From Wikipedia

Total Isolation

Sensory deprivation or perceptual isolation is the deliberate reduction or removal of stimuli from one or more of the senses. Simple devices such as blindfolds or hoods and earmuffs can cut off sight and hearing respectively, while more complex devices can also cut off the sense of smell, touch, taste, thermoception (heat-sense), and 'gravity'. Sensory deprivation has been used in various alternative medicines and in psychological experiments (e.g., see Isolation tank).

Short-term sessions of sensory deprivation are described as relaxing and conducive to meditation, if sometimes boring; however, extended or forced sensory deprivation can result in extreme anxiety, hallucinations, bizarre thoughts, depression and death.