Inactivation of the infralimbic but not the prelimbic cortex impairs consolidation and retrieval of fear extinction.
Rats were subjected to one or two cycles of context fear conditioning and extinction to study the roles of the prelimbic cortex (PL) and infralimbic cortex (IL) in learning and relearning to inhibit fear responses. Inactivation of the PL depressed fear responses across the first or second extinction but did not impair learning or relearning fear inhibition (experiment 1). Inactivation of the IL did not affect inhibition across the first extinction but disrupted its long-term retention. Inactivation of the IL impaired inhibition across the second extinction, and inactivation before or after this extinction impaired long-term retention (experiments 2 and 3). Inactivation of the IL before the retention test restored extinguished fear responses (experiment 4). These results show for the first time that neuronal activity in the PL is involved in the expression of fear responses but not in the learning that underlies long-term fear inhibition. They also confirm that the IL is involved in this inhibitory learning: Specifically, they show that the IL is critical for consolidation and retrieval of this inhibitory learning. The role of the IL is discussed in terms of a contemporary neural model of fear extinction.
Laurent
Vincent
V
School of Psychology, The University of New South Wales, New South Wales, Australia.
Westbrook
R Frederick
RF
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D004597:Electroshock / Q000009:adverse effects; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects / Q000502:physiology; D018755:GABA Agonists / Q000009:adverse effects / Q000494:pharmacology; D007266:Inhibition, Psychological; D007859:Learning Disabilities / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D008032:Limbic System / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology*; D009118:Muscimol / Q000009:adverse effects / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D018755:GABA Agonists; D009118:Muscimol