Ataxic dysarthria often refers to disturbance of coordinated articulatory movements in SCD subjects. In our recent study of acoustic analysis of selected speech samples obtained from normal and ataxic subjects, it was revealed that the ataxic speech diagnosed as having "scanning" was characterized by slower speaking rate, inconsistent segment duration of both vowels and consonants, and significant shortening of phonemically long Japanese vowels, as compared to the normal speech. The findings are apparently different from those reported in the study of ataxic speech characteristics of the subjects speaking Germanic languages. Thus, the impression of "scanning" in Japanese ataxic subjects derives mainly from the breakdown of isochrony in terms of difficulty in keeping the length of segments (morae) of Japanese invariable during speech production. The acoustic analysis of selected Japanese sentences is considered to be one of the appropriate methods for objective evaluation of ataxic symptoms.
