Objective and Methods:

This study examined the sensitivity of four cochlear implant (CI) listeners to ITD in different portions of four-pulse sequences in lateralization discrimination. ITD was present either in all the pulses (referred to as condition "Wave"), the two middle pulses (Ongoing), the first pulse (Onset), the last pulse (Offset), or both the first and last pulse (Gating). All ITD conditions were tested at different pulse rates (100, 200, 400, and 800 pulses per second, pps). Also, five normal hearing (NH) subjects were tested. The NH subjects listened to an acoustic simulation of CI stimulation.

Results:

All CI and NH listeners were sensitive in condition "Gating" at all pulse rates for which they showed sensitivity in condition "Wave". The sensitivity in condition "Onset" increased with the pulse rate for three CI listeners as well as for all NH listeners. The performance in condition "Ongoing" varied among the subjects. One CI listener showed sensitivity up to 800 pps, two up to 400 pps, and one at 100 pps only. The group of NH listeners showed sensitivity up to 200 pps.

Application:

CI listeners' ability to detect ITD from the middle pulses of short trains indicates fine timing relevance of stimulation pulses to lateralization. This is also relevant to CI stimulation strategies.

Funding:

Internal

Publications:

  • Laback, B., Majdak, P., Baumgartner, W. D. (2007). Lateralization discrimination of interaural time delays in four-pulse sequences in electric and acoustic hearing, J. Acoust. Soc. Am. 121, 2182-2191.
  • Laback, B., Majdak, P., Baumgartner., W.D. (2005). Interaural time differences in temporal fine structure, onset, and offset in bilateral electrical hearing, presented at the 28th Meeting of the Association for Research in Otolaryngology, New Orleans. 
  • Laback, B., Majdak, P., Baumgartner, W. D. (2006). Interaural Time Differences in Ongoing and Gating Signal Portions in Acoustic and Electric Hearing: Model Results, Proceedings of DAGA 2006, Braunschweig. 
  • Laback, B., Majdak, P., Baumgartner, W. D. (2005). Fine structure and gating interaural time differences in electrical and acoustical hearing: effects of stimulus duration, presented at the Conference on Implantable Auditory Prostheses (CIAP), Asilomar.
  • Laback, B., Majdak, P., Baumgartner., W.D. (2004). Sensitivity to interaural time differences in temporal fine-structure, onset, and offset in bilateral electrical hearing, presented at 5th Wullstein Symposium on Bilateral Cochlear Implants and Binaural Signal Processing, Würzburg.