More than words: Recognizing speech of people with Parkinson's disease

Parkinson’s disease (PD) is the fastest-growing neurological disorder in the world, with approximately 10 million people currently living with the diagnosis. Hypokinetic dysarthria (HD) is one of the symptoms that appear in early stages of the disease progression. The main aim of this dissertation is to gain insights into listeners’ impressions of dysarthric speech and to uncover acoustic correlates of those impressions. We do this by exploring two sides of communication: speech production of people with PD, and listeners’ recognition of speech of people with PD. Therefore, the studies in this dissertation approach the topic of speech changes in PD from both the speakers' side - via acoustic analysis of speech, and the listeners' side - via experiments exploring the influence of expertise and language background on recognition of speech of people with PD. Moreover, to obtain a more comprehensive picture of these perspectives, the studies of this dissertation are multifaceted, explore cross-linguistic aspects of dysarthric speech recognition and include both cross-sectional and longitudinal designs. The results demonstrate that listeners' ability to recognize speech of people with PD as unhealthy is rooted in the acoustic changes in speech, not in its content. Listeners’ experience in the fields of speech and language therapy or speech sciences affect dysarthric speech recognition. The results also suggest that tracking speech parameters is a useful tool for monitoring the progression and/or development of dysarthria and objectively evaluating long-term effects of speech therapy

Prosodic and Segmental Correlates of Spontaneous Dutch Speech in Patients with Parkinson’s Disease:A Pilot Study

This study investigates the acoustic correlates of prosody and vowel articulation in Dutch individuals with Parkinson’s Disease (PD). We compared prosodic and segmental acoustic measures in spontaneous monologues in PD patients to those in elderly healthy controls matched for age and gender. For the prosodic measurements of pitch variability, span and speech rate, we analysed fundamental frequency and intensity. For articulation measurements, the first two formants were calculated from Dutch corner vowels extracted from the speech signal. Results show a monopitch trend, reduced speech rate, centralization of the formant frequencies and reduced first formant variability in individuals with PD compared to control group

Phonetic Realisation and Phonemic Categorisation of the Final Reduced Corner Vowels in the Finnic Languages of Ingria

Individual variability in sound change was explored at three stages of final vowel reduction and loss in the endangered Finnic varieties of Ingria (subdialects of Ingrian, Votic and Ingrian Finnish). The correlation between the realisation of reduced vowels and their phonemic categorisation by speakers was studied. The correlated results showed that if V was pronounced > 70%, its starting loss was not yet perceived, apart from certain frequent elements, but after > 70% loss, V was not perceived any more. A split of 50/50 between V and loss in production correlated with the same split in categorisation. At the beginning of a sound change, production is, therefore, more innovative, but after reanalysis, categorisation becomes more innovative and leads the change. The vowel a was the most innovative in terms of loss, u/o were the most conservative, and i was in the middle, while consonantal palatalisation was more salient than labialisation. These differences are based on acoustics, articulation and perception

How expertise and language familiarity influence perception of speech of people with Parkinson’s disease

Parkinson’s disease (PD) is a progressive neurological disorder characterized by several motor and non-motor manifestations. PD frequently leads to hypokinetic dysarthria, which affects speech production and often has a detrimental impact on everyday communication. Among the typical manifestations of hypokinetic dysarthria, speech and language therapists (SLTs) identify prosody as the most affected cluster of speech characteristics. However, less is known about how untrained listeners perceive PD speech and how affected prosody influences their assessments of speech. This study explores the perception of sentence type intonation and healthiness of PD speech by listeners with different levels of familiarity with speech disorders in Dutch. We investigated assessments and classification accuracy differences between Dutch-speaking SLTs (n = 18) and Dutch/non-Dutch speaking untrained listeners (n = 27 and n = 124, respectively). We collected speech data from 30 Dutch speakers diagnosed with PD and 30 Dutch healthy controls. The stimuli set consisted of short phrases from spontaneous and read speech and of phrases produced with different sentence type intonation. Listeners participated in an online experiment targeting classification of sentence type intonation and perceived healthiness of speech. Results indicate that both familiarity with speech disorders and with speakers’ language are significant and have different effects depending on the task type, as different listener groups demonstrate different classification accuracy. There is evidence that untrained Dutch listeners classify PD speech as unhealthy more accurately than both trained Dutch and untrained non-Dutch listeners, while trained Dutch listeners outperform the other two groups in sentence type classification