Persistence of fear memory across time requires the basolateral amygdala complex.

Proc Natl Acad Sci U S A 2009 Jul 30;106(28):11737-41. Epub 2009 Jun 30.

Department of Psychology and Brain Research Institute, University of California, Los Angeles, CA 90095, USA.

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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http://dx.doi.org/10.1073/pnas.0905257106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710655PMC
July 2009
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