Locating voices in space: a perceptual model for auditory hallucinations?
BACKGROUND
Auditory hallucinations are often perceived as being located in external auditory space ("outside the head"), like real auditory perceptions, but in the absence of a speaker or other external stimulus.


METHODS
A selective literature review of the spatial phenomenology of auditory hallucinations and the cognitive neuroscience of locating real voices in external space was undertaken. An auditory-perceptual model of external auditory hallucinations was developed in healthy right-handed subjects using functional magnetic resonance imaging and the presentation of speech in virtual acoustic space.


RESULTS
Karl Jaspers inextricably linked "reality" and "externality" of auditory hallucinations. Although these two properties do not always occur simultaneously in hallucinating patients, the issue of "externality" is important from both a clinical and neuroscientific perspective. In an auditory-perceptual model of auditory hallucinations, association cortex in the left planum temporale is critically involved in the perception of real voices as located in external space. Right-sided voice stimuli are associated with greater neural response in the dominant (left) auditory cortex than left-sided stimuli. Subjects are better at identifying the spatial location of voices presented on the right than on the left.


CONCLUSIONS
The auditory-perceptual model described helps identify candidate brain systems likely to be involved in the pathogenesis of auditory hallucinations in schizophrenia, and is distinct from other models, which use concepts of "internal monitoring" and "inner speech". Its application, in the cognitive neuroscientific investigation of the phenomenology of auditory hallucinations, may shed further light on the mechanisms underlying this distressing experience.
Hunter
Michael D
MD
Sheffield Cognition and Neuroimaging Laboratory, Academic Department of Psychiatry, University of Sheffield, The Longley Centre, UK. m.d.hunter@shef.ac.uk