Automating Intended Target Identification for Paraphasias in Discourse using a large language model

Purpose: To date, there are no automated tools for the identification and fine-grained classification of paraphasias within discourse, the production of which is the hallmark characteristic of most people with aphasia (PWA). In this work, we fine-tune a large language model (LLM) to automatically predict paraphasia targets in Cinderella story retellings. Method: Data consisted of 332 Cinderella story retellings containing 2,489 paraphasias from PWA, for which research assistants identified their intended targets. We supplemented these training data with 256 sessions from control participants, to which we added 2,415 synthetic paraphasias. We conducted four experiments using different training data configurations to fine-tune the LLM to automatically “fill in the blank” of the paraphasia with a predicted target, given the context of the rest of the story retelling. We tested the experiments\u27 predictions against our human-identified targets and stratified our results by ambiguity of the targets and clinical factors. Results: The model trained on controls and PWA achieved 50.7% accuracy at exactly matching the human-identified target. Fine-tuning on PWA data, with or without controls, led to comparable performance. The model performed better on targets with less human ambiguity and on paraphasias from participants with fluent or less severe aphasia. Conclusions: We were able to automatically identify the intended target of paraphasias in discourse using just the surrounding language about half of the time. These findings take us a step closer to automatic aphasic discourse analysis. In future work, we will incorporate phonological information from the paraphasia to further improve predictive utility

Towards Automatic Speech-Language Assessment for Aphasia Rehabilitation

Speech-based technology has the potential to reinforce traditional aphasia therapy through the development of automatic speech-language assessment systems. Such systems can provide clinicians with supplementary information to assist with progress monitoring and treatment planning, and can provide support for on-demand auxiliary treatment. However, current technology cannot support this type of application due to the difficulties associated with aphasic speech processing. The focus of this dissertation is on the development of computational methods that can accurately assess aphasic speech across a range of clinically-relevant dimensions. The first part of the dissertation focuses on novel techniques for assessing aphasic speech intelligibility in constrained contexts. The second part investigates acoustic modeling methods that lead to significant improvement in aphasic speech recognition and allow the system to work with unconstrained speech samples. The final part demonstrates the efficacy of speech recognition-based analysis in automatic paraphasia detection, extraction of clinically-motivated quantitative measures, and estimation of aphasia severity. The methods and results presented in this work will enable robust technologies for accurately recognizing and assessing aphasic speech, and will provide insights into the link between computational methods and clinical understanding of aphasia.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/140840/1/ducle_1.pd

Cognitive control and language network connectivity associated with language production in aphasia

Aphasia is the breakdown of language comprehension and production due to an acquired brain injury of the left hemisphere. Investigation of the neurological underpinnings of aphasia have advanced from post-mortem investigation of specific regions in the 1800s to the utilization of brain imaging technology to understand brain networks. These approaches have helped us to appreciate the reorganization of the brain and its networks post stroke, particularly as it relates or is modified for adequate versus impaired performance. Research into neuroplastic changes can elucidate differences between healthy and lesioned brains. Furthermore, identification of adaptive (or maladaptive) neuroplastic changes can also inform diagnostics or aid in monitoring the neuroplastic effects of evidence-based treatment. This study utilized resting state functional MRI to characterize graph theory metrics of language (LN) and cognitive control networks (frontoparietal, FPN) in 21 persons with aphasia (PWA) and 18 healthy controls (HC). This study further investigated the relationship between strength of connectivity and semantic access and errors in PWA during a picture description task. When comparing resting state network connectivity of the LN in PWA vs. HC, many edges (10/14) and node degree hubs (3/3) were common to both groups for the LN, suggesting that an inherent network that remains relatively intact even post-stroke. Analyses yielded similar results for resting state FPN network connectivity with common edges and node degree hubs. When investigating correlations between network edges and language measures, correlations between FPN edges and CIU’s and retracing suggested the importance of right hemisphere and ‘healthy’ edge integrity

