Altered state of consciousness

A mental state that differs noticeably from ordinary waking awareness in perception, thought, emotion, or sense of self. It can arise spontaneously or through sleep, substances, illness, or deliberate practice.

Neural correlates of consciousness: Patterns of brain activity that track conscious experience. Changes in these patterns accompany many altered states, though no single pattern explains them all.
Dream: A sequence of experiences generated during sleep, often involving vivid imagery and emotion. Dreaming alters perception and thought while the sleeper remains largely disconnected from the surroundings.
Wakefulness: A state of being awake, with responsiveness to the environment and potential for conscious experience. Ordinary waking awareness is the reference point from which an altered state is distinguished.
Sleep medicine: The medical field concerned with diagnosing and treating sleep disorders. It examines abnormal sleep states and the experiences that accompany them.
Hard problem of consciousness: The philosophical problem of explaining why physical processes are accompanied by subjective experience. Altered states intensify the question of how changing brain activity yields changing experience.
Attention: The selective prioritization of some information for processing over other information. Shifts in attention can reshape awareness without eliminating consciousness.
Lucid dream: A dream in which the dreamer recognizes that they are dreaming. It combines dreamlike experience with an unusual return of reflective awareness.
Unconsciousness: A condition in which conscious awareness is absent or severely impaired. Altered states usually involve changed experience, whereas unconsciousness involves its loss.
Psychiatry: The medical specialty concerned with diagnosing and treating mental disorders. It distinguishes chosen or transient alterations from symptoms requiring clinical care.
Measurement of consciousness: Methods for assessing conscious experience and responsiveness, especially when verbal report is unavailable. Comparing states requires measures that do not mistake outward behavior for inner experience.

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