Functional magnetic resonance imaging of recovery from post-stroke aphasia

Bethel, Susannah (2009) Functional magnetic resonance imaging of recovery from post-stroke aphasia. PhD thesis, University of Nottingham.

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This thesis presents the design, development and application of a novel overt picture-naming paradigm through a series of exploratory behavioural and imaging experiments. The paradigm is subsequently used in a functional magnetic resonance imaging study of recovery from post-stroke aphasia. The possibility of comparing correct and error naming responses in aphasic patients and unimpaired subjects induced to make errors was investigated and successfully trialled. This research improves on techniques currently favoured in imaging studies to explore the processes involved in functional recovery in a more analytical way. The novel study design provides a new way to interrogate processing involved in the production of aphasic responses.

The intentions of this project were to drive the research field of post-stroke aphasia recovery forward by suggesting and applying new methods of using functional imaging to investigate the current pertinent research questions. In addition to this, it was aimed that data collected from participants who have an aphasic deficit, and those with a healthy language system, would be analysed to provide evidence of how a stroke damaged brain may recover functional language. It was hypothesised that results from aphasic patients would show that successful language performance is associated with cortical activation of the patients' normal left hemispheric language areas, around their lesion site. Conversely, the hypotheses state that production of linguistic errors would correlate with an increase in activation in areas of the right hemisphere homologous to the left lateralised fronto-temporal language production network. It was thought that further investigation of successful and unsuccessful language performance in unimpaired speakers would echo this finding.

The current debate in this research field centres on the role of the undamaged hemisphere in successful recovery. Five chronic stage aphasics were tested using the developed continuous scanning, event-related paradigm and their correct and error naming trials were compared. Results indicate that recruitment of cortical areas homologous to the stroke lesion can support successful language processing. This is contrary to the theory that disinhibition of non-dominant language areas may contribute to the production of aphasic errors.

An investigation of forced errors in unimpaired speakers was also conducted to provide comparisons with the aphasic patient group. Imaging results showed that the naming-to-deadline paradigm used may provide a useful baseline for the normal processes involved in the monitoring and control of task performance.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Sunderland, A.
Keywords: Complications of cerebrovascular disease, Magnetic resonance imaging, Aphasic responses, Functional recovery
Subjects: W Medicine and related subjects (NLM Classification) > WL Nervous system
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Clinical Sciences
Item ID: 12635
Depositing User: EP, Services
Date Deposited: 08 Jun 2012 10:17
Last Modified: 17 Dec 2017 00:51

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