Individual differences predict susceptibility to conditioned fear arising from psychosocial trauma.
BACKGROUND
Classical Pavlovian fear conditioning has been widely used in preclinical studies to gain insights into anxiety-related disorders. In this study we examined whether pre-existing behavioral differences, and/or behavioral differences displayed during fear induction, predict the severity of the conditioned fear response that can develop after an episode of psychosocial conflict.


METHODS
Prior to conditioning, male rats (intruders) were behaviorally assessed using the novel environment exploration and defensive burying tests. These animals were subsequently placed in the territory of an older male (resident) that invariably attacked the intruder.


RESULTS
Upon return to this territory 24 h later, intruders moved less than controls and produced more distress vocalizations, indicating conditioned fear to context. Additionally, analyses revealed that both pre-existing behavioral differences, and the animal's response during social conflict, predicted the magnitude of the subsequent conditioned fear response. Specifically, animals that engaged in higher levels of novel environment exploration, that exhibited a greater number of defensive burying behaviors, and that demonstrated higher levels of fighting and guarding during social conflict, displayed less evidence of conditioned fear.


CONCLUSIONS
These findings show that the behavioral variability existent within a normal outbred population can predict the magnitude of the conditioned fear response.
Walker
Frederick R
FR
Laboratory of Brain and Behaviour, University of Newcastle, NSW 2308, Australia. rohan.walker@newcastle.edu.au <rohan.walker@newcastle.edu.au>
Hinwood
Madeleine
M
Masters
Louise
L
Deilenberg
Robert A
RA
Day
Trevor A
TA
D000818:Animals; D001143:Arousal / Q000502:physiology; D001245:Association Learning / Q000502:physiology; D001362:Avoidance Learning / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology*; D002940:Circadian Rhythm; D003214:Conditioning, Classical / Q000502:physiology*; D003220:Conflict, Psychological; D004195:Disease Models, Animal; D004924:Escape Reaction / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology; D005239:Fear / Q000502:physiology* / Q000523:psychology; D046352:Freezing Reaction, Cataleptic; D006702:Homing Behavior / Q000502:physiology; D007206:Individuality; D008297:Male; D011336:Probability; D051381:Rats; D017207:Rats, Sprague-Dawley; D012919:Social Behavior; D013313:Stress Disorders, Post-Traumatic / Q000503:physiopathology* / Q000523:psychology; D014828:Vocalization, Animal / Q000502:physiology