Julie Liss - US grants

form /pattern perception; psychoacoustics; speech disorders; human subject;

DESCRIPTION (provided by applicant): There currently exists no functional model of speech perception in dysarthria that captures the critical interface between speech signal characteristics and the cognitive-perceptual processes brought to bear on that signal by the listener. Yet such a model is necessary, not only to explain intelligibility deficits, but also to guide and justify treatment decisions in clinical practice. Two series of experiments will be undertaken, which focus on the signal-listener interface for lexical segmentation, or the perceptual task of parsing the continuous acoustic stream into discrete words. The first set will focus on the nature of the intelligibility deficit by examining speech perception errors among different forms and severity levels of dysarthria. This will define and establish the relationships among segmental and suprasegmental deficit patterns, dysarthria severity levels, and the perceptual consequences of each. The second set of experiments will focus on the sources of intelligibility gains, by directly manipulating listener constraints in a training paradigm. In both series of experiments, predictions proposed by two accounts of lexical segmentation will be tested. These include the Metrical Segmentation Strategy Hypothesis (MSS; Cutler & Norris, 1988; Cutler & Butterfield, 1992), and the Hierarchical Model of Speech Segmentation (HMSS; Mattys, S.L. The hierarchical model of speech segmentation. BBSRC, 2003-2006). Lexical boundary error and segmental analyses will be conducted on listeners' transcription of phrases produced by speakers with different forms and severities of dysarthria. It is predicted that, for a given pattern of dysarthria (form), there will be evidence of differences in the effectiveness of listeners' cognitive-perceptual strategies, directly traceable to severity of speech deficit. For a given level of speech deficit severity, there will be evidence of differences in the effectiveness of listeners' cognitive-perceptual strategies, directly traceable to dysarthria form. By examining perceptual error patterns elicited in a training paradigm, it will be possible to identify which aspects of the acoustic signal are of perceptual salience in a default mode, and which features can be elevated in perceptual salience via training. Information learned about differences in the perceptual processing of different forms and severities of dysarthria will be used to develop a model of speech intelligibility deficits in dysarthria, and will have applicability to management programs in speech rehabilitation.

DESCRIPTION (provided by applicant): Reduced intelligibility is the at the heart of the communication disorder associated with the dysarthrias and other speech production deficits, causing functional and societal limitations and disabilities, and undermining quality of life. At present, the most common clinical approach to intelligibility assessment is subjective in nature. Subjective impressions, although expedient to collect, are by their very nature vulnerable to clinician bias. Safeguards to enhance reliability and validity of subjective impressions (e.g., naive listeners, listen panels, etc) are prohibitively high cost for typical clinical settings. Thee is an urgent need for the development of dependent measures sensitive enough to detect speech changes in early disease; document the efficacy of behavioral, surgical or pharmacological interventions; and track speech changes associated with disease progression. In this translational research, we propose to use the well-developed principles of intelligibility quantification that have been standardized in speech telecommunications and to develop and validate new measures of intelligibility in clinical populations. Specifically, we aim to develop a process by which the intelligibility of dysarthric speech can be validly and reliably quantified relative to a reference control sample; and to algorithmically isolate the source(s) of intelligibiity degradation along certain dimensions to augment clinical practice. In addition to integrating existing intelligibility metrics within our developed framework, we intend to instantiate new metrics, specifically optimized for dysarthric speech, based on insight and data gained during a previous NIH-funded grant. Preliminary results show promise that the proposed approach will yield a successful framework for quantifying intelligibility. These results indicate existing telecommunication-based intelligibility metrics accurately capture intelligibility degradation for noisy speech. Further, we show that the same metrics can accurately capture differences in intelligibility between three dysarthric speakers of differing intelligibility levels. Finally, we how that a subset of the envelope modulation spectra features, developed previously in our lab, are remarkably predictive of a speaker's intelligibility. The results of the proposed research will for the basis for a subsequent R01 proposal for the development of a fully functional clinical tool to objectively quantify and track speech intelligibility and its causal components. PUBLIC HEALTH RELEVANCE: There is an urgent need for the development of dependent measures sensitive enough to detect speech changes in early disease; document the efficacy of behavioral, surgical or pharmacological interventions; and track speech changes associated with disease progression. Reduced intelligibility is the at the heart of the communication disorder associated with the dysarthrias and other speech production deficits, causing functional and societal limitations and disabilities, and undermining quality of life. We aim to develop a process by which the intelligibility of dysarthric speech can be validly and reliably quantified relative to a reference control sample; and to algorithmically isolate the source(s) of intelligibiity degradation along certain dimensions to augment clinical practice.

