The mental body is, in the seven-layer aura model, the third layer, lying beyond the emotional body and associated with thought, ideas and the intellect, said to be structured and often described as yellow or bright where mental activity is strong. In the scheme popularised by Barbara Brennan's Hands of Light and derived from Theosophical subtle-body doctrine, the layers ascend from the dense etheric nearest the body through the emotional and mental to the more rarefied spiritual layers beyond, the mental body marking the level of the reasoning and conceptual mind. It corresponds broadly to the mental sheath, the manomaya kosha, of the Indian tradition from which the Theosophists drew.
The seven-layer model is a construction of modern esotericism, assembled in the late nineteenth and twentieth centuries; it is presented here as a description of a belief tradition, not as an anatomical or scientific account, since there is no evidence for the existence of an aura, and no medical or diagnostic claim is intended.
Sources Hands of Light: A Guide to Healing Through the Human Energy FieldBarbara Ann Brennan with Rainbow Body: A History of the Western Chakra System from Blavatsky to BrennanKurt Leland