| dc.description.abstract | Decades of neuroscience research has established the modulating role of stress in cognitive function, such as learning and memory, namely from severe stressors that invoke fear or physical stress. The effect on cognition from other types of stressors, such as stress stemming from social position, has yet to be understood and has received limited attention. Evidence stemming from the graded relationship of socioeconomic status on health outcomes, suggest one’s relative social position may have adverse physiological consequences. Therefore, we used a simple rodent model to examine the relationship between social position on cognitive functions. This thesis aimed to 1) determine whether social hierarchy in rats could be reliably measured using the Tube Test, 2) examine whether social position mediates spatial learning and memory, and 3) assess the role of sex in the relationship between social position, spatial learning, and memory.
Eighty adult, male and female Sprague-Dawley rats were grouped, with either 4 males, or 4 females per group (N = 40 / sex). The Tube Test was conducted to determine the social position of groups over 3 days by examining pairwise dominance interactions. Afterwards, Morris Water Maze training was used to assess spatial learning over 4 days, memory through the probe test, and behavioural flexibility over 2 days of reversal training. Subsequently, a one-day Tube Test was conducted to examine the stability of the social positions. Following the completion of behavioral testing, body weight, and stress-sensitive organ weights (adrenal and thymus glands) were measured. The findings of our study provide no evidence that social position affects cognitive function as spatial learning, reversal learning and memory performance was not significantly different across social positions. We found no sex differences in relationship between social position and spatial performance, and our study found no differences in body weight and in stress-sensitive organs (adrenal and thymus glands) across social positions in male and female rats.
In summary, our results suggest no evidence that social position within a group of same-sex housed rats altered learning and memory performance. Furthermore, we did not find sex differences in the relationship between social position and cognition. In our study, animals were not subjected to known socially stressful conditions such as social isolation or overcrowding, and were left alone to examine the social stress from natural occurring social stratification. Further research is needed to confirm our findings and explore when social position becomes a stressor. Furthermore, future directions can aim to explore the neurobiological mechanisms from social stress by comparing corticosterone levels and target proteins (e.g., AMPA receptors) across social positions. | en |
