At the present time there is no definitive agreement among members of the medical community. OCD appears to be mediated by increased activity in the orbital frontal cortex and caudate nucleus of the brain. The orbital frontal cortex, located behind the eyebrows, is involved in the perception of fear and danger. The caudate nucleus is involved in one's ability to start and stop different thoughts and activities. OCD may also involve abnormal functioning of the neurotransmitter seratonin in the brain.