Patients often present with hyperphagia and rapid weight gain. Hypersexuality, hyperphagia, and aggressive outbursts are indicative of disinhibited instinctual drives. Decreased desire to eat is termed anorexia, while polyphagia (or "hyperphagia") is increased eating. CART hypoactivity in the hypothalamus of depressed animals is associated with hyperphagia and weight gain. The behavioral disturbances can be composed of hyperphagia, irritability, or sexual disinhibition. Lesions subsequently made in the hypothalamus of two paired rats resulted in hyperphagia and obesity. During the autumn hyperphagia, feeding becomes virtually the full-time task of American black bears. Knocking out vagal nerve receptors has been shown to cause hyperphagia (greatly increased food intake). In each pair, one rat became obese and exhibited hyperphagia. Knocking out vagal nerve receptors has been shown to cause hyperphagia. These biological factors can interact with environmental elements to further trigger hyperphagia. These eight mutations all cause extreme obesity in infancy, with hyperphagia.