Current cochlear implants (CIs) are very successful in restoring speech understanding in individuals with profound or complete hearing loss by electrically stimulating the auditory nerve. However, the ability of CI users to localize sound sources and to understand speech in complex listening situations, e.g. with interfering speakers, is dramatically reduced as compared to normal (acoustically) hearing listeners. From acoustic hearing studies it is known that interaural time difference (ITD) cues are essential for sound localization and speech understanding in noise. Users of current bilateral CI systems are, however, rather limited in their ability to perceive salient ITDs cues. One particular problem is that their ITD sensitivity is especially low when stimulating at relatively high pulses rates which are required for proper encoding of speech signals.
In this project we combine psychophysical studies in human bilaterally implanted listeners and physiological studies in bilaterally implanted animals to find ways in order to improve ITD sensitivity in electric hearing. We build on the previous finding that ITD sensitivity can be enhanced by introducing temporal jitter (Laback and Majdak, 2008) or short inter-pulse intervals (Hancock et al., 2012) in high-rate pulse sequences. Physiological experiments, performed at the Eaton-Peabody Laboratories Neural Coding Group (Massachusetts Eye and Ear Infirmary, Harvard Medical School, PI: Bertrand Delgutte), are combined with matched psychoacoustic experiments, performed at the EAP group of ARI (PI: Bernhard Laback). The main project milestones are the following: