Dimensional complexity of EEG waveforms in neuroleptic-free schizophrenic patients and normal control subjects.

Dimensional complexity reflects the number of independent variables contributing to a dynamic process. EEG epochs recorded from 12 neuroleptic-free schizophrenic patients and 11 normal control subjects were Laplacian-filtered to highlight activity specific to prefrontal and parietal areas, and dimensional complexity measures of the resulting signals were then derived. Complexity of EEG waveforms generated by schizophrenic patients was depressed relative to that of normal subjects, especially in left frontal and right parietal regions. These data suggest that complexity of underlying is also reduced.

EEG coherence of prefrontal areas in normal and schizophrenic males during perceptual activation.

Multiple studies have demonstrated prefrontal dysfunction among schizophrenics. The prefrontal cortex does not function in isolation, but instead relies on extensive connections with other brain areas. Functional relationships between cortical areas were assessed by calculating the coherences between different scalp electroencephalogram (EEG) signals recorded from 13 unmedicated male patients with schizophrenia and 9 normal male subjects. Alpha-band coherences linked to prefrontal areas in schizophrenic patients were about the same as those of normal controls when subjects were cognitively "at rest," but they were reduced for certain electrode pairs in the former group when performing the degraded-stimulus continuous performance test. Most of these findings were not accounted for by changes in alpha power, suggesting that "cortical circuits" extending beyond prefrontal areas may be disrupted in schizophrenia.

Effect of attention on frontal distribution of delta activity and cerebral metabolic rate in schizophrenia.

15 patients with schizophrenia and nine normal volunteers had 32 channel topographic EEG recorded for spectral analysis during the uptake of 18-F-deoxyglucose (FDG) for positron emission tomography (PET). Both patients and controls performed the Continuous Performance Test, a visual vigilance task, during FDG uptake. EEG was also obtained during an initial pre-FDG resting period. Each EEG epoch was individually inspected for eye movement artifacts. Analysis confirmed increased delta activity in the frontal region of patients with schizophrenia in comparison to normal controls, and a significant correlation between increased frontal delta and relative reduction in frontal lobe metabolism among patients with schizophrenia. This finding of increased delta is consistent with PET, blood flow and topographic EEG studies of schizophrenia, suggesting reduced frontal activity.