to poor understanding in ABI users, it is not likely to be the sole contributor to poor outcomes.

Patients who use auditory brainstem implants participated in a study to test the hypothesis that use of a small number of channels that are highly distinct and appropriately pitch ranked would lead to improved speech understanding. Although patients varied in their perception of spectral channels, the hypothesis was not supported.

1School of Psychological Sciences, The University of Manchester, Manchester, United Kingdom; 2The Bionics Institute of Australia, Melbourne, Victoria, Australia; 3School of Medicine, New York University, New York, New York, USA; and 4Manchester Auditory Implant Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom.

The work was supported by Cochlear UK with a grant to the first author and a PhD studentship to the third author.

The authors declare no conflict of interest.

Received April 25, 2013; accepted December 27, 2014.

Address for correspondence: Colette M. McKay, The Bionics Institute of Australia, 384-388 Albert Street, East Melbourne, Victoria 3002, Australia. E-mail: cmckay@bionicsisntitute.org

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