Final answer:
Hallucinations are profound distortions in a person's perception of reality, often induced by hallucinogenic drugs. These drugs temporarily disrupt communication between neurotransmitter systems in the brain. Examples of hallucinogens include LSD and PCP.
Step-by-step explanation:
A hallucination is a profound distortion in a person's perception of reality. It can be induced by hallucinogens, which are a class of drugs that cause hallucinations. Hallucinogens can be found in some plants and mushrooms or can be man-made. They are divided into two broad categories: classic hallucinogens, such as LSD, and dissociative drugs, such as PCP. While the exact mechanisms by which hallucinogens and dissociative drugs cause their effects are not yet clearly understood, research suggests that they temporarily disrupt communication between neurotransmitter systems throughout the brain and spinal cord.