Effects of Speaking Rate on Variability of Second Formant Frequency Transitions in Dysarthria.
Frits van Brenk, Anja Lowit, Kris Tjaden
PMID 37769645WHAT IT FOUND
Measuring how much second formant slopes vary from repetition to repetition, rather than just averaging them, better identified ataxic dysarthria and correlated with intelligibility.
Averaged slopes were better at identifying hypokinetic dysarthria. Speaking rate changes revealed these differences.
Key findings
01Variability measures of second formant slopes were significantly higher in speakers with ataxic or ataxic-spastic dysarthria compared to those with hypokinetic dysarthria and controls.
02Averaged global and maximum instantaneous slope measures were lower in speakers with hypokinetic dysarthria compared to controls, but did not distinguish ataxic dysarthria from controls.
03Variability measures, but not averaged measures, of second formant slopes correlated negatively with intelligibility scores.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The group with ataxic dysarthria was small (n=9) and varied in underlying etiology. Severity was not matched between groups; the ataxic group had more severe dysarthria than the hypokinetic group, which may confound the finding that variability measures were more sensitive to the ataxic group. The task involved repeating a single memorized sentence, which may not reflect natural speech demands. Self-pacing during rate changes introduced variability in how participants implemented the instructions.
Declared interests
The authors have no conflicts of interest to declare. The study was supported by NIH (Extramural) and non-U.S. government research support.
The easy way to misread this
Do not assume that variability measures are universally superior to averaged measures for all dysarthria types. Averaged slopes were more effective at distinguishing hypokinetic dysarthria from controls, while variability was key for ataxic dysarthria. The choice of metric should depend on the suspected subtype.