Why people have dreams is still a mystery to neuroscientists. Humans spent about ⅓ of their lives dreaming, but humans forget half of their dreams 5 minutes after waking up or even right after. Dreams  reflect a process of long term memory consolidation, and understanding of previous knowledge and/or chain of events. Dreams can be related to emotional and physical state, which may have a connection to sleep paralysis. There are many types of dreams such as lucid dreams which are related to the state of consciousness. The changing nature of dreams is explained by the concentration of the stress hormone cortisol which increases over the stages of sleep.

Brain activity changes throughout the night in cycles of 90 to 110 minutes when people are asleep (Chara). There are 4 stages of sleep, the first two are called D-sleep which is connected to memory consolidation and the processing of thoughts. The other two stages are called S-sleep which is essential for rest from the physical work of the day, the body recuperates in this time. Stage 1 is accompanied by rapid eye movements or REM. When people are awakened from REM, they report dreams 80 percent of the time, however, in NREM (no rapid eye movements) people report dreams 20 percent of the time. REM dreams tend to have more vivid, emotional or sensational plots, these dreams are most likely to be recalled. During the night, the greater wakefulness and the higher frequency of dreaming is linked with more frequent dream recall (Chara). Dream content varies on the stage of sleep and the time of night. Content and plot depends on personality, as well as physical and emotional conditions. Environmental factors are also considered important in shaping the nature of the dream. The probability of an event occurring in a dream depends on how emotional the event was (Chara). In other words, the more emotional an event the greater chance of it occurring in a dream. Events taking place during a person's sleep can also affect the plot of the dream. Temperature changes, light flashes and sounds can be detected by a person’s senses, which can then end up being a part of the plot. Nightmares can be put into three categories, most unpleasant dreams take place in the REM stage of sleep. These dreams are caused by everyday stress and problems. Night terrors have known to take place in stage 4 and are specifically known for sudden waking and terror-stricken reactions. Stress disorders can occur in any stage of sleep such as PTSD which is caused by life threatening events. Some people have also been known to have sleep paralysis which leads to hallucinations (Chara).

Dreams reflect a process of long term memory consolidation and emotional understanding. Long-term memory consolidation involves interaction among several brain systems. REM sleep is especially important for emotional information, and procedural memory. Memories are best consolidated in the REM stage of sleep (Payne, Jessica D., and Lynn Nade l). NREM sleep is highly important for episodic memories. Cortisol level varies over the night’s sleep. Cortisol levels have been known to rise throughout the night, explaining the nature of dreams.. It has been known to have both quick and delayed effects on neural functions. High levels of cortisol during REM sleep affects episodic memories and can also alter memory function. The hippocampal system and the neocortex work to recreate episodic memories 

(Payne, Jessica D., and Lynn Nade l). High levels of cortisol can cause memory deficits preventing any episodic memory consolidation. Stress hormone cortisol plays an important part in controlling the state of memory systems when someone is asleep.

Dreams are not real experiences so the brain does not mark them as important to remember causing people to forget their dreams. Remembering events that happen overnight are hard to remember since sleep makes people forget events that they may have experienced. People are more likely to remember the very last dream they had before waking up (Young Timothy). Lucid dreaming is when someone is conscious and is aware that they are dreaming. This is most common among children since their brains are still maturing. Scientists believe that studying what goes on in someone’s brain while they are lucid dreaming could unravel some of the inner working of the human brain, and help doctors understand mental health problems (Powell, Jessica).

Many credible inferences have been made about why people have dreams, but there is no rock solid scientific explanation explaining dreams and their meaning.  Dreams could have the power of revealing some of the complicated inner workings of the human brain, but can also uncover details about someone’s life  socially, mentally, biologically, and physically.

Works Cited

Chara, Paul J., Jr. "Dreams." Salem Press Encyclopedia Of Health (2014): Research Starters. Web. 26 Nov. 2016.

POWELL, JESSICA. "The Power Of LUCID DREAMING." Good Health (Australia Edition) (2015): 62-65. Consumer Health Complete - EBSCOhost. Web. 26 Nov. 2016.

Payne, Jessica D., and Lynn Nadel. “Sleep, Dreams, and Memory Consolidation: The Role of the Stress Hormone Cortisol.” Learning & Memory11.6 (2004): 671–678. PMC. Web. 26 Nov. 2016.

ncbi.nlm.nih.gov/pmc/articles/PMC534695/

 Young, Timothy.,”Why do we dream.”, Mayo Clinic, (2014). Web. 26 Nov. 2016

mayoclinichealthsystem.org/hometown-health/speaking-of-health/why-do-we-dream