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Processing of nonverbal vocalisations in dementia

Sivasathiaseelan, Harri; (2021) Processing of nonverbal vocalisations in dementia. Doctoral thesis (Ph.D), UCL (University College London. Green open access

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Nonverbal emotional vocalisations are fundamental communicative signals used to convey a diverse repertoire of social and emotional information. They transcend the boundaries of language and cultural specificity that hamper many neuropsychological tests, making them ideal candidates for understanding impaired socio-emotional signal processing in dementia. Symptoms related to changes in social behaviour and emotional responsiveness are poorly understood yet have significant impact on patients with dementia and those who care for them. In this thesis, I investigated processing of nonverbal emotional vocalisations in patients with Alzheimer’s disease and frontotemporal dementia (FTD), a disease spectrum encompassing three canonical syndromes characterised by marked socio-emotional and communication difficulties - behavioural variant FTD (bvFTD), semantic variant primary progressive aphasia (svPPA) and nonfluent/agrammatic variant primary progressive aphasia (nfvPPA). I demonstrated distinct profiles of impairment in identifying three salient vocalisations (laughter, crying and screaming) and the emotions they convey. All three FTD syndromes showed impairments, with the most marked deficits of emotion categorisation seen in the bvFTD group. Voxel-based morphometry was used to define critical brain substrates for processing vocalisations, identifying correlates of vocal sound processing with auditory perceptual regions (superior temporal sulcus and posterior insula) and emotion identification with limbic and medial frontal regions. The second half of this thesis focused on the more fine-grained distinction of laughter subtypes. I studied cognitive (labelling), affective (valence) and autonomic (pupillometric) processing of laughter subtypes representing dimensions of valence (mirthful versus hostile) and arousal (spontaneous versus posed). Again, FTD groups showed greatest impairment with profiles suggestive of primary perceptual deficits in nfvPPA, cognitive overgeneralisation in svPPA and disordered reward and hedonic valuation in bvFTD. Neuroanatomical correlates of explicit laughter identification included inferior frontal and cingulo-insular cortices whilst implicit processing (indexed as autonomic arousal) was particularly impaired in those conditions associated with insular compromise (nfvPPA and bvFTD). These findings demonstrate the potential of nonverbal emotional vocalisations as a probe of neural mechanisms underpinning socio-emotional dysfunction in neurodegenerative diseases.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Processing of nonverbal vocalisations in dementia
Event: UCL (University College London
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
URI: https://discovery.ucl.ac.uk/id/eprint/10121453
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