Language comprehension and sensorimotor learning with cochlear-implant simulated speech

Cochlear implants (CIs) are a device that can provide auditory input for individuals who are deaf, giving them access to spoken language. This experiment aimed to investigate whether typical hearing participants can learn to use CI simulated speech input for language comprehension and sensorimotor control of speech during production. The experiment was made up of two phases. First, a perceptual learning phase tested recognition of noise vocoded sentences before and after a training task which was manipulated between groups; either a perception training task where participants listened to noise vocoded sentences while reading matching text, or a production training task where participants read aloud sentences whilst hearing their own voice noise-vocoded in real-time. The second phase of the experiment tested sensorimotor learning with CI speech. Participants read aloud sentences while hearing their voice noise vocoded in real-time, with an additional perturbation to their formants (spectral properties of speech which determine the vowel sound). When speaking with non-vocoded feedback, speakers typically show corrective adjustments to their production of speech sounds in order to compensate for such formant perturbations; this is known as speech motor adaptation. Preliminary results with N = 20 (target N = 30) indicate that both the perception and production training tasks in the first phase resulted in significant improvements in recognition of noise vocoded sentences; training type however did not affect the magnitude of this improvement. For the second phase, no significant speech motor adaptation was found at the group level in response to the formant perturbations.