Learning in the company of individuals with similar phenotypes can facilitate fear extinction in rats selectively bred for their locomotor response to novelty
Prater KE, Aurbach EL, Larcinese H, Blandino P Jr, Watson SJ, Maren S, Akil H
Society for Neuroscience. 2015.
As we search for new treatments for anxiety disorders, it is important to understand why certain individuals are more vulnerable to developing PTSD after a traumatic event and how we can help vulnerable individuals improve their prognosis. We believe that our rat model of individual differences in locomotor response to a novel environment provides insight into vulnerability and resilience to anxiety disorders. In experiment one, rats selectively bred for high (bHR) or low (bLR) locomotor response to a novel environment and rats from the F1 generation of a bHR-bLR cross (bIRs), which display an intermediate locomotor phenotype, received a standard fear conditioning and extinction paradigm. bLRs demonstrated decreased extinction learning and extinction retention compared to bIRs and bHRs, while bHRs exhibited faster extinction and greater retention than bIRs. This indicates that bLRs, like PTSD patients, may be vulnerable to maladaptive fear behaviors, while bHRs may be more resilient. In a second study, it was found that although bLR extinction learning remains deficient compared to bHRs, grouping animals solely with their in-group phenotype during fear conditioning and extinction results in increased extinction learning compared with animals trained in isolated pairs or mixed phenotypes. We are replicating these findings, and studying the neural correlates underlying these differences in extinction learning. These results may have significant implications for the study of fear behavior in animals and humans, as individual differences in temperament may significantly impact fear extinction learning.