The amygdala is a structure in the brain whose functions include attaching emotion to memory, memory consolidation, processing emotion, and regulating aggression.  Shifts in its functioning are known to be associated with fear, stress, and trauma. In a study published this month in Biological Psychiatry:  Cognitive Neuroscience and Neuroimaging, researchers found that the veterans with a diagnosis of PTSD–post-traumatic stress disorder had parts of the amygdala that were smaller and parts that had grown larger.

The study did not address the meaning of these volume shifts in the various nuclei but does point to significant brain changes as a result of trauma exposure.  It is similar to a series of other studies which also point to structural and connectivity changes.

A summary of the most recent study may be found here.