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Neural mechanisms underlying speech perception in children with speech sound disorders

Purpose: The underlying mechanisms of speech sound disorder (SSD) are unknown. To examine the relationship between inaccurate phonological representations and speech production ability, neural changes that occurred in conjunction with speech treatment were measured. Method: Twenty preschool-aged children with SSD participated in a traditional speech treatment program targeting a single sound (/ɹ l ʧ θ s k/) for 19 sessions. Event-related potential (ERP) recordings were completed before and after treatment, with approximately three months between sessions. During ERP recordings, two oddball stimulus sets, each containing four consonant-vowel (CV) syllables: one standard (ba/treated sound) and three deviants (ba/treated sound, da, one other CV) were presented. ERP responses indexing speech sound encoding (auditory P1/P2) and speech sound discrimination (mismatch negativity, MMN) were measured.Results: Children’s speech discrimination responses to treated sounds shifted from a positive mismatch response (PMR) pre-treatment to a MMN response post-treatment. Pre-treatment treated sound P1/P2 latencies negatively correlated with the amount of change in speech production accuracy.Conclusions: Children’s speech discrimination responses changed from using developmentally immature neural networks pre-treatment to using more mature networks after treatment, suggesting that children’s phonological representations of treated sounds became more fine-grained and/or detailed after treatment. Interestingly, children’s pre-treatment neural responses correlated with treatment outcomes, providing initial evidence for a biomarker of speech production ability.