DESCRIPTION (provided by applicant): By our estimation 93% of people with dysarthria worldwide, or 43 million people, either do not speak English or are bi- or multi-lingual. However, the consequences of dysarthria on communicative function in languages other than English are virtually unknown. This is because our mechanisms for describing and treating dysarthria are English-language centric-that is, based on the rhythm and phonology of the English language. However, the differing rhythm patterns and speech sounds of other languages make it patently clear that dysarthria in other languages (e.g., Spanish) will result in very different production consequences for people with dysarthria, and very different perceptual challenges for their communicative partners. While that is the case, there has been no systematic research on the consequences of motor speech disorders across languages and there is no mechanism to describe, or address, dysarthria in languages other than English. This presents a significant health-care issue here in the US, in which over 500,000 of the estimated three million people with dysarthria are either bilingual, or non-English speakers. We can address this issue. The overall goal of this proposal is to build, and make freely available, a cross-linguistic audio-visul database of dysarthric speech. The database will be comprised of speech samples from people with dysarthria who speak English and/or Spanish and all data will be tagged with biographical characteristics, time-aligned orthographic transcription, and quantified acoustic data related to patterns of speech degradation in rhythm patterns, articulatory integrity, and intelligibility acoustic metrics. This database will be easy to search, and data will be easy to export. Our international collaboration is uniquely placed to make this happen. We have existing infrastructure and resources that can be leveraged to build the database; we have developed a working model through which to explore cross-linguistic communication function in dysarthria; we have developed and tested battery of automated acoustic metrics that capture aspects of speech rhythm, articulatory integrity, and source and filter characteristics; and we will develop a universal speech stimuli template from which to study communication function cross-linguistically. This proposal brings these components together, and serves as the foundation for a subsequent R01 proposal aimed at hypothesis driven investigations of dysarthria, language, and communicative function in English and Spanish. The development of this research platform offers the opportunity for rapid advances in scientific knowledge, which can be directly translated to clinical practice.

The trained ear of the speech-language pathologist is the gold standard assessment tool for clinical practice in motor speech disorders. However, perceptual judgments are vulnerable to bias and their relationship with estimates of listener intelligibility ? the final arbiter of speech goodness ? is indeterminate. Interpretable, objective, and robust outcome measures that provide targets for treatment are urgently needed in order to provide more precise care and reliably monitor patient progress. Based on theoretical models of speech perception, in our previous grants we have developed a novel set of outcome measures that provide a multi- dimensional intelligibility profile (MIP) by using custom speech stimuli and a new coding strategy that allows us to capture the types of errors that listeners make when listening to dysarthric speech. This has led to a more complete intelligibility profile that codifies these errors at different levels of granularity, from global to discrete. Simultaneously, we have also developed a computational model for evaluation of dysarthric speech capable of reliably estimating a limited set of intelligibility measures directly from the speech acoustics. To date, both the outcome measures and the objective model have been evaluated on cross-sectional data only. In this renewal application, our principal goal is to evaluate specific hypotheses regarding expected changes in this multidimensional intelligibility profile as a result of different intervention instruction conditions (loud, clear, slow). A secondary goal of the proposal is to further refine our objective model to predict the complete intelligibility profile and to evaluate its ability to detect intelligibility changes within individual speakers. This is critical for clinicians who currently have no objective ways to assess the value of their interventions. With the aim of improving the standard of care through technology, the long-term goal of this proposal is to develop stand-alone objective outcome measures for dysarthria that can provide clinicians with reliable treatment targets. Such applications have the potential to dramatically alter the current standard of care in speech pathology for patients with neurological disease or injury. Furthermore, these applications also have the potential to reduce health disparities by partially automating clinical intervention and providing easier access to these services to those in remote areas or in underdeveloped countries.  

Project Summary/Abstract With telepractice becoming an increasingly popular, indeed necessary, alternative to clinic visits, speech- language pathologists (SLPs) evaluate speech that is audio captured and transmitted remotely via a teleconferencing solutions (e.g. Zoom). All popular teleconferencing applications use speech compression algorithms based on linear predictive coding (LPC) to reduce bandwidth required for speech transmission. LPC compression algorithms decompose speech into phonatory source and articulatory filter parameters, which are then independently vector quantized and temporally smoothed based on schemes that have been developed and optimized for compressing speech sampled from the general population. In this way, speech is transmitted with the least number of audible artifacts and the highest level of intelligibility for the given internet connection constraints. Because LPC algorithms are optimized using large corpora of typical speech, they are fundamentally not well-suited for faithfully transmitting the amount of distortion or noise commonly present in the dysarthric speech signal, and articulation and voice features are particularly vulnerable to corruption. In this proposal the aim is to systematically characterize the impact of speech compression algorithms commonly used in telepractice platforms on speech intelligibility, perceptual evaluation, and acoustic measurement. This is done via two aims: SA1: Evaluate the effects of teleconferencing speech compression algorithms at three internet bandwidth levels on the perceptual and acoustic assessment of dysarthric speech Existing high-fidelity audio recordings of words and sentences and sustained phonations from 20 speakers with various dysarthrias will be encoded at three compression rates to simulate low-, moderate-, and high- bandwidth internet connectivity. Twenty SLPs will transcribe the samples to attain intelligibility measures for the original and encoded words and sentences; and perceptually rate vocal quality on sustained phonations. Acoustic measures of articulation and voice will be extracted. Within-subject statistical models will evaluate impact of bandwidth condition on perceptual and acoustic outcomes within speech tasks. SA2: Compare outcomes for dysarthric speech recorded in a telepractice session (compressed) versus that recorded simultaneously in-person via smartphone application (uncompressed). Fifteen speakers with dysarthria will participate in simulated telepractice speech assessments administered by SLPs. Subsequently, recordings from session (compressed) and simultaneously recorded in-person samples (uncompressed) will be scored by SLPs. In-person recordings will also be compressed as in SA1 conditions. Acoustic metrics will be extracted from all samples. Within-subject statistical models will evaluate sample differences across conditions (uncompressed, compressed during telepractice, and low- moderate- and high- bandwidth compression levels). Results will inform the limits of telepractice for dysarthria evaluation.