Date of Completion
During aging, hippocampal functioning is impaired; specifically aged humans and rats show reduced performance on spatial memory tasks. An age-related reduction in the neurotransmitter acetylcholine has been postulated to underlie this impairment. Rhythmic oscillations (theta, gamma) may serve to synchronize activity within the hippocampus and across the brain during learning; these may also change with aging.
To determine what aspects of oscillation are important for memory processing, the effects of aging, encountering a novel situation, learning a new task and cholinergic system activation (with physostigmine) were examined. Both age groups showed increased theta, but not gamma activity when encoding a novel situation. Activating the cholinergic system shifted theta power to a lower frequency with no effect on gamma. These results indicate a more prominent role for theta than gamma in processing new spatial information.
In addition, a behavioral paradigm to study changes in hippocampal theta and gamma over trials during single-day learning of a place or response task was designed. Pilot data demonstrates that rats are capable of learning these tasks within a single day, and that hippocampal theta and gamma increase with maze running in a familiar situation, with no difference over trials on a simple-alternation task. Theta power is expected to show more of a decrease over trials during response than place learning.
Howe, Matthew D., "Hippocampal Theta and Gamma: Effects of Aging, Environmental Change, Cholinergic Activation and Learning" (2012). Honors Scholar Theses. Paper 272.