Objectives: The purpose of this investigation was to determine if adult bilateral cochlear implant
recipients could benefit from using a speech processing strategy in which the input
spectrum was interleaved among electrodes across the two implants.
Design: Two separate experiments were conducted. In both experiments, subjects were tested
using a control speech processing strategy and a strategy in which the full input
spectrum was filtered so that only the output of half of the filters was audible to
one implant, while the output of the alternative filters was audible to the other
implant. The filters were interleaved in a way that created alternate frequency “holes”
between the two cochlear implants.
Results: In experiment one, four subjects were tested on consonant recognition. Results indicated
that one of the four subjects performed better with the interleaved strategy, one
subject received a binaural advantage with the interleaved strategy that they did
not receive with the control strategy, and two subjects showed no decrement in performance
when using the interleaved strategy. In the second experiment, 11 subjects were tested
on word recognition, sentences in noise, and localization (it should be noted that
not all subjects participated in all tests). Results showed that for speech perception
testing one subject achieved significantly better scores with the interleaved strategy
on all tests, and seven subjects showed a significant improvement with the interleaved
strategy on at least one test. Only one subject showed a decrement in performance
on all speech perception tests with the interleaved strategy. Out of nine subjects,
one subject preferred the sound quality of the interleaved strategy. No one performed
better on localization with the interleaved strategy.
Conclusion: Data from this study indicate that some adult bilateral cochlear implant recipients
can benefit from using a speech processing strategy in which the input spectrum is
interleaved among electrodes across the two implants. It is possible that the subjects
in this study who showed a significant improvement with the interleaved strategy did
so because of less channel interaction; however, this hypothesis was not directly
tested.
Key Words Bilateral - cochlear implants - electrodes
