Is the contribution of the amygdala to the sex- and enhancement-related effects of emotional memory time-dependent?

A new focus in the field of emotional memory is the study of sex-related differences. Whether the sex-related lateralization of amygdala function (i.e., the female-left/male-right effect) in the emotional enhancement of memory (EEM) is time-dependent remains unclear. To evaluate this phenomenon, we conducted a two time-point study (20 min vs. 24h) using fMRI and behavioral paradigms. We found that the right amygdala predicted 20-min EEM, while the left amygdala predicted 24-h EEM. The sex-related lateralization of amygdala function was not detected in either the 20-min or the 24-h EEM. Our results further confirm and extend the idea that the amygdala exhibits a lateralized and time-dependent dissociation, occurring even in the 24-h EEM relative to the 20-min EEM. The present and previous studies indicate that sex-related lateralization of amygdala function occurs in the 2- to 3-week EEM, but it does not occur in the 1-week, 24-h, or less than 30-min EEM, suggesting that this effect on emotional memory may also be time-dependent. Copyright 2009 Elsevier Inc. All rights reserved.