Treating anxiety, depression and other disorders may depend on the amygdala, a part of the brain that controls strong emotional reactions, especially fear. But a deep understanding of this structure has been lacking. Now scientists at the University of California, Davis have identified new clusters of cells with differing patterns of gene expression in the amygdala of humans and non-human primates.

The work could lead to more targeted treatments for disorders such as anxiety that affect tens of millions of people. The work is published in the American Journal of Psychiatry . "The amygdala is central to emotion processing in the brain, and is known to contribute to fear and anxiety ," said Drew Fox, associate professor in the UC Davis Department of Psychology and senior author on the paper.

For that reason, there has long been interest in whether variations in the size or structure of the amygdala are related to disorders such as anxiety and depression. However, it's increasingly clear that the overall size and structure of the amygdala is not a good predictor of emotional problems in life, Fox said. Recently, research in rodents has shown that each subregion of the amygdala contains many different cell types with distinct and sometimes opposing functions.

"This suggests that disorders emerge from alterations in specific cell types with distinct roles," Fox said. However, it is challenging to identify such cell types in humans or other primates, leaving the cellular landscape .