The amygdala is well renowned for its role in memory, particularly during fear conditioning. During Pavlovian fear conditioning, the lateral amygdala receives input from both the conditioned stimulus (CS) and the unconditioned stimulus (US) and is thought to be the site of plasticity for the association between the CS and the US (Phelps, 2009). The amygdala also becomes active in humans during exposure to strong aversive odorants, suggesting that the amygdala makes use of the transduction of negative odorants in some way as to lead to the consolidation of fear memories, catalyzing the retention of experience surrounding the exposure (Zald; Pardo, 1997). The amygdala also responds to identify reward representations, working with the orbitofrontal cortex to help promote behavior that can result in rewards (Gottfried et al., 2003). The amygdala, therefore, seems pivotal in labeling the retention of past experiences with an emotional tag, supplying the organism with an emotional context in which to interpret the memory, and with any luck, an adaptive advantage.
However, the amygdala also seems to have a role in the formation of long term memory; meaning that not only do the various amygdalar nuclei tag memories, they also seem to be part of a process that reinforces lasting memory retention. Recent fMRI analysis has found that localized metabolic increases in the amygdala during moments of insight can be used as a predictive measure for which solutions derived from insight will be remembered one week after the exercise (Rubin et al. 2011). In this study the insight task utilized camouflaged images, which were subsequently revealed (allowing for a moment of insight), but the experiment coordinators went to great lengths to ensure that the images themselves were neutral, i.e. nothing grotesque or arousing. This is surprising, because the amygdala was not obviously tagging the learning experience (the insight) with emotion, in fact many of the participants only reported mild feelings of bemusement or indifference during the task. Depending upon interpretation, the amygdala may have performed one or both of the following roles; the very use of the amygdala meant that the insight moment was a subconscious emotional event, or/and the amygdala was performing a non-emotion based task. Regardless of the interpretation, the amygdala clearly has a role in long term memory retention. An interesting follow-up to the Rubin study would be to investigate whether or not the amygdala became active during the testing of long term memory retention, i.e. is there increased amygdala activation during exposure to the camouflaged images that one week ago elicited an increased response during insight.