Predicting EEG responses using MEG sources in superior temporal gyrus reveals source asynchrony in patients with schizophrenia

OBJECTIVE

An integrated analysis using Electroencephalography (EEG) and magnetoencephalography (MEG) is introduced to study abnormalities in early cortical responses to auditory stimuli in schizophrenia.

METHODS

Auditory responses were recorded simultaneously using EEG and MEG from 20 patients with schizophrenia and 19 control subjects. Bilateral superior temporal gyrus (STG) sources and their time courses were obtained using MEG for the 30-100 ms post-stimulus interval. The MEG STG source time courses were used to predict the EEG signal at electrode Cz.

RESULTS

In control subjects, the STG sources predicted the EEG Cz recording very well (97% variance explained). In schizophrenia patients, the STG sources accounted for substantially (86%) and significantly (P<0.0002) less variance. After MEG-derived STG activity was removed from the EEG Cz signal, the residual signal was dominated by 40 Hz activity, an indication that the remaining variance in EEG is probably contributed by other brain generators, rather than by random noise.

CONCLUSIONS

Integrated MEG and EEG analysis can differentiate patients and controls, and suggests a basis for a well established abnormality in the cortical auditory response in schizophrenia, implicating a disorder of functional connectivity in the relationship between STG sources and other brain generators.

Spontaneous brain magnetic activity in schizophrenia patients treated with aripiprazole

This magnetoencaphalographic (MEG) study was conducted as part of a multicenter clinical trial to study the efficacy of aripiprazole. Participants included 5 DSM-IV schizophrenia subjects and 10 age-matched normal controls. The schizophrenia subjects underwent a second MEG recording after 8 weeks of open-label treatment with aripiprazole. Overall, control subjects showed no abnormal spontaneous magnetic brain activity. At washout, 3 patients showed increased delta and theta activity along with paraxosymal bitemporal slow waves. In 2 of these patients, the slow waves were generated in the superior temporal plane, as determined by dipole modeling. In the third patient, the slow waves appeared to have been generated at multiple regions throughout the temporal and inferior parietal lobes. As a group, schizophrenia patients, when compared with normal controls, demonstrated significant decreases in alpha peak frequency and power. Following treatment, aripiprazole had a significant normalizing effect on delta and theta activity. Patients on aripiprazole continued to demonstrate significant abnormalities in alpha frequency and power.