Cognitive, social and emotional processes in unawareness of illness following stroke
Doctoral Thesis
2015
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University of Cape Town
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Disturbances in unawareness can offer an important avenue to investigate the neurocognitive processes involved in the construction of the bodily self. The general aim of the present thesis was to advance the current state of knowledge on a prototypical disorder of self-awareness, anosognosia for hemiplegia (AHP): unawareness of motor deficits contralateral to a brain lesion. Based on insights gained from both clinical and experimental research on anosognosia, it is argued that purely sensorimotor accounts do not explain several features of the syndrome, such as the delusional and emotional aspects. Therefore a revision of prevailing, modular theories of anosognosia is proposed that take into account the involvement of affective and so cial processes. Accordingly, the thesis aimed to: (1) investig ate the emotional and social factors that underlie motor unawareness; (2) identify the neurocognitive factors and neuroanatomical correlate that underlie such factors; and (3) develop potential, bedside rehabilitation interventions for AHP that are informed by the above investigations. These aims were achieved using an integrative methodological approach, which combined neuropsychological testing, psychophysiological experiments and neuroimaging methods. A series of experiment al group investigations and clinical case studies were conducted in 53 adult patients with right-hemisphere strokes. The main results of these studies showed that: (i) motor awareness is modulated by negative, but not positive emotion in a social context; (ii) anosognosia is associated with specific deficits in 3rd person perspective taking in visual-spatial and mentalising tasks; (iii) anosognosia is modulated by 'other' referent and 3rd person verbal and visual perspective taking. These experimental findings on the role of emotion and social processes in AHP were in turn used to develop a rehabilitation intervention applied in two case studies that showed promising results. Additionally, converging neuroimaging evidence provided support for the unique involvement of the inferior frontal gyrus, insula ribbon, supramarginal and superior temporal gyrus, and dorsal frontal white matter in anosognosia, which have well-established links to motor monitoring, subjecting feelings and self-awareness, and the proposed 'mentalising network'. These finding are in support of a proposed new account of AHP, which move s away from traditional modular theories of anosognosia, towards a dynamic model of the construction of the bodily self.
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Besharati, S. 2015. Cognitive, social and emotional processes in unawareness of illness following stroke. University of Cape Town.