Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Psychology

Program Name/Specialization

Behavioural Neuroscience

Faculty/School

Faculty of Science

First Advisor

Diano F. Marrone

Advisor Role

Primary Advisory

Abstract

Normal ageing is associated with significant changes in cognitive function, including the decline of some forms of memory. The hippocampal formation is critical to learning and memory function, and plasticity in this region declines with age. Additionally, age-related differences in plasticity are greatest at lower levels of stimulation, thus peri-threshold plasticity may be of the greatest relevance for age-related changes in cognition. Moreover, the hippocampus is prone to changes in the expression of gene products that mediate plasticity with age. The current thesis attempts to link these observations by measuring hippocampal expression of Arc, an immediate-early gene that is critical for both plasticity and memory function, using a behavioural analogue of minimal stimulation. In this paradigm, adult (11 months) and aged (23 months) F344 rats traversed a varying number of laps (i.e., 1, 3, or 5) in a triangular track. To test cholinergic influences on these dynamics, animals were also injected with physostigmine, a cholinergic agonist, which has been shown to modulate hippocampal physiology. Consistent with previous studies, a greater number of laps induced Arc in more cells across the hippocampus. In addition, age altered the Arc expression that followed different stimulation levels, but not in the way hypothesized. Aged animals, in fact, expressed more Arc following fewer laps. Additionally, we did not show any evidence of one-trial learning as has previously been demonstrated. Finally, physostigmine administration significantly increased cellular recruitment selectively in the dorsal regions of the hippocampus. These data suggest that age-related changes in neural activation are present, but complex. Additionally, these data show that physostigmine appears to augment IEG dynamics.

Convocation Year

2016

Convocation Season

Spring

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