Visual working memory, a limited temporary storage system for relevant information, is a critical contributor to many essential cognitive functions. In this thesis, I aimed to investigate some of the mechanisms underlying working memory in healthy humans and neurological patients, as well as its modulation by processes attributed to attention and the neurotransmitter dopamine. There currently is an important controversy regarding models of working memory. I investigated whether a resource model of memory (which argues for a limited resource distributed amongst to-be-remembered items) might be extended to the domain of visual motion. The results suggest that this is indeed be the case, supporting the utility of this model as a general conceptual framework for understanding working memory across a range of visual features and modes of presentation (Chapter 2). A comprehensive model of working memory should consider its relationship with attention. My findings point to an intimate yet highly specific relationship between these two processes, demonstrating that attention is essential for maintenance of integrated features within working memory (Chapters 2 and 4). Further, evidence for a causal role of early visual areas in maintenance of items in focus of attention, compared to the full content of working memory, is provided using transcranial magnetic stimulation (Chapter 3). Finally, I investigated neuromodulation of working memory processes by dopamine in patients with dopamine dysfunction (Parkinson’s disease) and using the dopamine agonist, Cabergoline, in healthy controls. The results demonstrate that dopamine can modulate working memory precision (Chapter 5 and 6). Furthermore, deficits in working memory were also observed in individuals with glucocerebrosidase mutations who have a significantly raised risk of developing Parkinson’s disease (Chapter 7). I discuss the possibility that specific deficits in working memory might provide a cognitive marker of risk for neurodegeneration and development of Parkinson’s disease.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626168 |
| Date | January 2013 |
| Creators | Zokaei, N. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1393276/ |
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