Objective verification of continuous speech sound discrimination using the acoustic change complex.

Objective: To evaluate the feasibility of using the acoustic change complex (ACC) as an objective cortical marker of continuous speech sound discrimination using connected Ling-six stimuli. Design: Cortical auditory evoked potentials were recorded from 10 young adults with normal hearing using a continuous, pause-free sequence of the six Ling phonemes (/u-a-i-ʃ-s-m/). ACC responses were recorded in a passive listening paradigm with minimal electrodes. Reproducibility was assessed in a subset of participants retested 1 year later. Results: Robust ACC responses were elicited for all six phonemic transitions in every participant, indicating reliable cortical discrimination within the continuous speech stream. Although response morphology varied across listeners, within-subject responses demonstrated strong reproducibility over a one-year interval (mean cross-correlation = 0.95). Conclusion: Continuous Ling-six stimuli reliably evoke ACC responses reflecting cortical speech sound discrimination. This efficient and repeatable paradigm shows promise as an objective verification tool for auditory learning and sound discrimination, particularly in populations for whom behavioral assessment is unreliable.