Source Paper
Memory for Extinction of Conditioned Fear Is Long-lasting and Persists Following Spontaneous Recovery
Learning & Memory • 2002
View Abstract
Conditioned fear responses to a tone paired with footshock rapidly extinguish when the tone is presented in the absence of the shock. Rather than erase conditioning, extinction is thought to involve the formation of new memory. In support of this, extinguished freezing spontaneously recovers with the passage of time. It is not known, however, how long extinction memory lasts or whether extinction interferes with consolidation of conditioning if given on the same day. To address this, we gave rats 7 trials of auditory fear conditioning followed 1 h later by 20 extinction trials, and tested for spontaneous recovery after a delay of 0, 1, 2, 4, 6, 10, or 14 d. Conditioned freezing to the tone gradually recovered with time to reach 100% by day 10. No-extinction controls indicated that the increase in freezing with time was not owing to incubation of conditioning memory. Complete spontaneous recovery indicates that extinction training given 1 h after conditioning does not interfere with the consolidation of conditioning memory. Despite complete recovery of freezing, rats showed savings in their rate of re-extinction, indicating persistence of extinction memory. These data support the idea that conditioning and extinction of fear are learned by independent systems, each able to retain a long-term memory.
Extinction Training
Objective: To assess extinction memory formation and persistence by measuring spontaneous recovery of conditioned fear following extinction training, and to determine whether extinction training interferes with conditioning consolidation when given on the same day
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Protocol Steps
Auditory Fear Conditioning
Rats received 7 trials of auditory fear conditioning pairing tone with footshock
Note: Initial conditioning phase
View evidence from paper
“gave rats 7 trials of auditory fear conditioning followed 1 h later by 20 extinction trials”
Extinction Training
Rats received 20 extinction trials consisting of tone presentations without footshock
Note: Extinction trials assess extinction memory formation without reinforcement
View evidence from paper
“20 extinction trials, and tested for spontaneous recovery after a delay of 0, 1, 2, 4, 6, 10, or 14 d”
Spontaneous Recovery Testing
Rats were tested for spontaneous recovery of conditioned freezing to the tone at multiple time points following extinction training
Note: Multiple delay intervals used to assess time-dependent recovery of conditioned fear
View evidence from paper
“tested for spontaneous recovery after a delay of 0, 1, 2, 4, 6, 10, or 14 d”
