2023-09-20| R&D

Dreams and Nightmares: the Mysterious Activities of the Brain During Deep Sleep

by Sinead Huang
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Different individuals may sleep for seven to eight hours each night, with approximately one to two hours of that being deep sleep, particularly among young people or those who engage in regular physical activity. This variation in sleep patterns occurs due to the influence of age and physical activity on brain activity during sleep. The remaining three to four hours are typically spent in shallow sleep.

During the remaining time, individuals may enter the Rapid Eye Movement (REM) phase. REM is not the only time when the brain can dream; dreams can occur at other times during sleep as well. However, REM dreams are more likely to be remembered upon waking up. This is often because peculiar thoughts or sensations awaken us during this phase, or because the final hour of sleep is typically dominated by REM. When dreams or alarm clocks wake us up, the dream experience tends to linger into the first few minutes of wakefulness, making it more likely for us to remember the dream. Sharing particularly strange or interesting dreams with others can enhance the memory of the dream.

Related article: FDA Allows Marketing of New Device to Reduce Nightmare-Related Sleep Disturbances in Adults

Scientific Understanding of REM and Dreams

Studying dreams is challenging because people are asleep and cannot directly observe what is happening. Brain imaging does show certain patterns of brain activity associated with dreams and certain sleep stages more conducive to dreaming. However, these studies ultimately rely on self-reporting of dream experiences. Nevertheless, what humans do during sleep may serve multiple purposes.

Basically, based on studies of brain activity, sleep behavior, and consciousness, all mammals, including platypuses and echidnas, are believed to dream to some extent. Their brain activity and sleep stages align somewhat with human REM sleep. Lower-evolved species, on the other hand, do not exhibit this similarity. For example, jellyfish, which lack a brain, do undergo physiological experiences that can be described as sleep based on their posture, stillness, and “awakening” responses to stimuli. However, jellyfish do not experience the physiological and behavioral elements similar to human REM sleep.

In humans, REM occurs every 90 to 120 minutes during the sleep cycle. REM prevents individuals from entering too deep a sleep, making them more alert and less vulnerable to potential threats. Some scientists suggest that dreaming may serve to prevent the brain and body from becoming too cold. During dreams, core body temperature tends to remain higher, making it easier to respond to external cues or dangers upon awakening.

The Importance of REM for the Brain

Studies measuring brain activity with electroencephalography (EEG) demonstrate the crucial role of REM in maintaining normal brain function. Just as deep sleep aids in the physical restoration of the body, dream sleep “cleans” neural circuits. From a molecular perspective, chemicals related to cognition are utilized and metabolized into other substances or absorbed during daily cognitive activity, with deep sleep being the time when these chemicals revert to an unused state.

During subsequent stages of sleep, humans produce more cortisol, commonly known as the stress hormone. The quantity of cortisol may affect the type of memory being consolidated and the types of dreams individuals may have. As sleep duration increases, dreams often become more bizarre and difficult to connect.

Random Thoughts and Reconfigured Emotions

Daytime brain activity influences us and undergoes a process of reorganization and elimination during sleep, which is why we often dream about events from our waking lives. At times, as the brain reconfigures thoughts and emotions to discard, our consciousness allows us to revisit these experiences. Random thoughts and emotions are eventually mixed in strange and fascinating ways, potentially explaining some of the bizarre qualities of dreams. Traumatic events experienced during the day may also trigger nightmares or anxiety-filled dreams during sleep.

Some dreams appear to have predictive qualities or carry strong symbolic meanings. In many cultures, dreams are seen not only as random neurological discharges but as windows into an alternative reality. While scientists have made progress in their scientific understanding of dreams, the psychological and spiritual aspects of dreams remain largely veiled in mystery. Perhaps the brain is inherently attempting to make sense of things. Human society has always sought to interpret random occurrences, constantly searching for the meaning behind events such as the circling of birds and the movement of planets. Dreaming is one of those phenomena that scientists continuously seek to decode. Dreams are captivating, and they may represent the brain’s way of trying to understand and process everyday experiences. Ultimately, dreams remain a mysterious and inspirational realm with much more to discover and explore.

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