Melanin has many biological functions, including colouring the skin and hairs or feathers, strengthening plant cell walls and insect cuticle, absorbing light (and so providing photoreceptor shieldlng, thermoregulation, photoprotectlon), and it is an important free radical sink.
Medical Definition of autistic disorder. : autism Autistic disorder is classic autism, one of the more severe disorders on the spectrum. Persons with autistic disorder have substantial impairment in social skills, verbal communication, and cognitive and behavioral flexibility.âIsabelle Rapin , The New England Journal of Medicine, 1 Aug. 2002.
Autism spectrum disorder (ASD) is a range of complex neurodevelopment disorders, characterized by social impairments, communication difficulties, and restricted, repetitive, and stereotyped patterns of behavior.ater indicators include: 1  impaired ability to make friends with peers. 2  impaired ability to initiate or sustain a conversation with others. 3  absence or impairment of imaginative and social play. 4  stereotyped, repetitive, or unusual use of language.