The limbic system is a system of nerve pathways and networks in the brain, involving several different nuclei, that is involved in the expression of instinct and mood in activities of the endocrine and motor systems of the body. Among the brain regions involved are the the amygdala, hippocampal formation, and hypothalamus.

The activities of the body that are governed are those concerned with self-preservation (e.g., searching for food and fighting) and preservation of the species (e.g., reproduction and the care of offspring), the expression of fear, rage, and pleasure, and the establishment of memory patterns.