Sciences of the mind, such as psychology, neuroscience, psychiatry and philosophy, have been actively asking questions about the nature of consciousness, awareness, perception and sensation. These questions are particularly poignant when we think about sleep. During sleep, our bodies seem passive and our minds appear disconnected from the outside world. Yet in dreams, we experience realistic scenarios, complex emotions and even learn new things. Experiences during sleep can change our view of ourselves, have transformative spiritual power, engage our imagination, our senses and let us experience our sense of self as flexible, playful and creative.
At first glance, there are dramatic differences between wakefulness and sleep. When we look at someone sleeping, they appear to us passive and unresponsive. Behind closed eyes and relaxed bodies, however, is hidden a complex reality of many physiological and psychological processes that are going on during sleep, including a wide variety of conscious experiences, such as dreams, nightmares, sensations, thoughts, and perceptions. Contemporary science of sleep and dreams has revealed that during sleep our minds are busy stabilizing new memories and integrating them into the networks of memories and knowledge, that our brains reorganize, our bodies recharge, and our minds work out different ways to make sense of our daytime lives. There are physiological processes, such as removal of toxic products of brain metabolism, or secretion of certain hormones, that only happen during sleep. Similarly, psychological processes, such as stress management, emotion regulation and memory consolidation also need sleep. We now know that during sleep our bodies and our minds are actively engaging in this variety of tasks.
Sleep is for memories and emotions
Perhaps one of the most researched functions of sleep is that of memory consolidation and integration. Our brains are plastic and are constantly changing based on the experiences that we are having and on skills that we practice. During sleep, experiences that we have had during the day are integrated: some are forgotten, some are strengthened, and some are nuanced. When we are unconscious and not engaging with the outside world, our internal worlds are being re-created. How exactly the mind chooses which memories to keep and which to forget, is still a mystery, but it appears that memories that are associated with emotions, both positive and negative, are most likely to be strengthened during sleep. Without sufficient sleep we lose our ability both to learn and to remember, and positive experiences suffer most: we are most likely to perceive the world as more negative and threatening, and to remember more negative experiences when we are sleeping too little. Even short periods of sleep during daytime naps appear beneficial for memory consolidation and for emotion regulation.
Sleep keeps us dynamically in sync with the world around us
Despite much knowledge of the relationship between sleep and wakefulness, it is still not known what exactly the ideal human sleep should be: how long should we sleep, what is the best sleeping environment, is it better to sleep alone or with others. Our circadian system is both robust (has its own internal rhythm, that persists on its own) and flexible (can adapt, over time, even to most dramatically changing circumstances). First of all, we adapt to planetary cycles. The most obvious cycle is the cycle of day and night—when it gets dark our brains release a hormone, melatonin, that tells our whole body that it is now time to sleep, and sunlight has a power to tell our brains and bodies to be awake. Which is why most of our sleeping-waking cycles are approximately 24 hours long. However, if we live in environments that have a different length of day (polar night, space, underground caves, for example), our cycles may also change and become non 24-hour long. Our bodies adapt to changes in seasons—we sleep longer during winter months, and to changes in time zones—we are able to shift our internal rhythms to fit the new environments when we travel far.
Second, we adapt to the social rhythms of our lives that dictate when the right time is to get up, when we eat, when we are active, and when we rest. These social pressures may go against our natural tendencies: some people are more comfortable waking up late and going to bed late, and the social pressures can be disruptive to their abilities to get good sleep. With discipline and regularity, we can mostly adapt to these social cycles: our circadian system has a natural tendency we are born with (whether we prefer mornings or evenings), and a capacity to be entrained to physical and social demands and pressures of the external world. Still, it appears that discovering these natural tendencies – chronotypes – helps work out a rhythm that best suits an individual. Finding this balance between social life and biological individual predispositions appears essential for good health.
Lastly, it appears that across the world people have very different sleeping habits: some sleep alone or with partners in quiet bedrooms, others sleep in the same room or sometimes the same bed with children, pets, and other family members. These cultural variations are more than preferences, these are entrained patterns of how we relate to sleep, what makes us relax and rest. Solitary sleep may be preferable to some individuals, while others learn to feel secure in presence of others. Quiet environments promote deep sleep in some people, but noisy environments are reassuring for some others. Sleep behaviours therefore are dynamic, learned, adaptable habits that have a biological component (chronotype, how much sleep we need), planetary component (daytime-nighttime alternation, season change), and social practices component (when, where and how we sleep).
Dreams help us make sense of life
In sleep, our memories are strengthened, and our emotions are regulated, but what role do dreams play in this process? While it would be logical to assume that dreams may represent some of the processes of memory consolidation during sleep, if we pay careful attention to dream content, we will see that dreams almost never replay memories, instead, dreams remix different memory sources (people, places, activities) into novel, creative scenarios. One possibility is that while sleep with little dreaming may be beneficial for strengthening memories, in other words, making them more discrete, dreaming shakes up some of these connections to ensure that our memory system is flexible. Some scholars would say that dreams function creatively, through associations, to make sense of lived experiences and to contextualize and integrate emotions. In this way, dreams are not merely illusory experiences that fool us into believing in false reality, instead, dreams can be seen as metaphorical reflections of our emotional psychic lives that let us creatively explore our subjective life and playfully try out being in different contexts and even being different selves.
Dreams are skills that we can learn
In the past, Western science thought of dreams as passive experiences, something that happens to the dreamer without their involvement. However, it is clear that dreams can be understood as skills, as something that we can learn. And that is true in at least two ways: first, by paying attention to dreams during waking hours (keeping a dream diary, sharing dreams, listening to other people’s dreams, interpreting dreams), we can learn to remember more dreams, our dreams become more vivid, immersive and detailed. This happens because our cognitive skills, such as attention, introspection, ability to notice one’s own states of mind, are transferable between states of consciousness, between waking and dreaming. Second, it is possible to learn to recognize the dream state as the dream state, and learn some degree of control, agency during dreaming. We call this phenomenon lucid dreaming, and many cultures have their own names for it, such as the dream yoga in Tibetan Buddhist tradition. Learning lucid dreaming can be a way to familiarize oneself with one’s own mind, practice contemplation, and even cure nightmares, get rid of bad dreams, and increase wellbeing.
Dreamers are not disconnected from the world
During sleep, our brains temporarily paralyze our bodies so that we do not act out our dreams. This fact has led scholars to believe that dreams are produced completely by the brain without any contribution of the body or of the environment. However, that does not seem to be the case. Sensations from the outside world—smells, sounds, lights, touch—can make their way into the dream and change it. Sensations from one’s own body—pain, discomfort, temperature—can also incorporate into dream scenario. The most curious thing about those incorporations is that those are rarely experienced as direct, and most often are somehow transformed, distorted, changed into something else. For example, a sensation of pressure on a leg may get transformed into an image of a dream character walking funny. This means that even during sleep, we maintain a connection to our bodies and to the outside world, and that sensations that are not interpreted by our minds as necessitating awakening, are incorporated, creatively, into the ongoing dream. Such experiences confirm some of our current ideas about the mind: that the mind is embodied, enactive and extended into the world. The fact that our senses can be interpreted metaphorically by our brains in sleep poses an intriguing question: does this also happen during wakefulness? Thus, the creative and associative way in which our dreaming minds interpret the outside world and bodily sensations, shows that processes of imagination and of making sense of experiences may be constantly and creatively active, whether we are asleep or awake.
