Declination and Segmentation in Children with Childhood Apraxia of Speech

Childhood apraxia of speech (CAS) is characterized by atypical timing between segments, leading to prosodic disruption at the lexical level. This study tested whether prosodic impairment in CAS extends to the intonational level by examining declination of fundamental frequency (f0). Eleven children with CAS and ten typically developing (TD) peers aged 5 to 11 years old produced real and nonce multisyllabic words embedded in carrier phrases. Acoustic measures of inter-segment duration (within-word, between-word) and average f0 across segments were extracted. Children with CAS exhibited significantly longer inter-segment durations both within and between words, influenced by lexical stress position (first syllable, second syllable) and word status (real, nonce). They also showed shallower f0 declination slopes than TD peers, indicating reduced overall pitch fall. Segmentation and declination were not significantly correlated, suggesting distinct mechanisms underlying timing and pitch organization. Consistent with prior work, segmentation was greatest for nonce words with non-initial stress. Reduced declination in CAS may reflect limitations in prosodic planning or programming at the intonational level. These findings highlight dissociable disruptions in timing and pitch patterning in CAS, contributing to a more comprehensive understanding of prosodic control in motor speech disorders.