Intellectual disabilities have been related to the dysfunction of the prefrontal cortex. The prefrontal cortex is located on the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas. This brain region has been implicated in planning complex cognitive behaviours, personality expression, and moderating correct social behaviour. This book presents a review of present day evidence of the reduction of the prefrontal cortex; links between abnormalities and functional or clinical features of intellectual disabilities such as schizophrenia. The book presents the latest research from around the world in this field.