Implicit and explicit emotional memory recall in anxiety and depression: Role of basolateral amygdala and cortisol-norepinephrine interaction

Anxiety and depression are linked to both explicit and implicit memory biases, which are defined as the tendency to preferentially recall emotionally negative information at conscious and subconscious levels, respectively. Functional connectivity (FC) of the basolateral amygdala (BLA) and related stress hormones (i.e., cortisol and norepinephrine) are purportedly implicated in these biases. However, previous findings on memory biases in anxiety and depression have been inconsistent, likely due to their symptomatic complications. Therefore, the underlying neurobiological mechanism remains unclear. We thus investigated whether anxiety and depression as premorbid predispositions are related to the memory biases, and whether FC of BLA, cortisol, and 3-methoxy-4-hydroxyphenylglycol (MHPG: a major metabolite of norepinephrine) would affect the anxiety/depression-related biased memory recall in 100 participants without psychiatric symptomatology. Psycho-behavioral assessment, resting-state fMRI scans, and saliva collection at 10-points-in-time across two days were conducted. Correlations of memory biases with anxiety/depression and neurobiological markers were explored. As a result, neither anxiety nor depression were correlated with explicit memory bias to negative (vs. positive) information, although depression was associated with better recall of the negative stimuli only when they were perceived as self-relevant. In contrast, both anxiety and depression were correlated with implicit memory bias; however, the effects were solely explained by anxiety. Furthermore, FC of the BLA with subgenual anterior cingulate cortex (sgACC) and the synergetic effect of cortisol and MHPG uniquely affected the implicit memory bias. These findings suggest that anxiety facilitates an initial snapshot of negative information and can be accompanied by depression when the information creates negative semantic associations with the self. The BLA-sgACC neural connectivity and cortisol-norepinephrine interaction that are associated with the implicit memory bias might be one of the important neurobiological targets in the prevention and treatment for comorbid anxiety and depressive disorders.