Adaptation to the acoustic world following cochlear implantation does not typically include formal training or extensive audiological rehabilitation. Can cochlear implant (CI) users benefit from formal training, and if so, what type of training is best? This study used a pre-/posttest design to evaluate the efficacy of training and generalization of perceptual learning in normal hearing subjects listening to CI simulations (eight-channel sinewave vocoder). Five groups of subjects were trained on words (simple/complex), sentences (meaningful/anomalous), or environmental sounds, and then were tested using an open-set identification task. Subjects were trained on only one set of materials but were tested on all stimuli. All groups showed significant improvement due to training, which successfully generalized to some, but not all stimulus materials. For easier tasks, all types of training generalized equally well. For more difficult tasks, training specificity was observed. Training on speech did not generalize to the recognition of environmental sounds; however, explicit training on environmental sounds successfully generalized to speech. These data demonstrate that the perceptual learning of degraded speech is highly context dependent and the type of training and the specific stimulus materials that a subject experiences during perceptual learning has a substantial impact on generalization to new materials.

A listener's ability to utilize indexical information in the speech signal can enhance their performance on a variety of speech perception tasks. It is unclear, however, whether such information plays a similar role for spectrally reduced speech signals, such as those experienced by individuals with cochlear implants. The present study compared the effects of training on linguistic and indexical tasks when adapting to cochlear implant simulations. Listening to sentences processed with an eight-channel sinewave vocoder, three separate groups of subjects were trained on a transcription task ͑transcription͒, a talker identification task ͑talker ID͒, or a gender identification task ͑gender ID͒. Pre-to posttest comparisons demonstrated that training produced significant improvement for all groups. Moreover, subjects from the talker ID and transcription training groups performed similarly at posttest and generalization, and significantly better than the subjects from the gender ID training group. These results suggest that training on an indexical task that requires high levels of controlled attention can provide equivalent benefits to training on a linguistic task. When listeners selectively focus their attention on the extralinguistic information in the speech signal, they still extract linguistic information, the degree to which they do so, however, appears to be task dependent.

The effect of feedback and materials on perceptual learning was examined in normal hearing listeners exposed to cochlear implant simulations. Generalization was most robust when feedback paired the spectrally degraded sentences with their written transcriptions, promoting mapping between the degraded signal and its acoustic-phonetic representation. Transfer appropriate processing theory suggests that such feedback was most successful because the original learning conditions were reinstated at testing: performance was facilitated when both training and testing contained degraded stimuli. In addition, the effect of semantic context on generalization was assessed by training listeners on meaningful or anomalous sentences. Training with anomalous sentences was as effective as with meaningful sentences, suggesting that listeners were encouraged to use acoustic-phonetic information to identify speech than to make predictions from semantic context.

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