M. Helen Southwood
Dept. of Biocommun., Univ. of Alabama at Birmingham, UAB Station VH 503, Birmingham, AL 35294
Diadochokinesis (DDK), the rapid production of syllable sequences, is used when assessing motor speech disorders. The validity and reliability of DDK tasks has been questioned because of the variability in performance across and within speakers. The variability in the temporal and spectral characteristics of ten syllables extracted from the middle of the DDK utterances /pu/ and /ti/ produced by one normal and four ALS subjects was examined. Smaller coefficients of variation for the durations of /(inverted vee)/ (0.10--0.20) and /i/ (0.05--0.13) were observed for the ALS speakers. The coefficient for the duration of /p/ tended to be slightly higher for the ALS speakers (0.22--0.38), regardless of the severity of the speech impairment. Smaller coefficients of variation were observed for the mildly and severely dysarthric speakers for /t/, 0.11 and 0.12, respectively. Skewness and kurtosis measures were also computed. Evaluation of the averaged spectrum for both /(inverted vee)/ and /i/ revealed similar patterns across repetitions for each speaker, although minor variations were observed across the speakers. The findings suggest that ALS speakers consistently produce temporal and spectral characteristics of syllables in DDK sequences.