Abstract
Neurobiological research with animals strongly suggests that the brain systems which mediate emotion overlap with those that mediate cognition to such a degree that it is difficult, if not impossible, to maintain any clear distinction between them. Possible reasons for this overlap are discussed; and a model of brain systems that simultaneously subserve emotion and cognition is presented. The model postulates the existence of three fundamental systems of this kind in the mammalian brain: a behavioural approach system, a fight/flight system, and a behavioural inhibition system. The neuropsychology of each of these systems is briefly presented.