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

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Conditioned Suppression in rats

• Acquisition of fear in Context A
• Tone -gt Foot Shock
• Extinction of fear in Context A or B
• Tone -gt No shock
• Tone -gt No shock and No Tone -gt Shock
• Test for relapse in Context A
• Tone -gt No Shock

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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

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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

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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

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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).

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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.

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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.

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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.

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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.

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Conclusions
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Acknowledgments

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