Thesis (M.S.)--University of Florida, 2005. / Typescript. Title from title page of source document. Document formatted into pages; contains 66 pages. Includes Vita. Includes bibliographical references.

Background: Language impairment associated with Motor Neurone Disease (MND) has been documented since the late 19th century, yet little is understood about the pervasiveness or nature of these deficits. The common clinical view among healthcare professionals is that communication difficulties can be attributed solely to the motor speech disorder dysarthria. Recent literature raises the possibility of more central processing deficits. Impairments in naming ability and comprehension of complex grammatical constructs have been frequently reported in some patients with MND. However, there is now growing evidence of spelling impairment, which could suggest the contribution of a more phonologically based deficit. In addition, the close relationship between MND and frontotemporal dementia (FTD) raises questions about the connection between the language impairments seen in MND patients and those documented in patients with the primary progressive aphasia (PPA) syndromes associated with FTD. Aims: This thesis examines the nature of speech and language deficits in people with MND and the extent to which expressive communication impairment can occur above and beyond dysarthria. In particular, the study explores: i) to what extent these language impairments can be attributed to deficits in working memory, executive functioning and/or disease severity; ii) what spelling errors can reveal about the integrity of lexical, phonological and orthographic processing; iii) whether similar patterns of impairment can be seen in PPA syndromes; iv) the relationship between language impairment and bulbar onset; and v) the impact these findings have on clinical management of MND patients. Methods: MND patients from across Scotland with changes in speech and/or language were tested using a neuropsychological battery of experimental and standardised tests of naming, spelling, syntactic comprehension, prosody and phonological and orthographical awareness. Patients were also screened for levels of dysarthria, executive functioning and working memory deficits, and results compared to those of matched controls. Findings: As a group, MND participants performed significantly worse than matched controls on measures of naming, spelling, orthographical awareness, grammatical comprehension, affective prosody and verbal fluency, but not working memory. However, based on patterns of individual impairment, of which spelling impairment formed a distinctive marker, the patient group divided into dichotomous subgroups, with 44% of participants categorised as ‘linguistically impaired’, while the remainder displayed little to no impairment. Those participants identified as linguistically impaired did not differ significantly from other MND participants on measures of disease severity, disease duration or dysarthria severity, although significantly more bulbar onset than limb onset participants were linguistically impaired. Spelling error patterns were suggestive of deficits at both a lexical and sublexical level, and were comparable to those reported in PPA literature. These findings suggest that dysarthria may be masking linguistic deficits in almost half of dysarthric MND patients, and highlight the importance of multidimensional assessment of language for effective clinical management.

Auditory comprehension, the ability to understand spoken language, consists of a number of different auditory processing skills. In the five studies presented in this thesis I investigated both intact and impaired auditory comprehension at different levels: voice versus phoneme perception, as well as single word auditory comprehension in terms of phonemic and semantic content. In the first study, using sounds from different continua of ‘male’-/pæ/ to ‘female’-/tæ/ and ‘male’-/tæ/ to ‘female’-/pæ/, healthy participants (n=18) showed that phonemes are categorised faster than voice, in contradistinction with the common hypothesis that voice information is stripped away (or normalised) to access phonemic content. Furthermore, reverse correlation analysis suggests that gender and phoneme are processed on the basis of different perceptual representations. A follow-up study (same paradigm) in stroke patients (n=25, right or left hemispheric brain lesions, both with and without aphasia) showed that lesions of the right frontal cortex (likely ventral inferior frontal gyrus) leads to systematic voice perception deficits while left hemispheric lesions can elicit both voice and phoneme deficits. Together these results show that phoneme processing is lateralized while voice information processing requires both hemispheres. Furthermore, this suggests that commencing Speech and Language Therapy at a low level of acoustic processing/voice perception may be an appropriate method in the treatment of phoneme perception impairments. A longitudinal case study (CF) of crossed aphasia (rare acquired communication impairment secondary to lesion ipsilateral to the dominant hand) is then presented alongside a mini-review of the literature. Extensive clinical investigation showed that CF presented with word-finding difficulties related to impaired auditory phonological analysis, while functional Magnetic Resonance Imaging (fMRI) analyses showed right hemispheric lateralization of language functions (reading, repetition and verb generation). These results, together with the co-morbidity analysis from the mini-review, suggest that crossed aphasia can be explained by developmental disorders which cause partial right lateralization shift of language processes. Interestingly, in CF this process did not affect voice lateralization and information processing, suggesting partial segregation of voice and speech processing. In the last two studies, auditory comprehension was examined at the single word level using a word-picture matching task with congruent (correct target) and incongruent (semantic, phonological and unrelated foils) conditions. fMRI in healthy participants (n=16) revealed a key role of the pars triangularis (phonological processing), the left angular gyrus (semantic incongruency) and the left precuneus (semantic relatedness) in this task – regions typically associated via the arcuate fasciculus and often impaired in aphasia. Further investigation of stroke patients on the same task (n=15) suggested that the connections between the angular gyrus and the pars triangularis serve a fundamental role in semantic processing. The quality of a published word-picture matching task was also investigated, with results questioning the clinical relevance of this task as an assessment tool. Finally, a pilot study looking at the effect of a computer-assisted auditory comprehension therapy (React2©) in 6 stroke patients (vs. 6 healthy controls and 6 stroke patients without therapy) is presented. Results show that the more therapy patients carry out the more improvement is seen in the semantic processing of single nouns. However, these results need to be reproduced on a larger scale in order to generalise any outcomes. Overall, the findings from these studies present new insight into, as well as extending on, current cognitive and neuroanatomical models of voice perception, speech perception and single word auditory comprehension. A combinatorial approach to cognitive and neuroanatomical models is proposed in order to further research, and thus improve clinical care, into impaired auditory comprehension.

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Thesis (M.A.)--Ohio University, August, 2007. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph. D.)--Indiana University, 1984. / Vita. Includes bibliographical references (p. 82-85).

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Thesis (M.Ed.)--University of Hong Kong, 1982. / Also available in print.