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[The effect of time-compressed speech on the perception of ataxic dysarthria: a report of two cases]
Virginie Woisard-Bassols1, Robert Espesser, Alain Ghio
1Laboratoire parole et langage, UMR6057 CNRS, Université de Provence, Aix-en-Provence, France. woisard.v@chu-toulouse.fr
Aim:
In cerebellar dysarthria, the lack of precision in the articulatory motions leads to a temporal dysregulation with a decreased rate of speech. That is, our hypothesis is that the signal distortions are linked to the slowness of speech and that the acceleration of the rate improves the intelligibility of speech.
Patients And Method:
Two patients with a cerebellar pathology and an ataxic dysarthria participated in the present study. Speech intelligibility was assessed subjectively by a visual analog scale, and objectively by the constant-stimulus method associated with an identification task of a target phoneme in real time. The SOLA algorithm was used to accelerate the speech stimuli. 144 test sentences were created at 3 speed rates: 48 sentences at 'natural speed' (without compression, VN), 48 sentences at 'intermediate speed' (50% of the maximum rate, VI) and 48 sentences at 'maximum speed' (mean rate of a control group of speakers, VM). The 144 test sentences, in 3 experimental conditions, were distributed over 3 lists, each listener hearing each sentence only once; 8 subjects were assigned to each list. The sentences were presented in random order. A subjective assessment was performed for the whole corpus. The statistical analysis was performed with a mixed logit model for the subjective scores and the reaction time and with a chi2 test for the errors.
Results:
For each patient, the odds of an improved intelligibility were significantly greater for the VI or VM condition than for the VN condition. The effect tended to be stronger for patient Z. From the VN to the VI condition, the satisfaction rate regarding the intelligibility increased from 78 to 87% for patient B and from 46 to 63% for patient Z (p = 0.03). There were fewer errors for the accelerated speech for patient Z. The acceleration had no effect on the reaction times in the phoneme identification task (F 2,(1,024) = 2.14, p = 0.12).
Conclusions:
In 2 cases of ataxic dysarthria, the perceived intelligibility was improved by a temporal acceleration of the speech disorders.
