Birds have the ability to engage in unihemispheric sleep, or sleep with half of their brain. But, they can only do so during NREM sleep. When the left half of the brain is asleep and the right half of the brain is awake, for example, the right eye is closed and the left eye is open.

Humans sort of have unihemispheric sleep. On the first night of sleeping in an unfamiliar place, one half of the brain goes into a much deeper sleep than the other half. But, both eyes are closed. Not as cool, but what are you going to do, ya know?

Rattenborg, Niels C.; Lima, Steven L.; Amlaner, Charles J. (1999). “Half-awake to the risk of predation”. Nature. 397 (6718): 397–398.

Tamaki, Masako, et al. “Night watch in one brain hemisphere during sleep associated with the first-night effect in humans.” Current biology 26.9 (2016): 1190-1194.

After a night of poor sleep, you’d think that you should catch up on sleep by sleeping in the next day. But, by sleeping in, you won’t feel tired the following night, and you’ll stay up late again and wake up late again.

In order to develop a better sleep schedule, it is best to go to bed at the same time and wake up at the same time regardless of the day of the week and how bad a night of sleep was.

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

According to a 1992 study, bad dreams are more likely to occur following a stressful event.

This studied examined the percentage of subjects who experienced a bad dream after the 1989 Bay Area earthquake. Those who lived closest to the epicenter and experienced the most stress had the most nightmares. Those who lived furthest from the epicenter and did not feel as stressed experienced the fewest nightmares.

Thus, the intensity of stress is positively associated with the number of nightmares.

Wood, J. M., Bootzin, R. R., Rosenhan, D., Nolen-Hoeksema, S., & Jourden, F. (1992). Effects of the 1989 san francisco earthquake on frequency and content of nightmares. Journal of Abnormal Psychology, 101(2), 219-224. doi:http://dx.doi.org/10.1037/0021-843X.101.2.219

Your hunger is controlled by 2 hormones: leptin and ghrelin. Leptin decreases your appetite and communicates to the brain the you’re full. Conversely, ghrelin increases your appetite and communicates to the brain that you’re hungry.

When you’re sleep deprived, leptin levels drop and ghrelin levels rise, making you feel hungrier than usual.

While we will admit it is clever joke, the condition is not called “insom-nom-nom-nom-nom-nia.”

Spiegel, Karine, et al. “Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite.” Annals of internal medicine 141.11 (2004): 846-850.

Remember Process-S and Process-C from Day 1? Well, we’re about to go into a bit more detail.

Think of Process-C, the circadian rhythm, as a sine curve that naturally rises and falls throughout the 24-hour period. Think of Process-S as a curve that continues to rise relentlessly as you remain awake but falls as you sleep. The greater the distance between the 2 curves, the more tired you feel.

So, when you’re pulling an all-nighter and not sleeping like you’re supposed to, Process-C (your drive to be awake) is at its lowest point and Process-S (your drive to be asleep) continues to rise. At this point, you feel completely exhausted.

But, as the morning comes along, the Process-C curve begins to rise as your circadian rhythm naturally increases your drive to be awake. Even though Process-S is still rising into the morning, thanks to Process-C, the distance between the two curves is not as great as it was at night, and you don’t feel as tired as you did.

But, just wait until your Process-C naturally falls again later in the day.

Borbély, A. A. (1982). A two process model of sleep regulation. Human Neurobiology, 1(3), 195-204. Retrieved fromhttps://search.proquest.com/docview/616860359?accountid=14496

Although Sigmund Freud suggested that dreams play out our repressed wishes–a wish that our heart makes, if you will–his theory is scientifically invalid.

According to Freud, individuals have repressed wishes that, in their raw form, are too scary for our sleeping minds to handle. This “latent content” is censored through a filter. Our dreams then depict “manifest content” that we can recall. While Freud claimed he could reverse-engineer this process and reveal our our heart’s wishes and the truth behind our dreams, this scientific theory cannot be proven correct or incorrect because it is not testable. Additionally, different psychoanalysts provide different interpretations of the same dream, pointing to the subjectivity of Freud’s “science.”

Fosshage, J. L., & Loew, C. A. (1987). Dream interpretation: a comparative study. New York: PMA Publishing corp.

All puns aside, sleepwalking is a type of parasomnia. Like other parasomnias, sleepwalking typically occurs as your body is trying to wake up from deep slow-wave sleep (Stages 3 and 4 of NREM sleep). The autonomic nervous system, which controls automatic bodily functions like your breathing, is suddenly jolted. Your brain is forced to wake up from its deep sleep but gets stuck in the middle of that and wakefulness. As a result, your brain is in deep sleep, but your body is acting out behaviors as if you were awake.

You may be wondering what’s going on in your brain when you’re sleepwalking. The cerebellum and motor cortex are highly active while the prefrontal cortex (responsible for logical reasoning) shows extremely low activity levels–lower than the levels seen during REM sleep.

Bassetti, C., Vella, S., Donati, F., Wielepp, P., & Weder, B. (2000). SPECT during sleepwalking. The Lancet, 356(9228), 484-485. doi:10.1016/s0140-6736(00)02561-7

Narcolepsy occurs when you have an overwhelming appetite for sleep during the day time. It can be described as an inability to resist sleep. The 4 key symptoms are excessive daytime sleepiness (unable to stay awake), sleep paralysis (inability to talk or move), hypnagogic hallucinations (vivid, scary dreams that result from falling immediately into a  severe form of REM sleep), and cataplexy (a sudden loss of muscle tones causing you to partially or totally collapse).

It is not narcolepsy if you fall asleep during a boring lecture and you’re sleep deprived.

National Institutes of Health. (n.d.). What Are the Signs and Symptoms of Narcolepsy? Retrieved April 13, 2017, from https://www.nhlbi.nih.gov/health/health-topics/topics/nar/signs

Jetlag occurs when we fast-forward or drag back in time our circadian rhythm. It’s a disruption of our circadian rhythm as a result of our crossing time zones. For that reason,  we struggle to function in the new time zone because there is a mismatch between our internal circadian clock and external time (new time zone) . So, you can be sleepy in the day in the new location because you are biologically supposed to be sleeping. Or, you can’t sleep at night because it’s daytime in your biological circadian rhythm time zone.

Arendt, J., & Marks, V. (1982). Physiological changes underlying jet lag. British Medical Journal (Clinical Research Ed.), 284(6310), 144–146.

While one occasion of waking up at 3 AM and not being able to fall back asleep does not constitute insomnia, there is a type of insomnia that describes that type of poor sleep.

Sleep maintenance insomnia is a type of insomnia that describes difficulty staying asleep throughout the night or difficulty going back to sleep after waking up during the night or early morning hours.

Ellis, G. (2014, Jul 08). Recent studies link sleep issues, diabetes. Philadelphia Tribune Retrieved from https://search.proquest.com/docview/1549956226?accountid=14496