The human brain evolved in three parts: the lizard brain (brain stem), mammalian brain (limbic system), and human brain (cortex). The brain stem controls vital functions like breathing and regulates arousal states. The limbic system is associated with emotions, motivation and memory formation. It includes the thalamus, hypothalamus and amygdala. The cortex is the outer layer and most recently evolved part responsible for higher-level thinking, language, and executive functioning. It is divided into four lobes - frontal, parietal, temporal, and occipital - each associated with different cognitive and sensory functions.