Generally,the experts are not always the experts. They may think they understand what goes on, but if they did, we wouldn't have so many people with conflicting views being called experts. Well that 's what I think, but lets look at what the experts think may be the mechanism by which people may have auditory hallucinations.There seem to be two main theories of how hallucinations in general and auditory hallucinations in particular are generated. One group of ideas uses the psychological model and the other uses the biological model.

Lets consider the psychological model first. One of the explanations for the occurence of auditory hallucinations is linked to the idea of classical conditioning.

Classical conditioning is a psychological phenomenon which was observed by founding fathers (and mothers) of behavioral psychology. Pavlov (one of these founding fathers), while conducting experiments on his dogs observed something very peculiar. Usually when he did experiment son his dogs he would muzzle them and harness them to a wall and then feed them some meat powder. The dogs would then slobber all over the place because of the tantalizing food. Well, one day Pavlov, after many occurences of this routine, Pavlov discovered that the dogs started to salivate when he put on their harness even before he fed them the powdered meat. This was interesting because he thought that the dogs salivated because they had the food in their mouth, but here the dogs were salivating without the food. He then started to discover the laws of classical condiitoning. Classical conditioning states( I'll make this as concise as possible-there are definitions which are pages long out there) that a physiological response can be elicited by a neutral stimulus alone, when that neutral stimulus is paired with a stimulus which would normally elicit that physiological response.

This principle has been applied to the occurrence of auditory hallucinations. It is possible that auditory hallucinations are as a result of an event which would usually be paired with a certain stimuli. An example of this would be that the pairing of the sight of a police car with its blaring lights usually accompanies the hearing of a siren. If this contingency is repeated regularly, a possible occurence in line with this theory is that you may hear the siren at the presentation of a police vehicle with flashing lights even if the siren is not actually on.

Another psychological theory is that auditory hallucinations may be as a result of some pathological seepage of normally unconscious perceptions into the realm of conscious thought at a later time. This has also been a proposed mechanism for how dreams may occur. This theory is intuitively appealing to me because auditory hallucinations are usually sounds of things previously encountered such as familiar voices and sounds encountered during the course of daily activities.

Another theory suggests that auditory hallucinations may be as a result of an abnormally vivid imagery or imagination in hallucinators.

Finally, a theory of hallucinations being an attribution disorder of inner speech has also been suggested. This means that a hallucinating person attributes his own thoughs to be coming from an external source and is not aware that he is the one thinking those thoughts.

Biological models of auditory hallucination have also been proposed and these are related to the psychological models because the symptoms observed in the psychological model are ultimately as a result of some kind of biological process. Psychologists, especially behavioral psychologists just refuse to consider these because (as B.F. Skinner says) they do not matter if we can use external environmental conditions to change behavior in a predictable way. Anyway, bologists also have something to say about the etiology of auditory hallucinations. One of the theories involves a genetic influence. This would entail that the occurrence of auditory hallucinations may be due to some kind of inherited genetic defect which causes them. This hypothesis seems to be supported by the occurence of auditory hallucinations among schizophrenics. Population studies of schizophrenics show that there is a higher probability of schizophrenia in populations that are genetically linked to schizophrenics.

Neuropsychological hypotheses have also been suggested for the source of auditory hallucinations. The brain stem has been implicated in the auditory hallucinations probably because of the similarity of auditory hallucinations to dreams. The brain stem and the hypothalamus are implicated in the control of sleep and dreaming and so may also be involved in auditory hallucination formation. Both dreaming and auditory hallucinations occur when there is decreased external sensory stimuli and are similar to the extent that a person thinks that the sounds that they are hearing are actually happening.

Various brain region abnormalities have been seen during auditory hallucinations (Musalek et al, 1989). In an experiment studying the cerebral blood flow using single photon emission computed tomography(SPECT). They found that there was a decreased activity in the basal ganglia , hippocampus, parahippocampus and amygdala. This supports one theory of auditory hallucinations called Jackson's hypothesis. Jackson suggested that auditory hallucinations are formed as a result of an abnormal disinhibition of the subcortical regions by the upper cortical regions. This just means that the processes required to control our centers for emotional control are inhibited and so our emotional centers have an abnormal increased activity, which may somehow contribute to auditory hallucinations.