title: Changes in heart rate variability are associated with expression of short-term and long-term contextual and cued fear memories.
abstract: Heart physiology is a highly useful indicator for measuring not only physical states, but also emotional changes in animals. Yet changes of heart rate variability during fear conditioning have not been systematically studied in mice. Here, we investigated changes in heart rate and heart rate variability in both short-term and long-term contextual and cued fear conditioning. We found that while fear conditioning could increase heart rate, the most significant change was the reduction in heart rate variability which could be further divided into two distinct stages: a highly rhythmic phase (stage-I) and a more variable phase (stage-II). We showed that the time duration of the stage-I rhythmic phase were sensitive enough to reflect the transition from short-term to long-term fear memories. Moreover, it could also detect fear extinction effect during the repeated tone recall. These results suggest that heart rate variability is a valuable physiological indicator for sensitively measuring the consolidation and expression of fear memories in mice.
authors.affiliation: Key Laboratory of Brain Functional Genomics (Ministry of Education), Institute of Brain Functional Genomics, East China Normal University, Shanghai, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Hui
authors.initials: H
authors.lastname: Kuang
authors.forename: Fang
authors.initials: F
authors.lastname: Zhao
authors.forename: Joe Z
authors.initials: JZ
authors.lastname: Tsien
mesh_terms: D000818:Animals; D001307:Auditory Perception / Q000502:physiology; D001522:Behavior, Animal; D003213:Conditioning, Psychological / Q000502:physiology; D003463:Cues; D004562:Electrocardiography; D005239:Fear / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D057567:Memory, Long-Term / Q000502:physiology*; D008570:Memory, Short-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL