Connectivity and plasticity of physiological mechanisms and temperament
Open Access
- Author:
- Mc Mahon, Elyse
- Graduate Program:
- Ecology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 23, 2022
- Committee Members:
- James Marden, Co-Chair of Committee
Sonia Cavigelli, Co-Chair & Dissertation Advisor
David Toews, Major Field Member
Margherita Cantorna, Outside Unit & Field Member
Jason Kaye, Program Head/Chair - Keywords:
- temperament
animal behavior
physiology
behavioral traits
glucocorticoids
physiological profiles - Abstract:
- Animal behaviour research has expanded over the past 20 years to study consistent individual differences in behaviour (i.e. temperament). These temperaments have been widely studied in relation to different ecological outcomes, such as fitness and survival. The underlying physiology of these traits may contribute to the relationships among fitness and temperament. My first chapter is a literature review that illustrates that there is limited information on causal relationships between physiology and temperament within individuals and hypothesizes physiological profiles for temperaments. My dissertation addresses questions about the interactions between temperament and the underlying physiology associated with temperament. Specifically, I answer the questions: 1) how temperament is characterized, 2) how the underlying physiology is related to temperament and 3) how flexible is the physiological profile and in turn, the associated temperaments. I used Sprague-Dawley rats in a laboratory setting to answer these questions to prevent external factors from altering these results. I first investigated how temperament is characterized. I conducted comprehensive and repeated behavior testing to compare two methodologies to identify temperaments that are individually-consistent across time and conditions. To measure single- and multi-behavior metrics of temperament, I measured rat behavior across five different arenas and repeated this at three time points. Certain single- and multi-behavior estimates of temperament were consistent across time and contexts than others; distance travelled/Activity along with Social Boldness, latency to interact with novelty and other Sociality- and Boldness-related behaviors were consistent across time and conditions, whereas Aggression and Exploration were less consistent. There was strong evidence that multiple behavioral estimates of temperament were more consistent over time or across conditions than single behaviors. Once I characterized different temperaments observed in Sprague-Dawley rats, I determined the underlying physiological profiles of each temperament. I measured HPA axis, innate immune system, adaptive immune system, gut microbiome and cardiac function and used correlation analysis to determine which physiological systems were associated with each temperament and used multiple linear regression to determine which physiological mechanisms predicted each temperament. Single-behavior metrics of temperament were more often correlated with physiological systems compared to multi-behavior metrics. Furthermore, HPA axis reactivity was predictive of multiple temperaments (both single- and multi-behavior metrics) while cardiac re/activity and HPA activity were significant predictors of some temperaments. The final step was to determine the flexibility of physiological profiles and their associated temperaments. In this study, I measured Exploration and Social Boldness along with all physiological mechanisms from the prior study in Chapter 3 and manipulated basal glucocorticoid (GC) levels. Animals in the GC treatment group had significantly increased basal GCs and latency to interact with novelty (lower Exploration) from before to during GC exposure, and significantly decreased stress-induced GCs, cell-mediated immune activity, and stress-induced heart rate compared to control rats. The Social Boldness temperament trait did not significantly change with GC treatment. This research provides the building blocks for future research to study the interactions between temperament and physiology. Once we understand how temperament and physiology interact, we can begin to understand how they influence individual differences in ecological outcomes.