Investigating Perceptual Subgroups in Speakers with Ataxic Dysarthria: An Auditory Free- Classification Approach

Abstract

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 (Hartelius et al., 2000) as a possible explanation of this variability. 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 (Clopper, 2008) 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 (AMR) and connected speech (1-2 sentences). Listener ratings were then compared with a priori expert determinations of speakers who fit the instability subgroup profile and the inflexibility subgroup profile. Results of both the free classification and guided classification listening paradigms provided definitive evidence of subgroups, particularly for the AMR task, in the context of excellent interrater reliability. This study supports 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 subtype research.