Prosopagosia is an impairment in face identity recognition affecting both the memory for familiar faces and the ability to learn new faces. Prosopagnosia exists in a relatively pure form following focal brain injury to right or bilateral occipito-temporal cortex, but can also be a symptom of more diffuse or distributed damage. The type of prosopagnosia may differ depending on the lesion site, and the dominant impairment may be in perception or memory. Prosopagnosia also exists in a developmental form, where the ability to learn and recognize others' faces does not develop normally. The cause and underlying cerebral substrate of this developmental type is not known.