Typically, in the rapid eye movement (REM) phase of sleep, atonia, inactivity in the muscles, is observed in the person. In the case of REM Sleep Behavior Disorder (RBD), sudden muscle movements and speech occur while the person is in REM sleep. These abnormal activities arise in relation to the person's dream at that moment. It is a particular type of parasomnia associated with some neurodegenerative diseases.
