 One study suggested that areas of the prefrontal cortex are part of a network of regions including dorsal and pregenual cingulate, bilateral middle frontal gyrus, insula and superior temporal gyrus that appear to be hypoactive in people with MDD.However the authors cautioned that the exclusion criteria, lack of consistency and small samples limit results.The amygdala, a structure involved in emotional processing appears to be hyperactive in those with major depressive disorder.