Pervasive developmental disorders (PDDs) and autistic disorder (AD) are neurodevelopmental disorders with genetic basis and abnormal brain development, and characterized by severe and permanent deficits in many interpersonal relation areas like communication, social cognition and processing of emotional signs. Cognitive impairments in AD and other PDDs are tried to be explained by neuropsychiatric models like theory of mind deficits, executive dysfunction and weak central coherence. This article aimed to review neurobiological bases of social cognition and theory of mind which try to explain social cognition. PubMed medical search engine was queried to find out the studies and review articles on social cognition and theory of mind in AD and PDDs. Social cognition may be defined as the ability to interact in complex social areas with understanding the others' intentions and thoughts. The mind deficit is theorized to be one of the basic difficulties in autism. Individuals with autism have deficits in recognizing mental processes and mental representations of self and others'. Patients with AD have deficits in social functions which an important part of interpersonal interactions and functioning within a social group; like face recognition, eye contact and emotional expression recognition. Frontal lobe, temporal lobe, anterior cingulate cortex, fusiform gyrus, amygdala, posterior association cortex and their internal associations are brain areas associated with social cognition. Fusiform gyrus and amygdala are effective in face perception and recognition. Studies suggest that a deficit in amygdala may lead to social perceptional deficits like face identity and emotional expression recognition. It is determined that individuals with PDDs have hypoactivation in fusiform gyrus during perception of faces. Amygdala has a regulatory effect on fusiform gyrus and in lesions of amygdala, the hypoactivation of fusiform gyrus for emotional salient faces are parallel to the level of amygdala lesion. The common result of many studies is that the hypoactivation of fusiform gyrus is based on some processes related to amygdala. Superior temporal sulcus hypoactivations and abnormal volume measures were found in patients with autistic disorder. Superior tempral sulcus has a role in perception of social stimulus from gaze directions, and eye and body movements of others'. Autism can be defined as a social cognition disorder and is caused by deficits at microscopic and/or macroscopic levels in these brain systems. The review of the neurobiology of social cognition in AD and other PPDs defisits in amygdala and in connections of amygdala with other temporal areas including fusiform gyrus, superior temporal sulcus in early infancy and that leads to a deficit or absence of infant's interest for faces and other stimuli which are socially significant. This causes abnormal development of brain areas like fusiform gyrus which needs a stimulus dependent activation. When studying social cognition deficits, it is important to note that autism is not a disorder of a unique neuroanatomical system or cyclus; but it is a neurodevelopmental disorder in which many pervasive neural systems are affected
