Hallucinations

• A hallucination is a false perception, usually characterized by a distortion of real stimuli. Auditory hallucinations are when people hear voices or noises that are not actually occurring. The cause of auditory hallucinations is not known, but there are a number of factors and conditions that are associated with this condition. Mental disorders such as schizophrenia often have auditory hallucinations as symptoms, and certain conditions such as drug use or withdrawal may also be plagued by hallucinations.
  
  

Conditions

• There are a long list of conditions which have auditory hallucinations as a possible symptom. Alcohol withdrawal, use of amphetamines or ketamine, narcolepsy, and depression have all been known to cause auditory hallucinations. Other conditions which are more mental and less physical in nature include schizophrenia, dementia and clinical psychosis have been known to sometimes have auditory hallucinations as a symptom.
  
  

Inner Speech Theory

• One theory of auditory hallucinations, specifically for those who suffer from schtzophrenia, is that they are a form of inner speech. This theory focuses on the fact that during a verbal hallucination (imagination of speech when there isn't any), more blood flows to Broca's area--the part of the brain that deals with language and speech. This is suggestive that what the person thinks he is hearing from an outside source is, in reality, speech that is occurring only inside their own head.