Biofeedback is a method of helping patients become aware of involuntary physiological responses, which enables them to learn to consciously control them. Examples of responses are changes in heart-rate, blood pressure, brain wave frequencies (associated with states of alertness and relaxation), and the electrodermal response. Biofeedback can be useful in learning to deal with a wide range of problems, including stress, insomnia, chronic pain and epilepsy.