A longitudinal study of narrative discourse in post-stroke aphasia

Background: Previous findings have demonstrated the importance of discourse analysis in post-stroke aphasia, as it allows for in-depth examination of language impairment and represents key components of functional communication. However, little is known about the recovery of discourse over time. Aims: The main aim of this study is to measure the longitudinal changes in descriptive discourse production from the acute to chronic stages of post-stroke aphasia recovery. The secondary aim is to explore the association between discourse measures and overall language impairment severity measures at different testing points. Methods & Procedure: Seventeen French Canadian speakers with various types and severities of aphasia following a first left middle cerebral artery stroke participated in this study. They underwent three language assessments (acute: 0 to 72 hours; subacute: 7 to 14 days; chronic: 6 to 12 months post-onset). The picture description from the Western Aphasia Battery was analyzed at three time points. Changes in terms of thematic informativeness and microstructural variables were analyzed. Outcomes & Results: Regarding the micro-structural variables, the mean length of utterances (MLU) and the number of words per minute showed significant positive changes between the acute and chronic phases. For the thematic informativeness measures, the number of thematic units (TUs), the number of thematic units per minute (TUs/min) and the number of thematic units per utterance (TUs/utt) 4 increased significantly between the acute and chronic phases. Positive correlations between TUs and MLU in the acute phase and a general language impairment severity measure in the acute and chronic phases suggest a relationship between these measures and global language performance suggesting the potential predictive value of these variables in the acute phase. Conclusions & Implications: These findings support the use of thematic units in descriptive discourse analysis during an acute clinical examination of language as they require minimal additional time to score and track changes in post-stroke aphasia recovery. They capture long-term changes in discourse abilities and appear related to overall language measures in both the acute and chronic stages of recovery. The interpretation of the changes in MLU and the number of words per minute is less straightforward, as improvements in these measures carry different interpretations depending on the type of aphasia. Nonetheless, further studies are required to investigate test-retest reliability and the effect of therapy on the changes observed over time when using thematic units to document change in discourse

Cross-Generic Dimension Of The Production Of Phonological Paraphasias And Neologisms By People With Aphasia

Taking into account the still pending problem of uniformity versus heterogeneity with which the phonological deficit manifests itself across various aphasia syndromes as well as the virtual absence of any cross-generic explorations of the quantitative and qualitative production patterns of phonological and neologistic paraphasias, we have set the goal of enriching the present-day body of aphasiologic and neurolinguistic knowledge with novel theoretical and practical insights by getting a number of relevant questions answered. These include the ones about the syndrome-universality versus specificity of phonological errors, the effect of discourse elicitation genre on the number of erroneous productions and the diversity of their categories alongside the effect of within-genre task complexity on the phonological output of Russian-speaking individuals diagnosed with five different types of aphasia. To accomplish our goal, we have conducted a rigorous quantitative and qualitative hierarchical cluster analysis of the phonological errors detected in the interview samples of 18 participants whose oral productive performance on the tasks belonging to four distinct discourse genres was recorded on a high-quality sound-recording device and transcribed using the combination of the Jefferson Transcription System and the International Phonetic Alphabet one. The results obtained demonstrate that the phonological error production patterns cannot be relied on in distinguishing various aphasia types. They also show that each discourse genre is marked by its own degree of mental processing complexity and is, thus, associated with a numerically distinct picture of errors. Moreover, the degree of task complexity has been found to be a matter of individual perception. Last but not least, the previous researchers’ findings pertaining to paraphasias have been compared to our data, and some of the earlier structural hypotheses have been unsupported. Our study is expected to be of great value and utility from the viewpoint of furthering the development of theoretical knowledge about the phonological breakdown in the language disorder under scrutiny specifically from the perspective of aphasics’ engagement in everyday discourse situations, refining the existing speech production models or developing new more realistic and viable ones, and generating ideas for practical solutions in speech-language pathology

