The objective of this blog is to help the general population learn about various diseases related to Pulmonology. In such a way that people in general, if they suffer from a respiratory disease, can know it better or are able to promptly identify any symptoms that require medical evaluation and that this allows them to make broadly informed decisions with their doctor.
Today we will talk about dreaming, how it occurs, its development in childhood, its importance in human beings and we will briefly describe its main pathologies.
Dreams are an experience that occurs when we sleep that includes the presence of images, sensations, thoughts, emotions, speech and motor activity. Furthermore, it has also been suggested that this experience could be considered an emotional regulation of the human being. In fact, even before the stages of sleep were discovered, primarily REM, Freudian psychoanalysis considered dreams a way of accessing people's subconscious functions. Nightmares are, therefore, brain activity during sleep that is characterized by negative emotions and is constantly accompanied by bodily manifestations that are capable of waking the person up. 
Nowadays, it is known that a part of the brain called the hippocampus contributes to people's sleep, in part because it is associated with memory, so that part of what we dream could originate after an experience that was obtained while we were awake, although another part of the dream could come from non-conscious memory. 
To show how we dream, we will start by mentioning that brain activity is different when awake than when asleep. When we sleep there is a sleep architecture that is considered normal, where different phases of sleep will be observed; which in general terms we can first divide it into two phases: the REM phase and the Non-REM (NREM) phase. In turn, the latter is subdivided into: N1, N2 and N3 (also known as the slow wave sleep phase).  REM means “rapid eye movements” and as its name indicates, during this phase a series of cyclic eye movements occur accompanied by muscle paralysis in the rest of the body. This muscle paralysis has been considered a protective mechanism to avoid acting out what we are dreaming about. On the other hand, eye movement is considered to be secondary to following the hallucinatory images that occur at the time of dreaming. 
Therefore, it is obvious to find that the REM and NREM sleep phases have different brain activity, and although dreams can occur in both phases, it is recognized that approximately 80% of people who wake up in the REM phase achieve remember them, compared to 10% of those who wake up in the NREM phase.  Additionally, a healthy adult person can have approximately four or five REM episodes in one night, which is the estimate of the number of dreams they have. This means that we spend approximately 20% of our sleeping time dreaming. Each REM period, and consequently each sleep, occurs in 90-minute cycles interspersed by periods of NREM phase. It is worth mentioning that these sleep periods can initially be 5 minutes and extend throughout the time we sleep, being longer at the end of the night. 
Biochemically, it can be considered that dreams are caused by a complex mixture of neurotransmitters where serotonin, norepinephrine and histamine decrease significantly; while acetylcholine and dopamine increase. 
Child development of dreams
The amount of time we sleep is greater at birth, occurring up to 50% of the time we sleep and will decrease as the child grows, being approximately 20% between the ages of 3 and 5, a figure very similar to that of adults.  However, 20% of children under 7 years of age report having dreamed, contrary to 80-90% of adults. 
In preschool children, dreams are usually static and simple. For example, seeing an animal or thoughts about eating. There is no movement, no social interactions and no inclusion of the dreamer as an active character. There is no episodic or autobiographical memory, perhaps due to the presence of childhood amnesia. They do not report fear or aggression, misfortunes or negative emotions. Here it must be clarified that children who suffer from night terrors, who wake up (in the NREM phase) with intense fear and agitation, are terrifying due to the disorientation of an incomplete awakening.
From the age of 7, dreams become increasingly longer and more frequent, containing feelings and thoughts, acquiring a narrative structure adding episodic and autobiographical memory. 
Importance of dreaming
Dreams are a product of the evolution of sleep and could play a role in creative function by providing a virtual reality model where the brain is preparing for integrative functions such as learning and consciousness. 
The REM phase is important in learning and memory consolidation; In addition, it has been observed that people who have been deprived of this phase tend to have a “rebound” of REM sleep.
Finally, a decrease in this sleep phase has been associated with the presence of certain neuropsychiatric pathologies, which has raised suspicions that this sleep phase plays a vital function in living beings. 
DISORDERS RELATED TO DREAMING.
We can basically mention the presence of nightmares and night terrors.
Nightmares occur in the REM phase, they are unpleasant dreams with generally negative emotions, accompanied by anxiety, fear or terror; and ends in an awakening where the person is completely alert with a vivid recollection of the dream. [6, 7]
They are the result of hyperactivity accumulated during the day and maintained at night, as has been observed in post-traumatic stress disorder and insomnia, combined with impaired fear extinction where fear memories are continually reinforced. These two factors contribute to the nightmare script, such as a maladaptive response to traumatic experiences, childhood adversity, sleep fragmentation (seen in sleep apnea and periodic leg movement disorder), or other psychiatric conditions (such as anxiety and depression). 
On the other hand, night terrors are generated in the NREM phase (usually in the N3 phase) and are awakenings accompanied by fragments of images, but with the presence of a very intense autonomic response (e.g. sweating and palpitations) and there is a delay. to be completely oriented after these events. 
The prevalence of night terrors is close to 40% in children, while in adults it occurs in 10%. You may jump out of bed in response to viewing threatening images. This disorientation can last 5 to 20 minutes, and attempts to fully awaken the person can lead to further confusion and agitation. 
I am Dr. Cecilio Omar Ceballos Zúñiga, specialist in pulmonology and internal medicine[National Institute of Respiratory Diseases (UNAM) and General Hospital of the State of Sonora (UNAM)] and basic training at the Mexicali School of Medicine (UABC) . Co-founder of Breathbaja.
We are members of:
American Academy of Sleep Medicine
Mexican Academy of Sleep Medicine
Mexican Society of Pulmonology and Thorax Surgery
European Respiratory Society
American Thoracic Society
Latin American Thorax Association
Latin American Society of Respiratory Physiology
Mexican Society of Internal Medicine. Mexicali Chapter
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Nir Y, Tononi G. Dreaming and the brain: from phenomenology to neurophysiology. Trends Cogn Sci. 2010; 14(2): p. 88.
American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed.; 2014.
Meurling IJ, Leschziner G, Drakatos P. What respiratory physicians should know about parasomnias. Breathe. 2022; 18.