Parallel distributed processing neuroimaging in schizophrenia during frontal tasks

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Parallel-distributed processing neuroimaging was studied in normal control, schizophrenic patients with auditory hallucination (AH) and without AH by using MEG (magnetoencephalography) and synthetic aperture magnetometry (SAM) analysis. In the Stroop color word interference task, the total reaction time was set at 650ms with a time window of 20ms in steps of 50ms. Neural activation began in the left posterior parietal-occipital area (150-250 ms post-stimulus), followed by the right prefrontal polar area (250-350 ms), the left dorsolateral prefrontal cortex (DLPFC, 250-400 ms), and the mid-to lower-primary motor area (350-400 ms). Successive and temporally overlapping activation of various cortical regions were successfully estimated with a short 200 ms time interval, contrary to previous PET and fMRI studies. The left DLPFC in patients without AH showed smaller activation than that in the control group. The left DLPFC in patients with AH showed no significant activation. These results were consistent with the hypofrontality hypothesis in schizophrenic patients and showed that dysfunction in the left DLPFC in schizophrenia with AH might be more remarkable than that in schizophrenia without AH. In word generation (Shiritori) task, significant activation in the left DLPFC was estimated in all patients, while not in most of controls. Significant activation in the left posterior superior temporal gyrus (STG) was estimated in most of controls, while not in any patients. These results showed the functional impairment between the linguistic process in the STG and the organization-control process in the DLPFC in schizophrenic patients.