Doctor of Philosophy

dissertationThe verb plays a critical role in sentence production, but verb production is commonly impaired in aphasia. The verb is therefore an important treatment target for aphasia treatments. The verb appears to have a network structure of meaning within the mental lexicon, and existing treatments, such as Verb Network Strengthening Treatment (VNeST) and “verb is core” treatment approach naming rehabilitation theoretically by expanding this network structure. However, these and other verb naming treatments have focused nearly exclusively on verbs with high concreteness ratings. While high concreteness verbs are useful and common, recent evidence highlights the utility and frequency of low concreteness verbs in spoken language also. Thus the focus of current verb treatments on verbs with high concreteness omits a set of verbs that are potentially useful for persons with aphasia. Therefore, a treatment was designed to improve the accuracy of low concreteness verb naming in persons with aphasia. The novel treatment was largely based on VNeST and emphasized the network structure of the mental representation of target verbs by pairing them with common subjects and objects. Three adult persons with nonfluent aphasia participated in a single-subject research design study examining the feasibility of the treatment for improving verbal naming of low concreteness verbs. Results from the study indicated possible changes associated with the treatment for two of the three participants, though these changes were limited in magnitude. Treatment performance data suggested possible improvements in verb processing that were not reflected in the primary outcome measure. Thus, future research is warranted and should focus on further enriching the mental verb network representations of target verbs with low concreteness and on refining relevant outcome measures

Lesions, lemmas and lehapu : anomia in two Sesotho-English bilingual speakers.

Rationale: Aphasia and anomia affect the communication abilities of thousands of South African stroke survivors. Therapy provision in South Africa is a challenging endeavour. Clinicians must provide therapy to clients who speak languages which have rarely, if ever, been the focus of clinical study. Models developed for use with clients who speak English or related languages may not be suitable for speakers of other, parametricallydiverse languages. Bilingualism is widespread in South Africa, yet therapeutic insights on how best to treat bilingual speakers are only beginning to inform clinical research and practice. Time and financial support are also lacking in many clinical settings. Aim: This study represents an attempt to establish which of four treatment conditions (initial phoneme cueing, codeswitch1 cueing, true phonemic cueing and prosodic cueing) is most effective at facilitating improved naming performance in two Sesotho-English bilingual speakers with post-stroke anomia. Methodology: Commercially-available tests of naming ability were found to be statistically invalid since they seemed to assess familiarity with Western culture and artifacts rather than naming ability. Working in conjunction with ten neurologically unimpaired Sesotho speakers living in the Northern Free State, community-referenced words lists were developed for use in this study. Two bilingual Sesotho-English speakers with post-stroke anomia participated in this study. T. was assessed and found to present with classical anomia, while S. presented with output anomia. T.’s word finding difficulties are characterized by pauses, use of vocalizers and part-whole productions, while S. tends to produce semantic paraphasias during anomic moments. 1 In keeping with trends present in research literature (e.g. Auer, 1999), codeswitching will be designated by a single, unhyphenated word. xi Each treatment condition (initial phoneme cueing, codeswitch cueing, true phonemic cueing and prosodic cueing) were allocated a word list. Pre-- and post-intervention scores of naming ability on these treatment lists and four lists of semantically related words were compared. The treatment conditions were evaluated in terms of three constructs commonly employed in anomia literature: potency (the degree to which a technique helps a speaker relearn words directly targeted in therapy), semantic generalizability (the degree to which a technique helps a speaker relearn words semantically related to those directly targeted in therapy) and persistence (the degree to which therapy effects are longlived.). The sign-test was used to determine statistical significance or otherwise. Results and discussion: Neither initial phoneme cueing nor codeswitch cueing were associated with statistically significant potency in either participant. Both true phonemic cueing and prosodic cueing were associated with statistically significant levels of potency in both participants. None of the treatment conditions were associated with statistically significant semantic generalizability in either participant. In the case of S., codeswitch cues appeared lead to an increase in the number and complexity of semantic paraphasias. No significant decrease in any of the gains made during the intervention portion of the study were noted one month after the conclusion of the study. Explanations for these results, informed by cognitive neuropsychology, are provided. Possible refinements to models of lexical retrieval in monolingual and bilingual speakers are postulated. Conclusion: The results of this study suggest that speech-language pathologists in South Africa should not rely solely on therapy approaches developed for use with Englishspeakers. Instead, a parametrically informed approach, which draws heavily on cognitive neuropsychological understandings of bilingual functioning, may be helpful in furnishing speech-language pathologists in South Africa with the tools they need to provide services. The local community needs to play a role in developing materials for use in therapy and assessment in challenging environments. New therapy techniques should be weighed against commonly used measures of therapy efficacy to determine the best course of treatment