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. Author manuscript; available in PMC: 2014 Jun 1.
Published in final edited form as: Biol Psychiatry. 2012 Dec 13;73(11):1071–1077. doi: 10.1016/j.biopsych.2012.10.021

Figure 2.

Figure 2

Paired VNS accelerates extinction of conditioned fear. (A) Percent of conditioned freezing in rats given repeated extinction trials. Tests measuring freezing, and VNS or sham treatment were given on alternate days. Paired VNS overlapped with exposure to conditioned cues. Unpaired VNS was given in the home cage, immediately after extinction training. Because testing days involved exposure to the conditioned tone without footshock, extinction learning could develop over all 11 days. Paired VNS rats reached a point of remission of fear expression (< 10 % of CFR) whereas unpaired- and sham-treated rats did not (* p<.05 Paired vs. Unpaired; ** p<.05 Paired vs. Unpaired and Sham). (B) Spontaneous recovery of fear was examined in 4 Sham and 9 VNS rats 2 weeks after Test 5 (Day 11). After the passage of 2 weeks, freezing levels remained unchanged in both sham and VNS rats indicating that spontaneous recovery of fear did not occur in either group.