Goodman

Introduction

  • Different kinds of memory are mediated by dissociable neural systems.

  • Extinction learning involves suppressing a previously acquired memory in the absence of its original reinforcer.

  • Behavioral demonstration of extinction learning occurs when previously reinforced behavior declines, e.g., a rat stops running toward food when it's no longer provided.

Extinction Learning

  • Definition: Extinction is defined as learned suppression of a previously acquired memory (Bouton, 2004; Myers and Davis, 2007).

  • Extinction shows a response decrement in the behavior that was reinforced earlier.

  • Response decrement is the primary measure of extinction learning in studies.

Historical Perspectives on Extinction

Learning Theory Views

  • Stimulus-Response (S-R) View:

    • Proposed by Clark L. Hull, suggests initial memory acquisition is akin to a reflex, where stimuli activate automatic responses.

    • During extinction, stimuli elicit a "no response".

  • Cognitive View:

    • Championed by Tolman, states that animals learn meaningful relationships between stimuli, producing a cognitive expectation for reinforcement.

    • Extinction occurs when the expectation of reinforcement changes.

The Multiple Memory Systems Approach

  • Suggests distinct learning mechanisms coexist and contribute to extinction learning.

  • Recent maze learning experiments support the hypothesis of multiple memory systems in extinction.

Key Brain Structures in Extinction Learning

Hippocampus and Dorsal Striatum (DLS)

  • Hippocampus:

    • Mediates stimulus-stimulus associations.

    • Involvement in spatial learning and context-related memories.

  • Dorsal Striatum (DLS):

    • Mediates stimulus-response associations.

    • Activates learned behaviors without conscious expectation of reinforcement.

  • Findings show that both systems likely play different roles in extinction.

Experimental Paradigms in Studying Extinction

Two Types of Extinction Protocols

  1. Response Extinction Protocol:

    • Allows subjects to perform learned behavior without reinforcement.

    • Example: A rat runs to the goal but finds no food.

  2. Latent Extinction Protocol:

    • Prevents execution of the learned behavior.

    • Example: A rat is confined to the goal box without reinforcement, learning that the goal no longer contains food.

Evidence from Experiments

  • Both extinction protocols produce effective extinction learning, with different underlying mechanisms related to the involved neural systems:

    • DLS is necessary for response extinction; hippocampus is critical for latent extinction.

  • Contextual cues enhance latent extinction but have little effect on response extinction.

Effectiveness and Mechanisms of Extinction

Impact of Memory Type on Extinction

  • The effectiveness of extinction depends on whether the learned memory is cognitive or response-based.

  • Evidence indicates that response extinction is effective for DLS-dependent response memories, while latent extinction is more suited for hippocampal-dependent memories.

Implications for Understanding and Treatment of Psychopathologies

  • Extinction protocols may inform treatment approaches for maladaptive memories in disorders like PTSD, anxiety disorders, and addiction.

  • Understanding the specific neural and memory systems involved can guide therapeutic strategies.

Conclusion

  • The multiple memory systems framework is instrumental in understanding extinction.

  • Different extinction protocols engage distinct neural substrates resulting in unique extinction learning processes based on the type of memory involved.

  • Future treatment strategies can leverage these insights to address specific memory-related psychopathologies effectively.