Given its prominence in emotional regulation, we will attempt to summarise the status of current thinking regarding the amygdala by picking out some of the highlights from a recent review article by Hermans et al (2014). It opens as follows:

Dramatic behavioural changes resulted from such surgical procedures, including visual agnosia, hypersexuality, and profound alterations in emotional behaviours, including tameness and loss of fear. Current thinking, based on voluminous research on rodents, has converged on the so-called ‘modulation hypothesis’ of amygdala function. During an emotionally arousing episode, stress hormones (epinephrine, glucocorticoids) are secreted from the adrenal glands (as well as other ‘neurochemicals’ such as neurotransmitters, in the brain); these are engaged by the amygdala ‘to enhance the consolidation and storage of memory within other parts of the brain’ (Hermans et al, 2014: 3).

The focus of much of this work is a particular region of the amygdala, the basolateral complex (BLA). Across a very broad range of training tasks, typically high arousal tasks such as fear conditioning (though low arousing tasks too, such as maze navigation), an impressive volume of evidence has accumulated which ‘suggests that emotionally arousing learning experiences induce the release of norepinephrine in the amygdala’ (p 4). As different training paradigms clearly imply different brain systems, it is implied that the amygdala, the BLA in particular, exerts ‘influences on information processing in these different brains regions’ (p 4).

Close interaction with the hippocampus in particular has been implicated: one study showed that post-training administration of glucocorticoids in the hippocampus enhanced rats’ retention of inhibitory avoidance training, but that this was suppressed when noradrenergic activity in the BLA was blocked pharmacologically. Taking these findings together, the authors of the review conclude: