the view, now outmoded, in which the brain contains three layers showing its evolutionary growth. The first and eldest is the archipallium, also called R- complex; the second is the paleo- mammalian system, also called the limbic system; and the most recently developed is the neopallium, also known as the neocortex.
TRIUNE BRAIN: “The concept of the triune brain was posited by Paul D. MacLean, an American doctor and neurophysiologist.”