Transition to and from sleep may be attended by a wide variety of sensory experiences. These can occur in any modality, individually or combined, and range from the vague and barely perceptible to vivid hallucinations. Sights Among the more commonly reported, and more thoroughly researched, sensory features of<unk>  are phosphenes which can manifest as seemingly random speckles, lines or geometrical patterns, including form constants, or as figurative (representational) images. They may be monochromatic or richly coloured, still or moving, flat or three-dimensional (offering an impression of perspective). Imagery representing movement through tunnels of light is also reported. Individual images are typically fleeting and given to very rapid changes. They are said to differ from dreams proper in that<unk>  imagery is usually static and lacking in narrative content, although others understand the state rather as a gradual transition from<unk>  to fragmentary dreams, i.e., from simple Eigenlicht to whole imagined scenes. Descriptions of exceptionally vivid and elaborate<unk>  visuals can be found in the work of Marie-Jean-Léon, Marquis d'Hervey de Saint Denys. Tetris effect People who have spent a long time at some repetitive activity before sleep, in particular one that is new to them, may find that it dominates their imagery as they grow drowsy, a tendency dubbed the Tetris effect. This effect has even been observed in amnesiacs who otherwise have no memory of the original activity. When the activity involves moving objects, as in the video game Tetris, the corresponding<unk>  images tend to be perceived as moving. The Tetris effect is not confined to visual imagery but can manifest in other modalities. For example, Robert Stickgold recounts having experienced the touch of rocks while falling asleep after mountain climbing. This can also occur to people who have travelled on a small boat in rough seas or have been swimming through waves, shortly before going to bed, and they feel the waves as they drift to sleep, or people who have spent the day skiing who continue to "feel snow" under their feet. People who have spent considerable time jumping on a trampoline will find that they can feel the up-and-down motion before they go to sleep. Many chess players report the phenomenon of seeing the chessboard and pieces during this state. New employees working stressful and demanding jobs often report feeling the experience of performing work-related tasks in this period before sleep. Sounds<unk>  hallucinations are often auditory or have an auditory component. Like the visuals,<unk>  sounds vary in intensity from faint impressions to loud noises, like knocking and crash and bangs (exploding head syndrome). People may imagine their own name called, crumpling bags, white noise, or a doorbell ringing. Snatches of imagined speech are common. While typically nonsensical and fragmented, these speech events can occasionally strike the individual as apt comments on—or summations of—their thoughts at the time. They often contain word play, neologisms and made-up names.<unk>  speech may manifest as the subject's own "inner voice", or as the voices of others: familiar people or strangers. More rarely, poetry or music is heard. Other sensations Gustatory, olfactory and thermal sensations in<unk>  have all been reported, as well as tactile sensations (including those kinds classed as paresthesia or formication). Sometimes there is synesthesia; many people report seeing a flash of light or some other visual image in response to a real sound. Proprioceptive effects may be noticed, with numbness and changes in perceived body size and proportions, feelings of floating or bobbing as if their bed were a boat, and out-of-body experiences. Perhaps the most common experience of this kind is the falling sensation, and associated hypnic jerk, encountered by many people, at least occasionally, while drifting off to sleep. Cognitive and affective phenomena Thought processes on the edge of sleep tend to differ radically from those of ordinary wakefulness. For example, something that you agreed with within a state of<unk>  may seem completely ridiculous to you in an awake state.<unk>  may involve a "loosening of ego boundaries ... openness, sensitivity, internalization-subjectification of the physical and mental environment (empathy) and diffuse-absorbed attention."<unk>  cognition, in comparison with that of normal, alert wakefulness, is characterized by heightened suggestibility, illogic and a fluid association of ideas. Subjects are more receptive in the<unk>  state to suggestion from an experimenter than at other times, and readily incorporate external stimuli into<unk>  trains of thought and subsequent dreams. This receptivity has a physiological parallel; EEG readings show elevated responsiveness to sound around the onset of sleep. Herbert Silberer described a process he called autosymbolism, whereby<unk>  hallucinations seem to represent, without repression or censorship, whatever one is thinking at the time, turning abstract ideas into a concrete image, which may be perceived as an apt and succinct representation thereof. The<unk>  state can provide insight into a problem, the best-known example being August Kekulé’s realization that the structure of benzene was a closed ring while half-asleep in front of a fire and seeing molecules forming into snakes, one of which grabbed its tail in its mouth. Many other artists, writers, scientists and inventors – including Beethoven, Richard Wagner, Walter Scott, Salvador Dalí, Thomas Edison, Nikola Tesla and Isaac Newton – have credited<unk>  and related states with enhancing their creativity. A 2001 study by Harvard psychologist Deirdre Barrett found that, while problems can also be solved in full-blown dreams from later stages of sleep,<unk>  was especially likely to solve problems which benefit from hallucinatory images being critically examined while still before the eyes. A feature that<unk>  shares with other stages of sleep is amnesia. But this is a selective forgetfulness, affecting the hippocampal memory system, which is responsible for episodic or autobiographical memory, rather than the neocortical memory system, responsible for semantic memory. It has been suggested that<unk>  and REM sleep help in the consolidation of semantic memory, but the evidence for this has been disputed. For example, suppression of REM sleep due to antidepressants and lesions to the brainstem has not been found to produce detrimental effects on cognition.<unk>  phenomena may be interpreted as visions, prophecies, premonitions, apparitions and inspiration (artistic or divine), depending on the experiencers' beliefs and those of their culture.
Hypnagogia
Piquerism
Food craving
Hedonic hunger
Emotional eating
Gigantism
Compensatory hyperhidrosis
Facial toning