Which of the following statements about sleep-wake cycles is false?

• A. The sleep-wake cycle is regulated by both internal biological clocks and external cues such as light.
• B. Circadian rhythms typically follow a roughly 24-hour cycle in humans.
• C. REM sleep occurs only once during the entire sleep period.
• D. Disruptions to the sleep-wake cycle can negatively affect mood and cognitive performance.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of the sleep-wake cycle, which is primarily regulated by circadian rhythms—internal biological clocks that follow an approximately 24-hour cycle and are influenced by external cues like light.
2. Step 2: Review the role of REM (Rapid Eye Movement) sleep within the sleep cycle. Recognize that REM sleep does not occur just once but multiple times during a typical sleep period, cycling through several stages.
3. Step 3: Analyze each statement given in the problem to determine its accuracy based on your knowledge of sleep science and circadian rhythms.
4. Step 4: Identify that the statement claiming 'REM sleep occurs only once during the entire sleep period' is false because REM sleep recurs multiple times in cycles throughout the night.
5. Step 5: Confirm that the other statements about the regulation of the sleep-wake cycle by internal and external factors, the typical 24-hour circadian rhythm, and the negative effects of disruptions on mood and cognition are true.