Preliminary data indicate that the closed-set MCI task is a viable approach toward quantifying an important component of cochlear implant users' music perception. The improvement in MCI performance and generalization to FMI performance with training suggests that MCI training may be useful for improving cochlear implant users' music perception and appreciation; such training may be necessary to properly evaluate patient performance, as acute measures may underestimate the amount of musical information transmitted by the cochlear implant device and received by cochlear implant listeners.

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The present study investigated the relative importance of temporal and spectral cues in voice gender discrimination and vowel recognition by normalhearing subjects listening to an acoustic simulation of cochlear implant speech processing and by cochlear implant users. In the simulation, the number of speech processing channels ranged from 4 to 32, thereby varying the spectral resolution; the cutoff frequencies of the channels' envelope filters ranged from 20 to 320 Hz, thereby manipulating the available temporal cues. For normal-hearing subjects, results showed that both voice gender discrimination and vowel recognition scores improved as the number of spectral channels was increased. When only 4 spectral channels were available, voice gender discrimination significantly improved as the envelope filter cutoff frequency was increased from 20 to 320 Hz. For all spectral conditions, increasing the amount of temporal information had no significant effect on vowel recognition. Both voice gender discrimination and vowel recognition scores were highly variable among implant users. The performance of cochlear implant listeners was similar to that of normal-hearing subjects listening to comparable speech processing (4-8 spectral channels). The results suggest that both spectral and temporal cues contribute to voice gender discrimination and that temporal cues are especially important for cochlear implant users to identify the voice gender when there is reduced spectral resolution.

Learning electrically stimulated speech patterns can be a new and difficult experience for cochlear implant (CI) recipients. Recent studies have shown that most implant recipients at least partially adapt to these new patterns via passive, daily-listening experiences. Gradually introducing a speech processor parameter (eg, the degree of spectral mismatch) may provide for more complete and less stressful adaptation. Although the implant device restores hearing sensation and the continued use of the implant provides some degree of adaptation, active auditory rehabilitation may be necessary to maximize the benefit of implantation for CI recipients. Currently, there are scant resources for auditory rehabilitation for adult, postlingually deafened CI recipients. We recently developed a computer-assisted speech-training program to provide the means to conduct auditory rehabilitation at home. The training software targets important acoustic contrasts among speech stimuli, provides auditory and visual feedback, and incorporates progressive training techniques, thereby maintaining recipients' interest during the auditory training exercises. Our recent studies demonstrate the effectiveness of targeted auditory training in improving CI recipients' speech and music perception. Provided with an inexpensive and effective auditory training program, CI recipients may find the motivation and momentum to get the most from the implant device.

In cochlear implant (CI) patients, temporal processing is often poorest at low listening levels, making perception difficult for low-amplitude temporal cues that are important for consonant recognition and/or speech perception in noise. It remains unclear how speech processor parameters such as stimulation rate and stimulation mode may affect temporal processing, especially at low listening levels. The present study investigated the effects of these parameters on modulation detection by six CI users. Modulation detection thresholds (MDTs) were measured as functions of stimulation rate, mode, and level. Results show that for all stimulation rate and mode conditions, modulation sensitivity was poorest at quiet listening levels, consistent with results from previous studies. MDTs were better with the lower stimulation rate, especially for quiet-to-medium listening levels. Stimulation mode had no significant effect on MDTs. These results suggest that, although high stimulation rates may better encode temporal information and widen the electrode dynamic range, CI patients may not be able to access these enhanced temporal cues, especially at the lower portions of the dynamic range. Lower stimulation rates may provide better recognition of weak acoustic envelope information.

The present study explored the relative contributions of spectral and temporal information to voice gender identification by cochlear implant users and normal-hearing subjects. Cochlear implant listeners were tested using their everyday speech processors, while normal-hearing subjects were tested under speech processing conditions that simulated various degrees of spectral resolution, temporal resolution, and spectral mismatch. Voice gender identification was tested for two talker sets. In Talker Set 1, the mean fundamental frequency values of the male and female talkers differed by 100 Hz while in Talker Set 2, the mean values differed by 10 Hz. Cochlear implant listeners achieved higher levels of performance with Talker Set 1, while performance was significantly reduced for Talker Set 2. For normal-hearing listeners, performance was significantly affected by the spectral resolution, for both Talker Sets. With matched speech, temporal cues contributed to voice gender identification only for Talker Set 1 while spectral mismatch significantly reduced performance for both Talker Sets. The performance of cochlear implant listeners was similar to that of normal-hearing subjects listening to 4-8 spectral channels. The results suggest that, because of the reduced spectral resolution, cochlear implant patients may attend strongly to periodicity cues to distinguish voice gender.

After implantation, postlingually deafened cochlear implant (CI) patients must adapt to both spectrally reduced and spectrally shifted speech, due to the limited number of electrodes and the limited length of the electrode array. This adaptation generally occurs during the first three to six months of implant use and may continue for many years. To see whether moderate speech training can accelerate this learning process, 16 naïve, normal-hearing listeners were trained with spectrally shifted speech via an eightchannel acoustic simulation of CI speech processing. Baseline vowel and consonant recognition was measured for both spectrally shifted and unshifted speech. Short daily training sessions were conducted over five consecutive days, using four different protocols. For the test-only protocol, no improvement was seen over the five-day period. Similarly, sentence training provided little benefit for vowel recognition. However, after five days of targeted phoneme training, subjects' recognition of spectrally shifted vowels significantly improved in most subjects. This improvement did not generalize to the spectrally unshifted vowel and consonant tokens, suggesting that subjects adapted to the specific spectral shift, rather than to the eightchannel processing ingeneral. Interestingly, significant improvement was also observed for the recognition of spectrally shifted consonants. The largest improvement was observed with targeted vowel contrast training, which did not include any explicit consonant training. These results suggest that targeted phoneme training can accelerate adaptation to spectrally shifted speech. Given these results with normalhearing listeners, auditory rehabilitation tools that provide targeted phoneme training may be effective in improving the speech recognition performance of adult CI users.

The goal of the present study was to investigate the time course of adaptation by experienced cochlear implant users to a shifted frequency-to-electrode assignment in their speech processors. Speech recognition performance of three Nucleus-22 cochlear implant users was measured over a 3-month period, during which the implant listeners continuously wore "experimental" speech processors that were purposely shifted by 2-4 mm in terms of the frequency-to-electrode assignment relative to their normal processor. Baseline speech performance was measured with each subject's clinically assigned speech processor just prior to implementation of the experimental processor. Baseline speech performance was measured again after the 3-month test period, immediately following the reinstallation of the clinically assigned processor settings. Speech performance with the experimental processor was measured four times during the first week, and weekly thereafter over the 3-month period. Results showed that the experimental processor produced significantly lower performance on all measures of speech recognition immediately following implementation. Over the 3-month test period, consonant and HINT sentence recognition with the experimental processors gradually approached a performance level comparable to but still significantly below the baseline and postexperiment measures made with the clinically assigned processor. However, vowel and TIMIT sentence recognition with the experimental processors remained far below the level of the baseline measures even at the end of the 3-month experimental period. There was no significant change in performance with the clinically assigned processor before or after fitting with the experimental processor. The results suggest that a long-time exposure to a new pattern of stimulation may not be able to compensate for the deficit in performance caused by a 2-4-mm shift in the tonotopic location of stimulation, at least within a 3-month period.