Training Procedures That eliminate Conditioned fear in Rodents and Prevent Fear Relapse

1. Training Procedures That eliminate Conditioned fear in Rodents and Prevent Fear Relapse Brian L. Thomas, Ph.D. Baldwin-Wallace College Berea, Ohio USA

2. Conditioned Suppression in rats • Acquisition of fear in Context A • Tone -> Foot Shock • Extinction of fear in Context A or B • Tone -> No shock • Tone -> No shock and No Tone -> Shock • Test for relapse in Context A • Tone -> No Shock

3. Conventional Extinction of fear • Nonreinforcement of CS alone • Allows for spontaneous recovery of fear after a retention interval • Allows for renewal of fear outside of the extinction setting • Allows for reinstatement of fear after re-exposure to the US • Allows fear to relapse

4. Explicitly unpaired (EU) extinction • Nonreinforcement of CS alone plus unsignaled USs • Prevents spontaneous recovery of fear after a retention interval • Prevents renewal of fear outside of the extinction setting • Prevents reinstatement of fear after re-exposure to the US • Prevents fear relapse

5. Importance of shock intensity • How does the intensity of the shock given during EU extinction affect extinction and relapse? • All rats received pairings of the CS with a 0.06 mA shock during Acquisition. • During Extinction: • Group EU received 4 CSs intermingled with 2 USs at 0.6 mA • Group EU/D received 4 CSs intermingled with 2 USs at 0.2 mA • Group EU/I received 4 CSs intermingled with 2 USs at 1.0 mA • Group E/B received 4 CSs • Group FC did not receive and CSs or USs

7. Importance of Number of shocks • How does the number of shocks per extinction session affect extinction and relapse? • Every extinction session had 4 nonreinforced CSs. • The number of shocks per session varied between groups (1, 2 or 4) • Shocks were either intermingled (EU) or given after the 4th CS (CU).

9. Importance of Context • What role do contextual stimuli play in EU extinction? • Experiment 1: • Group EU received 4 CSs and 2 USs intermingled during the same session. • Group E-U received 4 CSs and 2 USs during separate, alternating sessions in the same context. • Group E/U received 4 CSs and 2 USs during separate, alternating sessions and CSs were delivered in a different context from USs.

11. Importance of Context • What role do contextual stimuli play in EU extinction? • Experiment 2: • Group EU/PreB received preexposure to the extinction context prior to EU extinction. • Group EU/PreC received preexposure to a non-extinction context prior to EU extinction. • Group EU/HC remained in their home cages during the Preexposure phase.

13. Importance of US specificity • Does the US provided during EU extinction have to be the US that caused fear acquisition? • Group EU/SS received a shock US during Acquisition and Extinction. • Group EU/SN received a shock US during Acquisition and a loud noise US during Extinction.

15. Summary of findings • EU extinction prevented the relapse of fear most effectively when: • The US provided during extinction was at least as intense as the US experienced during fear acquisition. • The US provided during extinction was intermingled among the CSs and at least 2 USs were given in each extinction session. • The USs provided during extinction were presented in the same context as the CSs. • The subject had not received exposure to the extinction context prior to the Extinction phase. • When the US provided during extinction was either a foot shock or a loud noise.

16. Conclusions

17. Acknowledgments • Cheryl Novak, Associate Lab Director • David Revta, Technician • Drina Vurbic • Stephanie Damas • Marlo Cutler