Hallucinations are perceptions in a conscious and awake state that are not the result of external stimuli but have the qualities of real perception.
They are, by their nature, incredibly vivid. Most people think of visual hallucinations, but they can affect almost all of our sensory experience.
They can be centred around our five common senses but also our balance, nervous system (pain, pleasure), our understanding of our body and its proportions, temperature and perception of time.
In humans, hallucinations are often the result of the consumption of psychoactive substances such as LSD or dimethyltryptamine (DMT. DMT occurs naturally within the brain in small quantities.
Dr Rick Strassman put forward the theory that the release of DMT from the pineal gland was responsible for near-death experiences.
Hallucinations can also be triggered by a high fever, and the release of DMT could again be a factor in this.