Final answer:
REM sleep behavior disorder (RBD) is an abnormality of REM sleep characterized by the absence of normal muscle paralysis, allowing the person to be physically active during REM sleep, which can lead to disruptive and potentially harmful behaviors.
Step-by-step explanation:
The symptom known as REM sleep behavior disorder (RBD) is an abnormality of REM sleep. RBD occurs when muscle paralysis that normally accompanies the REM phase of sleep is absent. This leads to the unusual phenomenon where individuals are physically active during their REM sleep, potentially engaging in behaviors like kicking or yelling, a consequence of action-filled or disturbing dreams. These activities can result in injury to the person or bed partner and significantly disrupt sleep. RBD is notable because people with this disorder do not remember these activities upon waking.
REM sleep typically involves paralysis of voluntary muscles, preventing movement, which is why RBD is considered a parasomnia—an undesirable motor or experiential event occurring in sleep. RBD has been connected to various neurodegenerative diseases and is commonly treated with medications such as clonazepam and sometimes melatonin. Moreover, adjustments may be made in the sleeping environment to enhance safety.