The deficit syndrome is a domain of schizophrenic psychopathology defined by the presence ofprimarynegative symptoms that areenduringfeatures of a patient's function between periods of relapse. Lesions of the putative neural circuit underlying social affiliation and social behavioral cues in nonhuman primates and other mammals cause behavioral impairments in animals that model the diminished social drive, poverty of speech, and blunted affect of the deficit syndrome. Components of this circuit include the amygdala, periamygdalar cortex, and part of the prefrontal cortex. Abnormal function of this functional circuit may underlie the deficit syndrome.