Final answer:
The brain region not directly connected with PTSD is the Corpus callosum. The medial prefrontal cortex, amygdala, and hippocampus, all parts of the limbic system, are implicated in the emotional processing and memory functions that are affected in PTSD.
Step-by-step explanation:
Each of the following is a specific brain region directly connected with post-traumatic stress disorder (PTSD) EXCEPT the Corpus callosum. The regions that are associated with PTSD include the medial prefrontal cortex, which has roles in fear extinction and emotion regulation; the amygdala, involved in emotional processing and fear responses; and the hippocampus, which is implicated in emotional processing and memory. The corpus callosum, however, primarily facilitates communication between the two cerebral hemispheres and is not directly connected with PTSD pathology.
Research has demonstrated that the structure and function of the hippocampus are linked to mood and anxiety disorders, including PTSD. Individuals with PTSD often show reductions in hippocampal volume, which might stem from decreased neurogenesis and dendritic branching. While there is a correlation between hippocampal volume and PTSD, causal claims cannot be made due to the nature of correlational research. Improvements in behavioral symptoms and increases in hippocampal volume are seen following pharmacological or cognitive-behavioral therapy for PTSD.
The amygdala and hippocampus are part of the limbic system, which is fundamental in mediating emotional response and memory. Both structures have been subject to studies in the context of mood and anxiety disorders, showing variations in structure and function that correlate with these conditions.