The Fragrant Power of Collective Fear

<div><p>Fear is a well-characterized biological response to threatening or stressful situations in humans and other social animals. Importantly, fearful stimuli in the natural environment are likely to be encountered concurrently by a group of animals. The modulation of fear acquisition and fear memory by a group as opposed to an individual experience, however, remains largely unknown. Here, we demonstrate a robust reduction in fear memory to an aversive event undertaken in a group despite similar fear learning between individually- and group-conditioned rats. This reduction persists outside the group confines, appears to be a direct outcome of group cognizance and is counteracted by loss of olfactory signaling among the group members. These results show that a group experience of fear can be protective and suggest that distinct neural pathways from those classically studied in individuals modulate collective fear memories.</p></div

Simplified punch and diemoking/ Walker

xii, 235 hal.: ind.; 22 cm

Simplified punch and diemaking/ Walker

xii, 235 hal.: ind.; 22 cm

Group-induced fear reduction is dependent on the co-presence of cagemates during conditioning but not testing.

<p>(A) Schematic for group testing. Individual and Group rats are fear-conditioned with 1 CS-US pair as described. Twenty-four hours later, the rats are exposed to a LTM test in group with their cagemates and their freezing scores are determined manually. (B) Individual and Group rats maintained respective similar levels of freezing during a LTM test whether they were tested individually or in group. Two-way ANOVA revealed an effect of conditioning (Individual or Group), F (1, 68) = 16.89, p<0.001, but not testing (individually or in group), F (1, 68) = 1.63, p>0.1, or an interaction (conditioning x testing), F (1, 68) = 1.34, p>0.1. Data presented as mean + sem.</p

Group conditioning causes a robust reduction in subsequent fear expression.

<p>(A) Schematic: rats are divided between Individual and Group conditions. After a 10-min period, a transparent insert is placed and rats are assigned to 1 of 3 compartments. A single or three tones (CS) co-terminating with a footshock (US) are delivered. Twenty-four hours later, the rats are exposed to three CS presentations in a different context for LTM testing. (B) Group rats freeze significantly less than Individuals during CS presentation while maintaining similar low levels of Pre-CS baseline (BL) freezing. Two-way Repeated Measures (RM) ANOVA revealed an effect of condition (Individual or Group), F (1, 34) = 8.93, p<0.01, and an interaction (BL x CS [average of 3]), F (1, 34) = 6.12, p<0.05. Post-hoc tests revealed no differences for BL, p>0.1, and a robust reduction in Group CS freezing, p<0.001. This was replicated in a LTM test for 3 CS-US deliveries during conditioning. Two-way RM ANOVA revealed an effect of condition, F (1, 31) = 5.05, p<0.05, and an interaction, F (1, 31) = 4.17, p<0.05. Post-hoc tests revealed no differences for BL, p>0.1, and a significant reduction in Group CS freezing, p<0.01. Data presented as mean + sem.</p

Olfactory signals among Group rats play a significant role in mediating conditioned fear reduction.

<p>(A) Schematic for zinc sulfate-induced peripheral anosmia. Rats are subjected to a buried food test. Seventy-two hours later, the rats undergo zinc-sulfate induced peripheral anosmia or sham procedure and the buried food test is repeated the following day to ensure intervention success. Twenty-four hours later, the rats are randomly assigned to Individual or Group conditioning. (B) Zinc sulfate induced peripheral anosmia that was characterized by >10 min latency on the buried food test in both Individual and Group rats. All rats displayed similar baseline pre-treatment latencies which were also similar to sham Individual and Group rat latencies; two way ANOVA, p>0.1. (C) Group rats with peripheral anosmia displayed freezing levels similar to those in Individual anosmic rats while sham Group rats maintained the fear reduction in comparison to sham Individual rats in a LTM test. Two-way ANOVA revealed an effect of conditioning (Individual or Group), F (1, 29) = 9.28, p<0.01. Post-hoc tests revealed that this difference was exclusively driven by the sham rats (Individual vs Group), p<0.05, but not anosmic rats (Individual vs Group), p>0.1. Data presented as mean + sem.</p