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Investigating Perceptual Subgroups in Speakers With Ataxic Dysarthria: An Auditory Free Classification Approach.

PURPOSE
Ataxic dysarthria has presented with considerable heterogeneity in the presentation of speech characteristics. Converging evidence supports the existence of subgroups, specifically related to the instability and inflexibility of motor patterns as a possible explanation of this variability.


METHOD
To further examine the alignment of the speech characteristics of ataxic dysarthria with the instability/inflexibility framework, 23 graduate student listeners participated in an auditory free classification task and a guided classification task. Listeners grouped 15 speakers with ataxic dysarthria based on their judgment of the most salient perceptual characteristics during two speaking tasks: alternating motion rates (AMRs) and connected speech (one to two sentences). Listener ratings were then compared with a priori determinations of speakers who fit the instability subgroup profile and the inflexibility subgroup profile.


RESULTS
Results of both the free classification and guided classification listening paradigms provided supportive evidence of subgroups, particularly for the AMR task, in the context of strong inter- and intrarater reliability.


CONCLUSION
This study adds to the growing evidence of the existence of instability and inflexibility subgroups in ataxic dysarthria and serves as a proof of concept for use of the auditory free classification paradigm in dysarthria subgroup research.