Mapping fear behavior

Abstract

The ability to appropriately respond to threats is critical for survival. Disruptions in the neural circuits underlying threat responding are studied in animal models and have clinical implications for anxiety disorders in humans. Pavlovian fear conditioning has been extensively used to study the behavioral and neural basis of defensive systems for threat in animals. In a typical procedure, a cue is paired with foot shock, and subsequent cue presentation elicits freezing, a behavior linked to predator detection. Studies have since shown a fear conditioned cue can elicit locomotion, a behavior that - in addition to jumping, and rearing - is linked to imminent or occurring predation. Yet, the full neural circuit for conditioned, activity-promoting behaviors (e.g. locomotion, jumping, and rearing) remains unclear. The overarching goal of this dissertation is to demonstrate that a fear conditioned cue elicits a variety of defensive behaviors and to probe the neural circuit responsible for the expression of such activity-promoting defensive behaviors. To address the lack of research on activity-promoting defensive behaviors, I conducted experiments to observe multiple behaviors during fear discrimination over a baseline of reward seeking and constructed temporal ethograms of behavior. To improve efficiency in behavior scoring for future projects, I devised and trained a machine learning pipeline using convolutional neural networks. To aid in the understanding of the full neural circuit for activity-promoting defensive behaviors, I investigated the role of dopaminergic neurons of the ventral tegmental area in the expression of the defensive behaviors we observed during fear discrimination. Ultimately, the findings in this dissertation contribute to our general understanding of fear behavior in animals and may inform therapeutic strategies for anxiety disorders.