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. Author manuscript; available in PMC: 2020 Jan 1.
Published in final edited form as: Brain Stimul. 2018 Sep 21;12(1):9–18. doi: 10.1016/j.brs.2018.09.013

Figure 4. Separating conditioning of CS1 and CS2 by context blocks the VNS+Extinction effect on generalization. A. Timeline for AFC, CFRT, and extinction treatment.

Figure 4.

AFC was administered across two days, where CS1 was presented only in Context A, and CS2 was presented only in Context C, but both CS1 and CS2 were presented during the same session. Twenty-four hours after AFC, a Pre-Extinction CFRT was administered for CS1 in Context A, where CS1 was presented four times without reinforcement. On the same day, a Pre-Extinction CFRT was also administered to CS2 in Context C, where CS2 was presented four times without reinforcement. Following the Pre-Extinction CFRT day, rats were subjected to extinction treatment consisting of either: 20 presentations of CS1 in Context A paired with sham stimulation (Extended Extinction), or 4 presentations of CS1 in Context A paired with VNS (VNS+Extinction). Twenty-four hours following extinction, a Post-Extinction CFRT was given to CS1 in Context A, and then on the same day a Post-Extinction CFRT was given for CS2 in Context C. B. Extended Extinction and VNS+Extinction rats show equal reduction in conditioned fear to the Presented CS. Following extinction of CS1 in Context A, Extended Extinction and VNS+Extinction rats showed reduced conditioned fear to the Presented CS versus Pre-Extinction (p=2.3×10−3) and (p=1.2×10−3), respectively. C. Neither Extended Extinction rats or VNS+Extinction rats show reduced freezing to the Non-Presented CS. Freezing to the Non-Presented CS was not reduced after Extinction training for Extended Extinction rats (p=0.38). Similar to Figure 2, freezing to the Non-Presented CS was also not reduced for VNS+Extinction rats versus Pre-Extinction (p=0.40). D. Baseline freezing to the extinction context is not different between groups. Extended Extinction and VNS+Extinction rats spent an equal amount of time freezing to the extinction context during the five minutes prior to presentation of CS1 during the Post-Extinction CFRT (p=0.53). E. Baseline freezing to the non-extinction context is not different between groups. Extended Extinction and VNS+Extinction rats spent an equal amount of time freezing to the non-extinction context during the five minutes prior to CS2 presentation during the Post-Extinction CFRT (p=0.62).