Identifying Communicative Signals in Dysarthric Speech

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DESCRIPTION (provided by applicant): Dysarthria, a speech disorder resulting from damage to the brain or peripheral nerves leads to slow, imprecise, and poorly coordinated speech movements. For many individuals, speech is not a viable communication option. This has devastating consequences on quality of life. Despite severe dysarthria, many individuals continue to use vocalizations when interacting with familiar communication partners suggesting that reliable information is embedded in the dysarthric speech signal. Identifying these consistent vocal signals has the potential to afford many individuals with an alternative channel of communication. Previous work has assumed that salient information is primarily encoded in speech sound segments. Our recent investigations have shown that prosodic features such as fundamental frequency (perceived as pitch), intensity (perceived as loudness), and syllable duration also carry significant communicative information. We hypothesize that speakers with severe dysarthria have sufficient control of prosody, given that these features vary over slower time scales than segmental units such as phonemes and thus may be easier to produce. We have demonstrated control of prosody in isolated vowels and in phrases to mark question-statement contrasts. To extend beyond previous work we will study a more complex task of local syllable-level control of prosody that better approximates natural speech. Fifteen speakers with severe dysarthria and fifteen non-impaired controls will produce four-syllable phrases with stress placed on specified syllables to modulate the meaning of the phrase. To determine whether speakers with severe dysarthria can accurately signal stress, a group of 60 listeners will judge which syllable was stressed in each recording (Specific Aim 1). Statistical analyses will be performed to examine listener accuracy for each speaker and to compare results across speaker groups. To understand how speakers with dysarthria mark contrastive stress, we will extract and analyze several acoustic features including fundamental frequency, intensity, duration, pause and spectral tilt (Specific Aim 2). Separate analyses of variance will performed on each feature to quantify its importance in signaling stress and to determine feature-wise differences between speakers. Last, we will compare stress patterning in speakers with severe dysarthria and non-impaired speakers to gain a better understanding of acoustic correlates and compensatory mechanisms associated with signaling stress in dysarthria (Specific Aim 3). If speakers with dysarthria can reliably exploit prosodic cues, our findings will guide the development of intervention strategies that focus on the role of prosody for improving the effectiveness of natural communication, and the design of novel communication devices that leverage prosody as a communicative signal. Our ultimate goal is to understand the factors that lead to improved speaker expressiveness, and to leverage this knowledge to help individuals communicate more naturally and effectively, enabling them to engage more fully in educational, vocational, and social activities.