Omar, R; (2012) Nonverbal processing in frontotemporal lobar degeneration. Doctoral thesis (PhD), UCL (University College London).

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Abstract

Frontotemporal lobar degeneration (FTLD) refers to a group of diseases characterised by focal frontal and temporal lobe atrophy that collectively constitute a substantial source of clinical and social disability. Patients exhibit clinical syndromes that are dominated by a variety of nonverbal cognitive and behavioural features such as agnosias, altered emotional and social responses, impaired regulation of physiological drives, altered chemical sense, somatosensory and interoceptive processing. Brain mechanisms for processing nonverbal information are currently attracting much interest in the basic neurosciences and deficits of nonverbal processing are a major cause of clinical symptoms and disability in FTLD, yet these clinical deficits remain poorly understood and accurate diagnosis is often difficult to achieve. Moreover, the cognitive and neuroanatomical correlates of behavioural and nonverbal cognitive syndromes in FTLD remain largely undefined. The experiments described in this thesis aim to address the issues of improving our understanding of the social and behavioural symptoms in FTLD through the integration of detailed neuro-behavioural, neuropsychological and neuroanatomical analyses of a range of nonverbal functions (including emotions, sounds, odours and flavours) with high-resolution structural magnetic resonance imaging (MRI). A prospective study of emotion recognition in various domains including music, faces and voices shows that music is especially vulnerable to the effects of damage in FTLD. A profile of brain atrophy associated with impaired emotion recognition in music is identified, comprising a distributed bilateral cerebral network involving areas previously implicated in representing and evaluating the emotional content of stimuli including mesial temporal structures, insula and their connections in the mesolimbic system. Prospective studies of face and chemosensory processing provide further insights into the neuroanatomical framework and structural neuroanatomy for face, odour and flavour processing deficits in FTLD. A profile of cognitive deficits in different components of face processing is shown which correlate with distinct but partly overlapping brain networks. Deficits in flavor and odour identification are shown in FTLD with neuroanatomical correlates involving temporal and limbic areas which include entorhinal cortex, hippocampus and parahipocampal gyrus. A detailed systematic study of music knowledge in two expert musicians with different dementia diseases, sematic dementia (SemD) and dementia with Lewy bodies (DLB), involving a series of novel neuropsychological experiments probing various dimensions of music knowledge, yields new insights into the cognitive architecture of music knowledge and the brain organization of nonverbal knowledge systems. This thesis therefore provides neuropsychological and imaging data in relation to various nonverbal cognitive processes in FTLD that can offer greater insights into our understanding of behavioural symptoms in this group of diseases as well as the cognitive architecture of hitherto relatively poorly understood nonverbal cognitive modalities such as music knowledge, emotion and chemosensory processing.

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