Persistence of fear memory across time requires the basolateral amygdala complex

Mammals evolved a potent fear-motivated defensive system capable of single-trial fear learning that shows no forgetting over the lifespan of the animal. The basolateral amygdala complex (BLA) is considered an essential component of this conditional fear learning system. However, recent studies chall...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 106; no. 28; pp. 11737 - 11741
Main Authors Poulos, Andrew M, Li, Veronica, Sterlace, Sarah S, Tokushige, Fonda, Ponnusamy, Ravikumar, Fanselow, Michael S
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 14.07.2009
National Acad Sciences
Subjects
Amygdala
Amygdala - physiology
Animal memory
Animals
Behavioral neuroscience
Biological Sciences
Brain
Conditioning, Psychological - physiology
Electric Stimulation
Fear
Fear & phobias
Fear - psychology
Forgetting
Freezing
Immunohistochemistry
Lesions
Male
Mammals
Memory
Memory - physiology
Memory recall
Mnemonics
Neuronal Plasticity - physiology
Rats
Rats, Long-Evans
Sensitization
Studies
Time Factors
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Summary:Mammals evolved a potent fear-motivated defensive system capable of single-trial fear learning that shows no forgetting over the lifespan of the animal. The basolateral amygdala complex (BLA) is considered an essential component of this conditional fear learning system. However, recent studies challenge this view and suggest that plasticity within other brain regions (i.e., central nucleus of the amygdala) may be crucial for fear conditioning. In the present study, we examine the mnemonic limits of contextual fear conditioning in the absence of the BLA using overtraining and by measuring remote fear memories. After excitotoxic lesions of the BLA were created, animals underwent overtraining and were tested at recent and remote memory intervals. Here we show that animals with BLA lesions can learn normal levels of fear. However, this fear memory loses its adaptive features: it is acquired slowly and shows substantial forgetting when remote memory is tested. Collectively, these findings suggest that fear-related plasticity acquired by brain regions outside of the BLA, unlike those acquired in the intact animals, do so for a relatively time-limited period.
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Communicated by Richard F. Thompson, University of Southern California, Los Angeles, CA, May 19, 2009
Author contributions: A.M.P. and M.S.F. designed research; A.M.P., V.L., S.S.S., and F.T. performed research; A.M.P. and R.P. analyzed data; and A.M.P., R.P., and M.S.F. wrote the paper.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0905257106