Training procedures that eliminate conditioned fear in rodents and prevent fear relapse
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Training Procedures That eliminate Conditioned fear in Rodents and Prevent Fear Relapse. Brian L. Thomas, Ph.D. Baldwin-Wallace College Berea, Ohio USA. Conditioned Suppression in rats. Acquisition of fear in Context A Tone -> Foot Shock Extinction of fear in Context A or B

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

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

Brian L. Thomas, Ph.D.

Baldwin-Wallace College

Berea, Ohio USA


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


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


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


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


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).


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.


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.


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.


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.


Conclusions


Acknowledgments

  • Cheryl Novak, Associate Lab Director

  • David Revta, Technician

  • Drina Vurbic

  • Stephanie Damas

  • Marlo Cutler


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