Habituation is a decrease in responsiveness to a repeatedly presented stimulus. Habituation has an important role in attention. By reducing our sensitivity to a constant source of stimulation, it releases attention resources to process new distinct items. In this book, the authors discuss the theories, characteristics and biological mechanisms of habituation. Topics include the important roles for matrix metalloproteinases and cell adhesion molecules in long-term potentiation (LTP), habituation, and drug addiction; habituation theories in current models of chronic tinnitus; habituation deficits in childhood disorders and traumatic brain injury; a mathematical description of habituation and recovery of the head-shake response in rats; and the influence that habituation has on the sensory system and its involvement in many ENT fields.