A FUNCTIONAL NEUROANATOMY OF HALLUCINATIONS IN SCHIZOPHRENIA

HALLUCINATIONS, perceptions in the absence of external stimuli, are pr ominent among the core symptoms of schizophrenia. The neural correlate s of these brief, involuntary experiences are not well understood, and have not been imaged selectively. We have used new positron emission tomography (PET) methods(1,2) to study the brain state associated with the occurrence of hallucinations in six schizophrenic patients. Here we present a group study of five patients with classic auditory verbal hallucinations despite medication, demonstrating activations in subco rtical nuclei (thalamic, striatal), limbic structures (especially hipp ocampus), and paralimbic regions (parahippocampal and cingulate gyri, as well as orbito-frontal cortex). We also present a case study of a u nique, drug-naive patient with visual as well as auditory verbal hallu cinations, demonstrating activations in visual and auditory/linguistic association cortices as part of a distributed cortical-subcortical ne twork. Activity in deep brain structures, identified with group analys is, may generate or modulate hallucinations, and the particular neocor tical regions entrained in individual patients may affect their specif ic perceptual content. The interaction of these distributed neural sys tems provides a biological basis for the bizarre reports of schizophre nic patients.