Sensory deprivation refers to the process of restricting or eliminating sensory input to the brain. The concept is often used in therapy or meditation. Synonyms for sensory deprivation include sensory isolation, perceptual deprivation, and floating. Sensory isolation occurs when someone is removed from any external stimulus, thereby reducing sensory input. Perceptual deprivation occurs when someone is intentionally deprived of stimuli in a particular sensory modality, such as sight or hearing. Floating involves the use of a float tank, where an individual floats in saltwater while wearing earplugs and often with the lights dimmed, to achieve a state of sensory deprivation and relaxation.