The differential effects of dysarthria type on lexical segmentation

• Published in: The Journal of the Acoustical Society of America 2009-04, Vol.125 (4_Supplement), p.2531-2531
• Main Authors: Liss, Julie M., Spitzer, Stephanie M., Lansford, Kaitlin, Caviness, John N.
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4783551

Although intelligibility deficits are common across various forms of dysarthria, it was hypothesized that the causes of intelligibility reductions depend on the ways the degraded signal challenges listener cognitive-perceptual strategies. This hypothesis was confirmed by analyzing the lexical boundary errors (LBE) elicited by 44 speakers with one of four forms of dysarthria (ataxic, hypokinetic, hyperkinetic, mixed spastic-flaccid). Error patterns from 60 listener transcripts revealed reliance on metrical stress to segment the 80 six-syllable phrases. However, reductions and disturbances in the acoustic cues to syllabic stress associated with each form of dysarthria resulted in different LBE patterns. Explanations for these unique patterns are found, in part, in the metrical structures of the dysarthric speech. For example, the temporal relationships among stressed and unstressed syllables varied widely in hyperkinetic speech, which ostensibly prevented listeners from optimally exploiting metrical stress as a cue for segmentation. The equal-even temporal structure of the spastic-flaccid speech resulted in the highest proportion of boundary insertions. The presence of interword pauses facilitated the assignment of word onset to strong syllables. Results will be presented relative to models of lexical segmentation and clinical implications for targets of remediation in the dysarthrias. [Work supported from NIH-NIDCD 5R01 DC6859.]