Speech sensorimotor adaptation in young adult cochlear implant users with early implantation

Precise speech production depends on fine motor control minimizing errors in the produced sound. This control process can be disrupted when sensory signals are degraded, such as in auditory deprivation. In this case, cochlear implants (CIs) may improve speech production and perception provided that implantation is sufficiently early and extensive. The present study examined whether CI profiles influence speech sensorimotor adaptation by using a laboratory-based paradigm with altered auditory feedback. Participants included young-adult French native speakers (18-35 years), with hearing loss (HL) and early (<10 years old), long-term (>15 years) CI experience (HL-eCI). For comparison, we also tested HL individuals with different CI profiles (no or limited and late CI experience, HL-Other), normal-hearing controls (NH-C), and normal-hearing participants tested with a CI simulator (NH-simCI). Participants repeatedly produced the vowel /ø/ in the French word "deux", and the second formant (F2) was gradually increased over 50 trials to shift the vowel toward /e/, followed by 50 trials with the maximum perturbation. In the NH-simCI group, altered speech was presented through a six-band sine-vocoded CI simulator. The HL-eCI group showed clear adaptation in F2 comparable to the NH-C group, indicating that CIs can support the detection of auditory errors necessary for sensorimotor adaptation. In contrast, adaptation was limited in both the HL-Other and NH-simCI groups, suggesting that degraded auditory feedback restricts the effective use of auditory error signals. These results suggest that the effective use of CI feedback reflects substantial neural plasticity, shaped by early implantation and long-term auditory experience.