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Lead section

Scientists have discovered that there is a set of brain connections that determine how fear memories are stored and recalled. While studying rats' ability to recall fear memories, researchers found a newly identified brain circuit is involved. Initially, the pre-limbic prefrontal cortex (PL) and the basolateral amygdala (BLA) were identified in memory recall. A week later, the central amygdala (CeA) and the paraventricular nucleus of the thalamus (PVT) were identified in memory recall, which are responsible for maintaining fear memories. This study shows how there are shifting circuits between short term recall and long term recall of fear memories. There is no change in behavior or response, only change in where the memory was recalled from.

Reference: Ashley Yeager. (2015, January 19). Newly identified brain circuit hints at how fear memories are made. Science News. Retrieved February 17, 2019, from AccessScience: https://www-accessscience-com.ezproxy3.lhl.uab.edu/content/newly-identified-brain-circuit-hints-at-how-fear-memories-are-made/SN0122151

Amygdala

The amygdala is not exclusively the fear center, but also an area for responding to various environmental stimuli. Several studies have shown that when faced with unpredictable neutral stimuli, amygdala activity increases. Therefore, even in situations of uncertainty and not necessarily fear, the amygdala plays a role in alerting other brain regions that encourage safety and survival responses.

Grupe, D. W., & Nitschke, J. B. (2011). Anxiety disorders and the amygdala. In AccessScience. McGraw-Hill Education. https://doi-org.ezproxy3.lhl.uab.edu/10.1036/1097-8542.YB110087

Amygdala is involved in acquisition, storage, and expression of conditioned fear memory.

Kim, J. J., & Jung, M. W. (2006). Neural circuits and mechanisms involved in pavlovian fear conditioning: A critical review. Neuroscience and Biobehavioral Reviews, 30(2), 188-202. doi: http://dx.doi.org.ezproxy3.lhl.uab.edu/10.1016/j.neubiorev.2005.06.005

Molecular Mechanisms

Intra-Amygdala Circuit

Neurons in the basolateral amygdala are responsible for the formation of conditioned fear memory. These neurons project to neurons in the central amygdala for the expression of a conditioned fear response. Damage to these areas in the amygdala would result in disruption of the expression of conditioned fear responses.

Lesions in the basolateral amygdala have shown severe deficits in the expression of conditioned fear responses. Lesions in the central amygdala have shown mild deficits in the expression of conditioned fear responses.

Kim, J. J., & Jung, M. W. (2006). Neural circuits and mechanisms involved in pavlovian fear conditioning: A critical review. Neuroscience and Biobehavioral Reviews, 30(2), 188-202. doi: http://dx.doi.org.ezproxy3.lhl.uab.edu/10.1016/j.neubiorev.2005.06.005