Unconsciousness is a state in which a living individual exhibits a complete, or near-complete, inability to maintain an awareness of self and environment or to respond to any human or environmental

stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...

. Unconsciousness may occur as the result of

traumatic brain injury A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity (ranging from mild traumatic brain injury TBI/concussionto severe traumatic br ...

, brain hypoxia (inadequate oxygen, possibly due to a brain

infarction Infarction is tissue death ( necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from th ...

cardiac arrest Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and poss ...

), severe intoxication with drugs that depress the activity of the central nervous system (e.g., alcohol and other hypnotic or sedative drugs), severe fatigue, pain,

anaesthesia Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), a ...

, and other causes. Loss of consciousness should not be confused with the notion of the psychoanalytic unconscious, cognitive processes that take place outside awareness (e.g.,

implicit cognition Implicit cognition refers to unconscious influences such as knowledge, perception, or memory, that influence a person's behavior, even though they themselves have no conscious awareness whatsoever of those influences. Overview Implicit cognition i ...

), and with

altered states of consciousness An altered state of consciousness (ASC), also called altered state of mind or mind alteration, is any condition which is significantly different from a normal waking state. By 1892, the expression was in use in relation to hypnosis, though there ...

such as

sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

, delirium,

hypnosis Hypnosis is a human condition involving focused attention (the selective attention/selective inattention hypothesis, SASI), reduced peripheral awareness, and an enhanced capacity to respond to suggestion.In 2015, the American Psychologica ...

, and other altered states in which the person responds to stimuli, including

trance Trance is a state of semi-consciousness in which a person is not self-aware and is either altogether unresponsive to external stimuli (but nevertheless capable of pursuing and realizing an aim) or is selectively responsive in following the dir ...

and psychedelic experiences.

Law and medicine

jurisprudence Jurisprudence, or legal theory, is the theoretical study of the propriety of law. Scholars of jurisprudence seek to explain the nature of law in its most general form and they also seek to achieve a deeper understanding of legal reasoning a ...

, unconsciousness may entitle the criminal defendant to the defense of automatism, i.e. a state without control of one's own actions, an excusing condition that allows a defendant to argue that they should not be held criminally liable for their actions or omissions. In most countries, courts must consider whether unconsciousness in a situation can be accepted as a defense; it can vary from case to case. Hence

epileptic seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...

s, neurological dysfunctions and

sleepwalking Sleepwalking, also known as somnambulism or noctambulism, is a phenomenon of combined sleep and wakefulness. It is classified as a sleep disorder belonging to the parasomnia family. It occurs during slow wave stage of sleep, in a state of lo ...

may be considered acceptable excusing conditions because the loss of control is not foreseeable, but falling asleep (especially while driving or during any other safety-critical activity) may not, because natural sleep rarely overcomes an ordinary person without warning. In many countries, it is presumed that someone who is less than fully conscious cannot give

consent Consent occurs when one person voluntarily agrees to the proposal or desires of another. It is a term of common speech, with specific definitions as used in such fields as the law, medicine, research, and sexual relationships. Consent as und ...

to anything. This can be relevant in cases of sexual assault, euthanasia, or patients giving informed consent with regard to starting or stopping a medical treatment.

References

External links

{{Consciousness Consciousness studies Symptoms and signs of mental disorders

Law and medicine

See also

References

External links