Date of Award

2011

Degree Type

Thesis

Department

Psychology

First Advisor

Hammonds, Mike

Subject Headings

Hippocampus (Brain), Depression, Mental, hippocampus, depression, exercise, neurogenesis, environmental enrichment

Abstract

The hippocampus provides negative feedback for the Hypothalamic-Pituitary- Adrenal (HPA) axis. The HPA axis is responsible for producing a response to stressful stimuli. The hippocampus is sensitive to high levels of glucocorticoids (GCs), because of its large number of GC receptors. In times of severe stress, hippocampal function is inhibited and its control over the HPA axis is diminished, leading to hyperactivity of the adrenal glands as well as hypercortisolism, typical of depression. Long-term stress and depression can eventually lead to chronic impairments in cognitive ability, as well as structural damage in the hippocampus. Exercise and environmental enrichment stimulate significant growth and activity in the hippocampus, and have been used successfully as antidepressant treatments in previous studies. However, these previous studies failed to demonstrate whether such treatments are capable of preventing the cognitive symptoms of depression during times of persistent chronic prolonged stress. Previous research has also evaded the possibility of a potential additive effect when both treatments are used in combination. The current study aims to extend previous research in this area by examining both the possibility of a preventative efficacy of hippocampal stimulation during periods of stress, as well the possibility of an additive effect associated with the use of both treatments. Rodents went through a 10-week period of CMS along with concurrent exposure to environmental enrichment, environmental enrichment and exercise, or neither. Sucrose consumption was used as a measure of anhedonia at the 8-week point. At the completion of the 10 week CMS period, spatial memory was measured using the Morris Water Maze and a Novel Object Placement Task. The overall level of spatial memory impairment was determined based on the group means collected during these tests. Overall, results from the current study provide evidence supporting the preventative efficacy of hippocampal stimulation during periods of stress. Whil

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