Auditory-perceptual training using a simulation of a cochlear-implant system: A controlled study

This experiment investigated the effectiveness of lexical training to improve the ability of 32 normally-hearing subjects to understand speech that had been processed by a simulation of a cochlear-implant system. Signals were vocoded and spectrally shifted to simulate the consequences of a 3mm tonotopic misalignment between frequency and place of stimulation in the cochlea. The training task was a 2alternative forced-choice procedure. On each trial, subjects chose which of two words displayed orthographically on a computer screen matched a target word. The effectiveness of ‘High-Variability’ auditory training, in which training words were recorded by ten different talkers, was compared with ‘Single-Talker’ auditory training. The control task was a visual analogue of the auditory training task. Auditory training was more effective than control training: control training produced an improvement of 4.1% (95% c.i. 2.0-6.2%), in the ability to identify words in sentences, while auditory training produced an improvement of 9.4% (95% c.i. 7.4-11.4%). There was a trend for High-Variability auditory training to be associated with greater improvements (mean improvement 11.5%, 95% c.i. 9.2-13.9%) than Single-Talker auditory training (mean improvement 7.2%, 95% c.i. 4.9-9.6%). In addition, auditory training was associated with improved consonant recognition, but no change in vowel recognition. Hence, computer-based lexical training can improve the ability to recognise spectrallydistorted speech, and might therefore prove valuable to cochlear-implant users.