Disordered brain functional connectivity during hallucinations in a schizophrenic patient

We have previously used PET to identify the neural correlates of hallucinations in schizophrenic patients, including a 23 year old, drug-naive patient with visual and auditory hallucinations. The objectives of this study were to identify the brain areas negatively correlated with this latter patientʹs hallucinations, and to compare this pattern of distribution with that of his (previously described) positive correlations. The patient was scanned, with eyes closed, using low dose/high-sensitivity 3-D H215O PET in two multi-scan study sessions. An event-related count rate correlational analysis (developed for this purpose, and validated) was performed to identify brain areas in which activity correlated specifically with symptom occurrence (p<0.01). PET-MRI coregistration was performed. Brain areas negatively correlated with hallucinations included R superior temporal gyrus, R posterior cingulate gyrus, L striatum, bilateral prefrontal cortices, and primary visual and auditory cortices. Brain areas positively correlated with hallucinations included L superior temporal gyrus, L posterior cingulate gyrus, R striatum, and visual and auditory association cortices. During hallucinations, inverse relationships of brain activity were therefore observed between contralateral homologous cortical structures, contralateral homologous subcortical structures, ipsilateral cortical and subcortical structures, prefrontal and post-rolandic association cortices, and primary and association sensory cortices. These symptom-specific reciprocal patterns suggest a lack of integration at the systems level, and are consistent with other recent findings of abnormal interactions among brain regions in schizophrenia. Disordered functional connectivity in the brain regions noted here may contribute to the misinterpretation of internally-generated sensory representations characteristic of schizophrenic hallucinations.