Hallucinations

What is Hallucinations?

A hallucination is a perception in the absence of external stimulus that has qualities of real perception. Hallucinations are vivid, substantial, and located in external objective space. They are distinguished from the related phenomena of dreaming, which does not involve wakefulness; illusion, which involves distorted or misinterpreted real perception; imagery, which does not mimic real perception and is under voluntary control; and pseudohallucination, which does not mimic real perception, but is not under voluntary control. Hallucinations also differ from "delusional perceptions", in which a correctly sensed and interpreted stimulus (i.e., a real perception) is given some additional (and typically absurd) significance.

Hallucinations can occur in any sensory modality—visual, auditory, olfactory, gustatory, tactile, proprioceptive, equilibrioceptive, nociceptive, thermoceptive and chronoceptive.

A mild form of hallucination is known as a disturbance, and can occur in most of the senses above. These may be things like seeing movement in peripheral vision, or hearing faint noises and/or voices. Auditory hallucinations are very common in schizophrenia. They may be benevolent (telling the patient good things about themselves) or malicious, cursing the patient etc. Auditory hallucinations of the malicious type are frequently heard, for example people talking about the patient behind his/her back. Like auditory hallucinations, the source of the visual counterpart can also be behind the patient's back. Their visual counterpart is the feeling of being looked or stared at, usually with malicious intent. Frequently, auditory hallucinations and their visual counterpart are experienced by the patient together.

Hypnagogic hallucinations and hypnopompic hallucinations are considered normal phenomena. Hypnagogic hallucinations can occur as one is falling asleep and hypnopompic hallucinations occur when one is waking up.

Hallucinations can be associated with drug use (particularly deliriants), sleep deprivation, psychosis, neurological disorders, and delirium tremens.

The word 'Hallucination' itself was introduced into the English language by the seventeenth century physician Sir Thomas Browne in 1646 from the derivation of the Latin word alucinari meaning to wander in the mind.

Questions and answers on "Hallucinations"

Hi, I m a high-school student taking Human Anatomy & Physiology and I have a question dealing with brain damage to the Occipital Lobe. Can the...

doctor1 MD

Dear
Welcome to HCM
Are you a medical student?
Then you will learn about it in third and fourth year.
It is possible to have hallucinations if...

Read Full Thread   Ask a Doctor Now

Recent questions on  Hallucinations

doctor1 MD

Hi, I m a high-school student taking Human Anatomy & Physiology and I have a question dealing with brain damage to the Occipital Lobe. Can the...

Ask Question
Doctor Image
MD

Hi, I am Dr. Andrew Rynne (Family Physician). I will be guiding you through the process. Please write your question below.

Related Lab Tests
Related Medical Topics