Range and Precision of Formant Movement in Pediatric Dysarthria

Abstract

Purpose: This study aimed to improve understanding of speech characteristics associated with dysarthria in children with cerebral palsy by analyzing segmental and global formant measures in single-word and sentence contexts.

Method: Ten 5-year-old children with cerebral palsy and dysarthria and 10 age-matched, typically developing children participated in this study. Vowel space area and second formant interquartile range were measured from children's elicited productions of single words and sentences.

Results: Results showed that the children with dysarthria had significantly smaller vowel space areas than typically developing children in both word and sentence contexts; however, overall ranges of second formant movement did not differ between groups in word or sentence contexts. Additional analysis of single words revealed that, compared to typical children, children with dysarthria had smaller second formant interquartile ranges in single words with phonetic contexts requiring large changes in vocal tract configuration, but not in single words with monophthongs.

Conclusions: Results of this study suggest that children with dysarthria may not have globally reduced ranges of articulatory movement compared to typically developing peers; however, they do exhibit reduced precision in producing phonetic targets.

Figure 1.

Differences between speech motor impaired (SMI) and typically developing (TD) groups on (a) acoustic vowel area in words and sentences, (b) second formant interquartile range (F2 IQR) in words and sentences, and (c) F2 IQR for single words with monophthongs and single words with large F2 transitions. Circles denote outliers.

Figure 2.

Vowel quadrilaterals for children in the speech motor impaired (SMI) and typically developing (TD) groups in (a) single words and (b) sentences. F1 = first formant; F2 = second formant.

Figure 3.

Example F2 trajectories from one child in the SMI group and one child in the TD group for (a) productions of a monophthong word (seat) and a large F2 transition word (toys), and (b) production of the sentence “Both faces are happy.”

Figure 4.

Scatterplots showing the correlation between overall intelligibility and acoustic variables for children in the SMI group. For each acoustic measure, red lines denote the average value of children in the TD group, and the shaded regions indicate 1 SD above and below the TD mean. Graphs show the relationship between overall intelligibility and (a) single-word vowel space, (b) sentence vowel space, (c) second formant interquartile range (F2 IQR) of large transition words, and (d) F2 IQR of sentences.