A study on polysomnographic observations and subjective experiences under sensory deprivation.

We investigated the relationship between subjective experiences and polysomnographic observations under sensory deprivation (SD). The results can be divided into two types: (i) visual images were perceived frequently, accompanied by alpha waves or theta waves in electroencephalogram and frequent rapid eye movements (REM); (ii) the subjects fell in deep sleep without perception of visual images. The perceptions of visual images with alpha waves or theta waves and REM are supposed to be different from those in usual wakefulness and sleep. These results suggest that the SD could disclose different aspects of consciousness from the conventionally categorized states such as wakefulness and sleep.