The amygdalae are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing of memory and emotional reactions, the amygdalae are considered part of the limbic system.
Future studies have shown been proposed to address the role of the amygdala in positive emotions, and the ways in which the amygdala networks with other brain regions.
Recent studies have suggested possible correlations between brain structure, including differences in hemispheric ratios and connection patterns in the amygdala, and sexual orientation. Homosexual men tend to exhibit more female-like patterns in the amygdala than heterosexual males do, just as homosexual females tend to show more male-like patterns in the amygdala than heterosexual women do. It was observed that amygdala connections were more widespread from the left amygdala in homosexual males, as is also found in heterosexual females. Amygdala connections were more widespread from the right amygdala in homosexual females, as in heterosexual males. Current evidence suggests that formation of an individual’s sexual orientation occurs during fetal and neonatal development.
Amygdala volume correlates positively with both the size (the number of contacts a person has) and the complexity (the number of different groups to which a person belongs) of social networks. Individuals with larger amygdalae had larger and more complex social networks. They were also better able to make accurate social judgments about other persons’ faces. It is hypothesized that larger amygdalae allow for greater emotional intelligence, enabling greater societal integration and cooperation with others.
The amygdala processes reactions to violations concerning personal space. These reactions are absent in persons in whom the amygdala is damaged bilaterally. Furthermore, the amygdala is found to be activated in fMRI when people observe that others are physically close to them, such as when a person being scanned knows that an experimenter is standing immediately next to the scanner, versus standing at a distance.