Hallucinations

Hallucinations refer to false sensory perceptions experienced by a person when no external stimuli are present. Hallucinations can involve any of the five senses including sight, sound, taste, smell and touch, as well as proprioceptive, nociceptive and interoceptive sensations. They may be caused by a variety of mental disorders, such as schizophrenia, bipolar disorder and dementia, as well as drug usage and sleep deprivation. Hallucinations are clinically significant because they can provide clues about a person's mental state and help guide treatment for mental illnesses. In addition, research into the phenomenon of hallucinations has led to a better understanding of the brain and how it processes sensory input.