Speech Motor Control in Children with Downs Syndrome: Evidences from Formant Centralization Ratio

Abstract

Introduction : Studies have highlighted the sensitivity of Formant centralization ratio (FCR) in the identification of vowel centralization. Since children with Downs Syndrome (DS) are found to exhibit imprecise articulation, the present study aimed at evaluating whether children with DS exhibit vowel centralization using FCR. Method : The study included 30 children with Downs syndrome and 30 healthy age and gender matched controls in the age range of 6-8 years. Materials consisted of 9 words with three vowels (/i/, /u/, and /a/) in the initial, medial, and the final word positions respectively. First and second formant frequency values were extracted using PRAAT software. The vowel-formant data (e.g., frequency of F1, F2 etc.) were separately averaged for each child and then the FCR was constructed from these averages using the formula (F2u+F2a+F1i+F1u) / (F2i+F1a). Independent t-test was employed to find out the significance of difference between the means of the two groups. Results : The results of Independent t-test revealed significant difference between the mean FCR of both the groups at t= 8.535, p < 0.00 indicating higher FCR values in children with Downs syndrome in comparison to typically developing peers. Conclusion : The results of the present study indicated that FCR obtained from both the groups vary significantly, thereby indicating that the vowel production in children with Downs syndrome may be subjected to vowel centralization. The present findings suggest the potential abilities of FCR metric in identifying vowel errors without characterizing the nature of vowel abnormalities and hence this metric should be used in the clinical population with caution.