The experiments presented in this thesis were based on the evidence of previous research that suggests that the memory functions dependent on the integrity of the hippocampus and frontal lobes, namely declarative and working memory respectively, are sensitive to the effects of corticosteroids (stress hormones). The first experiment investigated the effects of acute changes of three different levels of cortisol (high vs. control vs.low) and time of day (am vs. pm) on working memory and the episodic and semantic components of declarative memory. This was carried out using a singleblind, mixed (3 x 2) design with three groups of young, healthy males (N = 20 per group). Whilst significant differences in salivary cortisol levels were observed, the results failed to demonstrate any significant differences in any aspect of memory performance as a function of corticosteroids. However, whilst the results also failed to demonstrate significant differences in either aspect of memory performance as a function of time of day, they did identify a significant positive relationship between morning cortisol levels in the control group and two measures of episodic memory in the morning; this suggests that, in the morning, these aspects of memory performance were facilitated by higher cortisol levels. They also identified a significant negative relationship between afternoon cortisol levels in the high cortisol group and one measure of semantic memory in the afternoon; this suggests that, in the afternoon, this aspect of memory performance was impaired by higher cortisol. The second experiment investigated the effects of acute changes in corticosteroids following activation of the different corticosteroid receptors on working memory and the episodic and semantic components of declarative memory. This was carried out using a repeated measures design with nine patients with Addison's disease. The results suggest that, whilst significant effects were not identified across all memory tasks, activation of the mineraIocorticoids appears essential during sensory storage (i.e., encoding) whereas activation of the glucorticoids appears essential during memory consolidation and retrieval. This supports previous research carried out in rats (Oitzl & De Kloet, 1992). The results also suggest that balanced activation of the mineralocorticoids and glucocorticoids is necessary for optimal memory function. The contributions made by both experiments are discussed
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:251026 |
| Date | January 2002 |
| Creators | Tytherleigh, Michelle Yvette |
| Contributors | Rogers, Peter |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1983/645c28aa-de21-408e-931e-89cb8425ae7a |
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