Articulatory Perturbation Disrupts Sensorimotor Integration During Categorical Speech Perception

Growing evidence suggests that articulatory representations in the sensorimotor system contribute to speech perception, but their functional relevance remains unclear. Here, we investigated the impact of altered articulatory feedback on phonetic categorization and its neural correlates. Using magnetoencephalography (MEG), participants performed a vowel categorization task under a subtle lip perturbation. Classifiers trained to decode perceived phonetic categories from single-trial brain responses showed significantly reduced accuracy when tested on perturbed trials, indicating that sensorimotor representations support phonetic categorization in a state-dependent manner. Regions with highest contribution to decoding accuracy, including auditory and speech motor areas, showed the greatest perturbation-related disruption. Sensorimotor activity also revealed marked individual differences: participants clustered into two subgroups, one showing perceptual shifts congruent with the lip posture and the other showing opposite shifts. By linking neural activity patterns to perceptual outcomes, our findings demonstrate that articulatory representations engaged during speech perception contribute functionally to phonetic processing and help explain individual variability in sensitivity to articulatory inputs.