Source Paper
The Role of Ventromedial Prefrontal Cortex in the Recovery of Extinguished Fear
Gregory J. Quirk, Gregory K. Russo, Jill L. Barron, Kelimer Lebron
Journal of Neuroscience • 2000
View Abstract
Conditioned fear responses to a tone paired with footshock extinguish when the tone is presented repeatedly in the absence of shock. Rather than erase the tone-shock association, extinction is thought to involve new learning accompanied by inhibition of conditioned responding. Despite much interest in extinction from a clinical perspective, little is known about the neural circuits that are involved. Although the prefrontal cortex has a well established role in the inhibition of inappropriate behaviors, previous reports have disagreed as to the role of the ventromedial prefrontal cortex (vmPFC) in extinction. We have reexamined the effects of electrolytic vmPFC lesions made before training on the acquisition, extinction, and recovery of conditioned fear responses in a 2 d experiment. On Day 1 vmPFC lesions had no effect on acquisition or extinction of conditioned freezing and suppression of bar pressing. On Day 2 sham rats recovered only 27% of their acquired freezing, whereas vmPFC-lesioned rats recovered 86%, which was indistinguishable from a control group that never received extinction. The high recovery in lesioned rats could not be attributed to decreased motivation or altered sensitivity to footshock. vmPFC lesions that spared the caudal infralimbic (IL) nucleus had no effect. Thus, the vmPFC (particularly the IL nucleus) is not necessary for expression of extinction, but it is necessary for the recall of extinction learning after a long delay. These data suggest a role of the vmPFC in consolidation of extinction learning or the recall of contexts in which extinction took place.
Electrolytic vmPFC Lesions
Objective: To assess the effects of electrolytic ventromedial prefrontal cortex (vmPFC) lesions made before training on the acquisition, extinction, and recovery of conditioned fear responses
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Protocol Steps
Electrolytic vmPFC Lesion Surgery
Perform electrolytic lesions of the ventromedial prefrontal cortex before training begins
Note: Lesions made before training to assess effects on fear conditioning and extinction learning
View evidence from paper
“electrolytic vmPFC lesions made before training on the acquisition, extinction, and recovery of conditioned fear responses”
Day 1 - Acquisition and Extinction
On Day 1, conduct acquisition of conditioned freezing and suppression of bar pressing, followed by extinction training
Note: vmPFC lesions had no effect on acquisition or extinction on Day 1
View evidence from paper
“On Day 1 vmPFC lesions had no effect on acquisition or extinction of conditioned freezing and suppression of bar pressing”
Day 2 - Recovery Assessment
On Day 2, assess recovery of conditioned fear responses after a long delay following extinction training
Note: Sham rats recovered only 27% of acquired freezing, while vmPFC-lesioned rats recovered 86%
View evidence from paper
“On Day 2 sham rats recovered only 27% of their acquired freezing, whereas vmPFC-lesioned rats recovered 86%”