A complex system of nerve pathways and networks in the brain, involved in expression of instinct and mood in activities of the endocrine and motor systems of the body. Regions of the brain involved include; the amygdala, hippocampus, hypothalamus, striatum. Activites controlled include self-preservation (e.g. fighting, finding food) and preservation of the species (e.g. reproduction), the expression of rage, fear and pleasure, and establishment of memory patterns.