Dwight is partially correct.

If a dream is defined more broadly as any sort of mental activity reported immediately upon waking up from sleep, then dreams can occur at every stage of the sleep cycle, not just REM sleep. This includes during the transition from wakefulness to sleep (hypnagogic dreams) and during the transition from sleep to wakefulness (hypnopompic dreams).

However, what most people constitute as “dreaming” does occur during REM sleep.

Foulkes, W. D. (1962). Dream reports from different stages of sleep. The Journal of Abnormal and Social Psychology, 65(1), 14-25. doi:10.1037/h0040431

During REM (dream) sleep, some areas of our brain are activated and some are de-activated. The following are the activated parts:

• Motor cortex – deals with voluntary motor control
• Cingulate cortex and amygdala – deals with emotions
• Occipital cortex – deals with visual processing
• Hippocampus – deals with memories

Based on this knowledge, we know that dreams draw on our memories and can be filled with movement, emotions,  visual components.

On the other hand, the lateral prefrontal cortex, which deals with rational, high-level decision making, is deactivated. Based on this piece of information, we can understand why dreams are so illogical and irrational.

McCarley, R. W., & Hoffman, E. (1981). REM sleep dreams and the activation-synthesis hypothesis. The American Journal of Psychiatry, 138(7), 904-912. doi:http://dx.doi.org/10.1176/ajp.138.7.904

The mechanisms of REM sleep not only allow you to dream but also allow you to do so safely. There is a signal that is sent down your brain stem and through your spinal cord to inhibit all nerves connected  to your skeletal muscles. Experiencing REM sleep paralysis,  you cannot move. This evolution turns out to be good for us! If you ever act out in your dream (such as jumping out the window), you body cannot physically do those things because of REM sleep paralysis.  In this way, the mind paralyzes the body so that the mind can dream safely!

Hishikawa, Y., & Shimizu, T. (1994). Physiology of REM sleep, cataplexy, and sleep paralysis. Advances in Neurology, 67, 245-271.

No need to buy the light-blocking curtains. Jean Jacques d’ Ortous de Mairan’s 1729 experiment already demonstrated that the 24-hour circadian rhythm is not dictated by the dark/light cycle and sunlight. It is caused within the biology of organisms. If we take ourselves out of the outer world, we will still continue that rhythmic behavior. And, the French geophysicist showed this by  conducting an experiment on the leaf movements of a heliotrope plant over 24-hour periods. As the day time arrives, the plant unfolds its leave; yet, when darkness comes, the leaves collapses. Initially, everyone thought this behavior was governed by external forces (i.e. sunlight). However, Jean discovered that the leaves still exhibit this same behavior when he placed the flower away from the sun in a dark room. His experiment proved that circadian rhythm still persists in absence of external cues like light.  

(de Mairan, 1729)

Our circadian rhythm is the rhythm that is generated and controlled from within us. It is the biological clock that resides in our brains. It is endogenous. Circadian rhythms help us regulate our sleep and wake cycle. In addition, it regulates our eating and drinking habits, body temperature, and hormone release. The human circadian rhythm is approximately 24 hours AND 10 minutes. All living species (including bacteria surviving more than 24 hours) function on a  circadian rhythm.

Kleitman, N. (1963). Sleep and wakefulness. Chicago: University Press.

Numerous research studies have shown that naps can have positive benefits for our declarative, fact-based memory. One study showed that infants were better able to hold onto memories if they napped after learning. Another study showed that this memory enhancement was positively correlated with the number of sleep spindles produced during naps. Similarly, in middle school students, naps after class helped students to recall information days later.

Timely sleep facilitates declarative memory consolidation in infants. (2015). Proceedings of the National Academy of Sciences of the United States of America., 112(5), 1625-1629. Retrieved from https://search.proquest.com/docview/1803136049?accountid=14496

Kurdziel, L., Duclos, K., & Spencer, R. M. C. (2013). Sleep spindles in midday naps enhance learning in preschool children. PNAS Proceedings of the National Academy of Sciences of the United States of America, 110(43), 1-6. doi:http://dx.doi.org/10.1073/pnas.1306418110

Lemos, N., Weissheimer, J., & Ribeiro, S. (2014). Naps in school can enhance the duration of declarative memories learned by adolescents. Frontiers in Systems Neuroscience, 8, 6. doi:http://dx.doi.org/10.3389/fnsys.2014.00103

If you can’t fall asleep after 20 or 30 minutes or can’t fall back asleep after waking up in the middle of the night, it’s a good idea to get out of bed and do something calm and quiet (and that doesn’t involve technology). The longer you stay in bed awake, the more time your brain has to begin associating your bed with wakefulness.

Go back to bed when you start to feel sleepy again.

Edinger, J. D., Wohlgemuth, W. K., Radtke, R. A., Marsh, G. R., & Quillian, R. E. (2001). Cognitive Behavioral Therapy for Treatment of Chronic Primary Insomnia. Jama, 285(14), 1856-1864. doi:10.1001/jama.285.14.1856

The science is still out. The scientific sleep world still doesn’t fully understand the side effects of sleeping too much (i.e. hypersomnia). If there’s such a thing as too much wakefulness and not enough sleep, then perhaps there is such a thing as too much sleep and not enough wakefulness.

But, there is a name for that terrible, groggy feeling you experience after sleeping for 11 hours versus your normal 8 hours. That’s called the sleep hangover effect.

Vaze, K. M., & Sharma, V. K. (2013). On the adaptive significance of circadian clocks for their owners. Chronobiology International, 30(4), 413-433. doi:http://dx.doi.org/10.3109/07420528.2012.754457

This guy might be onto something.

Sleep improves the consolidation of procedural motor skill memory–whether that memory involves riding a bike or performing athletic activities. More specifically, research reveals that stage 2 NREM sleep toward the end of the night plays an essential role in improving motor procedural memories.

This guy might be napping to improve his motor skill performance. You never know.

Practice with sleep makes perfect (sleep dependent motor skill learning) .Walker, M.P., Brakefield, T., Morgan, A., Hobson, J.A., and Stickgold, R.Neuron. 2002; 35: 205–211

Maybe that statement is a bit of an exaggeration. But, it is true that your level of sleep deprivation could lead to a state of impairment that is equivalent to that of a legally drunk individual. In fact, on average, it takes about 20 consecutive hours of wakefulness for you to reach the point of being legally drunk. In other words, an individual with 20 hours of sleep deprivation experiences the same performance in terms of psychomotor vigilance tasks (PVTs or lapses or micro-sleeps) compared to his baseline performance as an individual who is legally drunk.

Dawson, D., & Reid, K. (1997). Fatigue, alcohol and performance impairment. Nature, 388(6639), 1-235. doi:http://dx.doi.org/10.1038/40775