Spectral measures of the effects of Friedreich's ataxia on speech

This study identifies two measures of the effects of Friedreich's ataxia (FRDA) on speech motor control. Speech samples of 17 healthy controls and 37 speakers with dysarthria associated with FRDA were recorded during one structured and one unstructured speaking task. Two measures of spectral variation were used that relate to the rate and range of changes that occur in the spectral envelope. Linear mixed models revealed significant effects of GROUP, TASK, and GROUP*TASK. FRDA speech samples had slower rate of spectral change and reduced spectral range. Healthy speakers produced faster rates of spectral change in read text compared to conversation, but speakers with dysarthria did not. The results suggest that structured speaking tasks which demand large spectral variation may be particularly useful in assessing the dysarthria. It is concluded that the rate of spectral change is a useful measure of dysarthria associated with FRDA.