title: Sexually divergent expression of active and passive conditioned fear responses in rats.
abstract: Traditional rodent models of Pavlovian fear conditioning assess the strength of learning by quantifying freezing responses. However, sole reliance on this measure includes the de facto assumption that any locomotor activity reflects an absence of fear. Consequently, alternative expressions of associative learning are rarely considered. Here we identify a novel, active fear response ('darting') that occurs primarily in female rats. In females, darting exhibits the characteristics of a learned fear behavior, appearing during the CS period as conditioning proceeds and disappearing from the CS period during extinction. This finding motivates a reinterpretation of rodent fear conditioning studies, particularly in females, and it suggests that conditioned fear behavior is more diverse than previously appreciated. Moreover, rats that darted during initial fear conditioning exhibited lower freezing during the second day of extinction testing, suggesting that females employ distinct and adaptive fear response strategies that improve long-term outcomes.
authors.affiliation: Department of Psychology, Northeastern University, Boston, United States.
authors.forename: Tina M
authors.initials: TM
authors.lastname: Gruene
authors.affiliation: Department of Psychology, Northeastern University, Boston, United States.
authors.forename: Katelyn
authors.initials: K
authors.lastname: Flick
authors.affiliation: Department of Psychology, Northeastern University, Boston, United States.
authors.forename: Alexis
authors.initials: A
authors.lastname: Stefano
authors.affiliation: Cold Spring Harbor Laboratories, Cold Spring Harbor, United States.
authors.forename: Stephen D
authors.identifier: http://orcid.org/0000-0001-6927-0189
authors.initials: SD
authors.lastname: Shea
authors.affiliation: Department of Psychology, Northeastern University, Boston, United States.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Shansky
mesh_terms: D000818:Animals; D003214:Conditioning, Classical; D005239:Fear; D005260:Female; D008124:Locomotion; D008297:Male; D017207:Rats, Sprague-Dawley
keywords: active responses; fear conditioning; neuroscience; rat; sex differences