Aberrant Functional Organization in Schizophrenia: Analysis of EEG Coherence during Rest and Photic Stimulation in Drug-Naive Patients

Abstract

EEG coherence provides a measure of functional correlations between two EEG signals. The present study was conducted to examine intrahemispheric EEG coherence at rest and during photic stimulation (PS) in 18 drug-naive patients with paranoid schizophrenia and 30 control subjects. Compared with the controls, the schizophrenic patients had significantly higher intrahemispheric coherence of the resting EEG for the delta band, although no significant group differences were found for other frequency bands. EEG analysis during PS showed that the patients also had significantly higher EEG coherence over the left posterior regions. In this study, we also examined the changes in intrahemispheric coherence from rest to the stimulus condition (i.e., PS-related coherence reactivity); the patients were found to show significantly smaller changes, with significant group differences being also confined to the posterior regions in the left hemisphere. These findings provide evidence that schizophrenic patients have abnormal EEG coherence in both resting and stimulus conditions and suggest more diffuse, undifferentiated functional organization within hemispheres. In addition, diminished coherence reactivity suggests a failure of PS-related functional reorganization in schizophrenia.

Electroencephalographic Spectral and Coherence Analysis of Ketamine in Rats: Correlation with Behavioral Effects and Pharmacokinetics

“…However, irrespective of the condition, most studies found a decrease in coherence in schizophrenic patients [32][33][34][35][80][81][82][83][84][85][86] . In contrast, in a few other studies, an increase [30,31] as well as no difference [36] between patients and healthy controls were found. Also, there are some discrepancies between our preliminary results from comparable ketamine experiments in humans and those from our animal study: the EEG power was decreased in the delta-to-beta bands, while gamma power was increased; further, a robust decrease in EEG coherence in alpha and beta bands in contrast to an increase in all other frequency bands was present [87] .…”

“…The EEG was downsampled to 128 Hz, and spectra between 1 and 40 Hz were calculated at a 0.5-Hz resolution for each 2-second epoch. The autospectra of individual electrodes and cross-spectra of selected electrode pairs were obtained for the following frequency bands: delta (1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12-25 Hz), high beta (25)(26)(27)(28)(29)(30) and gamma (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). EEG coherence was derived from autospectral and cross-spectral values for 30 intrahemispheric electrode pairs (F3-C3, F3-P3, F3-P5, F3-T3, F3-T5, C3-P3, C3-P5, C3-T3, C3-T5, P3-P5, P3-T3, P3-T5, P5-T3, P5-T5 and T3-T5 on the left hemisphere, and analogously on the right) and 6 interhemispheric electrode pairs (between electrodes F3-F4, C3-C4, T3-T4, P3-P4, P5-P6 and T5-T6).…”

Topographic aspects of photic driving in the electroencephalogram of children and adolescents

“…Therefore, the normative data about the peculiarities of the profile shape in various cortical areas of healthy children and adolescents are important as controls for clinical studies. The topographic parameters of the normal driving reaction, such as the interhemispheric symmetry of the profiles with some prevalence of the right hemisphere in the occipital areas, their gradual amplitude decrease in the frontal direction with a decrease of intrahemispheric correlation and an increase of the weight of the theta peak, etc., can be compared with those of the patients with regional alterations in cerebral functioning of both an organic and functional nature (14)(15)(16)(17)(18)(21)(22)(23). Our preliminary results obtained for some children suffering from migraine actually demonstrated a pronounced interhemispheric asymmetry in the profile shape not observed in the resting EEG spectra.…”

Lateralized Theta Wave Connectivity and Language Performance in 2- to 5-Year-Old Children

“…For analysis of cortical network connectivity in 2-to 5-year-old children, we performed coherence analysis using a custom child-sized magnetoencephalogram (MEG) system (Kikuchi et al, 2010), because this is a noninvasive technique that provides measures of cortical neural activity on a millisecond time scale. Assessment of coherence can determine the degree of phase locking between activities recorded at different sensors, which have been used in clinical EEG studies (Wada et al, 1998;Kikuchi et al, 2002;Higashima et al, 2007). MEG produces a reference-free signal, and is therefore an ideal tool to compute coherence between two distant cortical rhythms.…”