Topographic abnormality of slow cortical potentials in schizophrenia

Abstract

A recent study from our laboratory has provided evidence for the generation of slow potentials occurring in anticipation to task-performance feedback stimuli, in multiple association cortical areas, consistently including two prefrontal areas. In the present study, we intended to determine whether these slow potentials would indicate some abnormality (topographic) in schizophrenic patients, and thus serve as an indication of abnormal association cortex activity. We recorded slow potentials while subjects performed a paired-associates memory task. A 123-channel EEG montage and common average reference were used for 20 unmedicated schizophrenic (mean duration of illness: 11.3 ± 9.2 years; mean number of previous hospitalizations: 1.2 ± 1.9) and 22 healthy control subjects during a visual paired-associates matching task. For the topographic analysis, we used a simple index of individual topographic deviation from normality, corrected for absolute potential intensities. Slow potentials were observed in all subjects. Control subjects showed a simple spatial pattern of voltage extrema (left central positive and right prefrontal negative), whereas schizophrenic patients presented a more complex, fragmented pattern. Topographic deviation was significantly different between groups (P < 0.001). The increased topographic complexity in schizophrenics could be visualized in grand averages computed across subjects. Increased topographic complexity could also be seen when grand averages were computed for subgroups of patients assembled either according to task-performance (high versus low) or by their scores on psychopathological scales. There was no significant correlation between topographic deviation and psychopathology scores. We conclude that the slow potential topographic abnormalities of schizophrenia indicate an abnormality in the configuration of large-scale electrical activity in association cortices.

Interindividual variability in EEG correlates of attention and limits of functional mapping

“…We intended to quantitatively compare the topographic variance across subjects, between activity present in the pre-S2 window, with sensory-related, that is, activity restricted to post-stimulus windows. For that purpose, we used a scalar measure of topographic deviation from group mean, that previously proved to be useful in demonstrating the higher complexity and variability of SP distribution in schizophrenia, obvious at visual inspection (Basile et al, 2004). This measure is a simple quadratic norm, or spatial variance (square root of the mean electrode-by-electrode squared difference between individual and group average), computed after power normalization, to emphasize topography and reduce the influence of absolute voltage differences.…”

Resting EEG deficits in accused murderers with schizophrenia

“…While diffuse and more-localized slow band activity increases have been identified in the resting EEGs of schizophrenic patients (i.e., over the whole cortex, anterior cingulated gyrus, temporal and posterior cortical regions; Mientus et al, 2002; Miyauchi et al, 1990), excess slow band activity appears to be more prominent in the frontal areas (Miller, 1989). It has been proposed that slowing of EEG activity represents greater brain activation which is consistent with findings of increased slow band activity during hallucinations in schizophrenia and heightened creativity in normal controls (Clementz et al, 1994; Miller, 1989), though another interpretation is that frontally pronounced EEG slowing in schizophrenia represents hypofrontality—one of the most prominent and consistent findings in neuroimaging studies of schizophrenia (Basile et al, 2004; Mientus et al, 2002). EEG slowing correlates with reduced cerebral blood flow and glucose utilization in schizophrenia patients (Wuebben and Winterer, 2001), and hypofrontality may be of particular interest in the study of homicidally violent schizophrenia, given the implication of impaired frontal executive processes in both schizophrenia and antisocial and violent behavior separately (Barkataki et al, 2005; Morgan and Lilienfeld, 2000) and PET findings of reduced prefrontal glucose metabolism in murderers (Raine et al, 1997).…”

Machine Learning techniques for the diagnosis of Schizophrenia based on Event Related Potentials

“…It is known that the topography across the scalp was significantly different between schizophrenia and normal control groups (Morstyn et al, 1983; Frantseva et al, 2014). Some authors had investigated the topographic abnormalities of schizophrenia mainly group-based researches (Basile et al, 2004). However, individual patient-level analysis using topographic features has been less explored for schizophrenia.…”