Abstract:
Animals must extract information from their environment to make adaptive behavioral decisions when confronted with such things as social challenge. Previous studies have uncovered how different sources of information affect contest dynamics, however, relatively little is understood about how the brain processes all sorts of different information and translates this information into diverse behavioral responses. My overarching goals were to investigate behavioral responses to several types of social information, including intrinsic information (e.g., sex, body size) and extrinsic information (e.g., contest outcomes), and then probe potential neural mechanisms underlying these adaptive behavioral changes. First, I discovered that males and hermaphrodites possess distinct baseline hormone profiles, and used different fighting strategies against a same-sex opponent, which might be associated with different endocrine responses to social challenge. I also discovered that, during a contest, individual standard length and how an individual perceives its opponent’s size likely contributes to contest dynamics. These results revealed that the contest decisions of rivulus are mediated by various sources of information. I further demonstrated that the different levels of information (e.g., morphological trait vs. behavioral traits vs. morphological + behavioral traits) elicited different levels of aggression as well as unique pattern of immediate early gene expression in the preoptic area, amygdala and hippocampus, suggesting a role for these brain nuclei in modulating behavioral responses to the stimuli, and perhaps future behavioral performance. Finally, I demonstrated that single winning or losing experiences had a significant influence on aggression and cognitive abilities, and activated distinct patterns of protein expression in forebrain, suggesting that functional differences arise in the brains of winners and losers with implications for modulating aggression and learning behavior. In conclusion, my dissertation highlights the importance of various types of information on rivulus’ contest dynamics, and revealed potential neural mechanisms underlying experience-induced changes in behavior. Together, the studies presented here establish a foundation on which future investigations can be built to better understand how divergent social experiences sculpt the brain in ways that lead to particular, experience-induced behavioral phenotypes.
