The phenomenon whereby people suffering from an illness or disability seem to be unaware of their symptoms was termed anosognosia, by Joseph Babinksi in 1914 (Langer & Levine, 2014). Originally described as a specific inability to recognise or acknowledge left-sided hemiplegia after lesions to the right hemisphere of the brain, the term now incorporates unawareness of a range of post-stroke impairments, such as hemianopia (Bisiach, Vallar, Perani, Papagno & Berti, 1986), hemianaesthesia (Pia et al., 2014), aphasia (Cocchini, Gregg, Beschin, Dean & Della Sala, 2010) and unilateral neglect (Jehkonen, Ahonen, Dastidar, Laippala & Vilkki, 2000). Anosognosia has also been observed in association with several other disorders, including Alzheimer’s disease (Agnew & Morris, 1998) and traumatic brain injury (Prigatano, 2010a). While advances have been made in understanding anosognosia, there are still many contradictory findings in relation to the nature and expression of impaired self-awareness (Prigatano, 2010a), which are partly attributable to diverse methodological approaches. Furthermore, research into anosognosia frequently rests on the assumption that neurologically intact individuals have accurate insight into their own abilities, particularly in regard to motor skill. The experiments reported in this thesis highlight that this may be a false assumption. Through a series of interrelated studies, I demonstrate that the type of questions typically asked of anosognosic patients may be inappropriate to elicit the manifestations of chronic stage unawareness after a stroke, that underestimation may be just as prevalent as overestimation, and that healthy individuals are not always able to monitor whether their executed movements match their intended movements. Moreover, those with poorer motor skills are less able to judge movement successes and failures than their more skilled counterparts, suggesting a mechanism analogous to the anosognosia observed in clinical populations. Chapter 1 provides an overview of the main neuropsychological models that have been proposed to account for anosognosia for hemiplegia (AHP); unawareness in the context of other impairments is discussed in the introductions to individual chapters. Chapter 2 presents some background research investigating stroke clinicians’ knowledge of the lateralization of right hemisphere cognitive symptoms, and their judgements of the impact of selected symptoms on the lives of patients and caregivers. While the clinicians were equally able to identify cognitive symptoms associated with left or right brain damage, they were far more likely to misattribute symptoms to right brain damage, suggesting a lack of confidence in their knowledge of the cognitive functions of the right hemisphere. They also regarded anosognosia as having relatively low impact on the lives of patients and caregivers, in stark contrast with the highly negative impact reported in the literature (Jehkonen, Laihosalo & Kettunen, 2006a). Chapters 3 and 4 present two experimental studies investigating different facets of awareness in two groups of stroke patients. Chapter 3 reports the development and testing of a tool designed to measure chronic unawareness of functional difficulties, the Visual Analogue Test of Anosognosia for impairments in Activities of Daily Living (VATA-ADL), with preliminary data from a group of chronic stroke patients. Approximately one third of the patients exhibited mild or moderate levels of overestimation of their ability to carry out day-to-day activities. This contrasts with previous reports that anosognosia is rare in the chronic stages, a discrepancy that may be explained in part by the inappropriateness of the measures typically used to measure it. Overestimation was observed in both right-brain-damaged and left-brain-damaged patients, and was not associated with higher levels of cognitive impairment. The study reported in Chapter 4 examined whether acute stage stroke patients who under- or overestimated their motor skills, similarly under- or overestimated performance on cognitive tasks in the domains of language, memory and attention and executive function. Contrary to the many dissociations between unawareness of different impairment reported in the neuropsychological literature, this study found that patients classed as overestimators of motor ability were also overly optimistic about their cognitive abilities. Overestimators were more likely to have right hemisphere lesions, higher levels of general cognitive impairments, and specific deficits in attention and executive function. Furthermore, by including patients with a range of functional ability, this study revealed that participants were just as likely to underestimate as overestimate their abilities. This unique finding presents a challenge to anosognosia research, suggesting that there may be factors other than neurological damage that predispose stroke patients to over- or under-estimate their abilities and that a baseline of accurate self-insight among control populations cannot be assumed. Chapter 5 reports three different experiments conducted with younger and older, neurologically healthy adults. Using a target-directed reaching task, these experiments investigated whether the participants’ ability to monitor the success of their movements, on a trial by trial basis, depended upon their motor skill level, and whether participants with lower skill were inclined to overestimate their ability, in line with a famous observation from cognitive psychology that people who perform worst in a given task tend to be unaware of how poorly they are performing (Kruger and Dunning, 1999). Overall, the results demonstrated an association between higher accuracy levels and faster movement times, and better ability to monitor success and failure. To my knowledge, this represents that first evidence of a relationship between motor performance ability and self-monitoring ability in healthy individuals, highlighting that some of the mechanisms underpinning anosognosia may also be evident in neurologically intact populations. However, contrary to the findings from cognitive psychology, poor performance was not associated with a specific bias toward overestimation. A similar relationship between task performance and self-monitoring ability was also observed for a visual memory task. Chapter 6 discusses the implications of the results of the clinical and self-monitoring studies for neuropsychological models of anosognosia, particularly those based on motor planning and control, and considers potential ways forward for research in this field.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:735792 |
| Date | January 2017 |
| Creators | Fowler, Elizabeth Amy |
| Contributors | McIntosh, Robert ; Della Sala, Sergio ; Hart, Simon |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/25740 |
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