Modality specific neural correlates of auditory and somatic hallucinations

Somatic hallucinations occur in schizophrenia and other psychotic disorders , although auditory hallucinations are more common. Although the neural cor relates of auditory hallucinations have been described in several neuroimag ing studies, little is known of the pathophysiology of somatic hallucinatio ns. Functional magnetic resonance imaging (fMRI) was used to compare the di stribution of brain activity during somatic and auditory verbal hallucinati ons, occurring at different times in a 36 year old man with schizophrenia. Somatic hallucinations were associated with activation in the primary somat osensory and posterior parietal cortex, areas that normally mediate tactile perception. Auditory hallucinations were associated with activation in the middle and superior temporal cortex, areas involved in processing external speech. Hallucinations in a given modality seem to involve areas that norm ally process sensory information in that modality.