The amygdala, part of the limbic system, is responsible for the information processing of fearful stimuli and mentally associating behavior with punishment. Because individuals with ODD have deficits in conditioning, it is thought that impaired functioning of the amygdala is correlated with deficits in processing of fearful stimuli. Studies have found reductions in gray matter in a variety of brain regions when comparing ODD patients to control groups. Additionally, fMRI studies reveal similar results which confirm an association exists between amygdala functioning and disruptive behavior disorders.