Temporal masking in hearing with cochlear implants R.H. Pierzycki and B.U. Seeber MRC Institute of Hearing Research, Science Road, University Park, Nottingham, UK Normal hearing (NH) listeners are very good at detecting a signal in a brief gap between two maskers. There, masking from the preceding (forward, FWD) masker lasts longer than masking from the succeeding (backward, BWD) masker (Fastl, 1977). However, cochlear implant (CI) users struggle to detect signals in masker gaps, even though FWD masking in NH and CI hearing has been found to be similar (Shannon, 1990). We tested temporal masking from FWD, BWD and the combination of FWD and BWD maskers with CI users to investigate its impact on the ability of CI users to detect signals in the masker gaps. Detection thresholds of a 10 ms-long probe presented alone (threshold in quiet) or with 300 ms-long maskers were measured with seven adult CI users. The probe and maskers were constant-amplitude, constant-rate electric pulse trains and stimulated the auditory nerve via the mid-array electrode of the CI. Recovery from FWD and BWD masking functions were obtained from detection thresholds at masker/probe delays of 10 to 100 ms. For the combined FWD and BWD masker, recovery from masking functions were obtained from detection thresholds of the 10-ms probe placed symmetrically in 30 to 210 ms-long gaps between the combined maskers. Generally, probe thresholds decreased with the increase of the delay or the gap duration. However, the recovery from masking varied across subjects – from very little to full recovery at 100 ms delay. The recovery from BWD masking was slower than that observed in NH for all but one CI user, and was as slow as the recovery from FWD masking for several CI users. Recovery from masking from a combined FWD and BWD masker required gap durations longer than the delays needed for recovery from FWD masking. Our results suggest that the difficulties CI users experience when listening for a signal in masker gaps may be due to long recovery from both FWD and BWD masking and not from FWD masking alone as in NH. Acknowledgements Supported by the Intramural Programme of the Medical Research Council. References Fastl H. 1977. Temporal masking effects: II. Critical band noise masker. Acustica, 36, 317-331. Shannon R. 1990. Forward masking in patients with cochlear implants. J. Acoust. Soc. Am., 88, 741-744.