Pavlovian Conditioned Flight Responses in Rats are Conditioned by Threatening Contexts

Abstract

Humans and animals use environmental cues to determine appropriate defensive responses. Understanding the mechanisms of context-mediated fear responses is crucial, as the dysregulation of these processes are central to trauma and stress-related disorders (such as anxiety or post-traumatic stress disorder). Decades of research establish how context mediates conditioned freezing in rats, but little literature has explained the mechanisms behind flight. To address this, we used a modified Pavlovian conditioning procedure in which the standard conditioned stimulus is replaced by a serial-compound stimulus (SCS) comprised of a pure tone followed by white noise. Rodents display freezing to the tone and flight to the white noise in this paradigm. Interestingly, flight is only observed in the conditioning context. Here, we conducted two experiments to further investigate how flight responses are contextually gated. 1) Conditioned animals were placed into a novel context where one group of animals received unsignaled footshocks (Shock) and one group did not receive footshocks (No-Shock). The next day both groups were returned to this context and underwent SCS-alone presentations. Animals that received unsignaled footshock displayed robust flight responses, whereas No-Shock animals did not. 2) Conditioned animals either underwent fear extinction of the conditioning context by exposing the rats to the context for 45 min (Ext) or were exposed to a novel context for the same period of time (No Ext). The next day both groups were presented SCS-alone trials in the conditioning context. No-Ext rats still displayed robust flight responses to the SCS, whereas Ext animals did not. Collectively, these two results demonstrate that the contextual gating of flight behavior in rats in driven by context fear and suggest that flight is driven by a high fear state combining auditory and environmental fear. Understanding how context regulates fear responses is vital to improving current trauma and stress-related therapies.