Clinical symptoms of schizophrenia affect reference-independent measures of task-induced EEG alpha asymmetry

Using questionnaires and task-related EEG signals to reveal hindered reappraisal and biased suppression in individuals with high schizotypal traits

Although impaired ability to regulate emotion is commonly reported in schizophrenic patients, the exact pattern of regulation of negative emotions in high-risk individuals remains unclear. In the current study, 26 high-schizotypy individuals paired with 26 controls completed an emotion regulation questionnaire (ERQ) and a laboratory emotion regulation task with electroencephalogram (EEG) recording. Two emotion regulation strategies, namely, reappraisal and expression suppression, were concurrently examined. The late positive potential (LPP) and frontal alpha asymmetry (FAA) were selected as two independent neural indicators of the emotion regulation effect. In the ERQ questionnaire, individuals in the high schizotypy group reported higher habitual use of suppression than the controls. During the emotion regulation task, the high  schizotypy group showed no early LPP reduction in reappraisal compared with the control group and exhibited a general negative FAA pattern (left-biased alpha). In conclusion, we found that individuals with high schizotypy exhibited maladaptive regulation of negative emotions, manifested in hindered reappraisal and biased suppression; this may exacerbate the negative affect of such emotions and further serve as a risk factor for psychosis conversion. Early interventions targeting the regulation of negative emotions may be beneficial for individuals with high schizotypal traits.

Nongenetic pathologic developments of brain-wave patterns in monozygotic twins discordant and concordant for schizophrenia

Evidence from previous studies has suggested that the inter-individual differences in human brain-wave patterns (EEG) are predominantly determined by genetic factors. In particular, the within-pair EEG concordance of monozygotic (mz) twins was found to be typically as high as r = 0.81 across channels and frequency bands, thus being comparable to that between repeated assessments on the same individual with typically r = 0.83. Yet our investigations into mz twins discordant and concordant for schizophrenia yielded a significantly reduced within-pair EEG concordance for both, the pairs discordant for schizophrenia and the pairs concordant for schizophrenia (with concordance for schizophrenia assessed through a syndrome-oriented approach). A multivariate discriminant function of EEG parameters distinguished in a reproducible way between affected and unaffected subjects at an overall performance of >75% correctly classified subjects, while the severity of illness, as derived from EEG-differences between affected and unaffected subjects, was closely related to the severity of illness as provided by psychopathology syndrome scores. Consequently, EEG anomalies associated with schizophrenia and manifested differently in the mz co-twins concordant for schizophrenia are likely the effect of nongenetic, pathologic processes that evolved independently in the co-twins' genetically identical brains once the illness began to progress. The existence of such nongenetic processes would suggest a modification of the standard phenotype-to-genotype search strategies of molecular-genetic studies that aim to link the schizophrenia phenotype to genetic vulnerability factors.

Memory impairment and auditory evoked potential gating deficit in schizophrenia

Impaired sensory gating and memory function were reported in a study of 10 schizophrenic patients and 10 age- and sex-matched normal subjects. The P50 component of the auditory evoked potential was used as an index of gating. Explicit memory was tested with the Wechsler Memory Scale and implicit memory by artificial grammar learning. The schizophrenic patients showed deficits in both verbal paired associate and visual reproduction tasks. They demonstrated impaired implicit learning in color patterns but not letter strings. They also showed impaired P50 sensory gating. Three-dimensional brain mapping revealed a differential distribution of brain potentials in the processing of S1 and S2 at either P50 or N100 in both groups. However, the group difference was not statistically confirmed. In the controls, both implicit letter-string learning and explicit verbal paired associates were positively correlated with N100 gating, suggesting an association of the early attentive component with lexicons. In the schizophrenic patients, color-pattern implicit learning was positively correlated with P50 gating. The modality-specific impairment of implicit learning in schizophrenia may reflect a failure of adaptive filtering on the flooding input from color patterns.

Muscarinic elicitation of EEG asymmetry in freely moving rats

Averaged frequency spectra (0.5-30 Hz) of electroencephalogram (EEG) were studied in six freely moving rats with chronically implanted electrodes in symmetrical areas of somatosensory cortex. Hemispheric asymmetry in spectra of an ongoing EEG was expressed as a power decrease in 15.6-17.2 Hz band on the left hemisphere and as that in 25.2-27.8 Hz band on the right one. Physostigmine subcutaneous (s.c.) injection (0.25 mg/kg) provoked appearance of the significant left brain bias in 4.7-8.6 Hz range of EEG spectra and the right brain bias in 19.3-21.3 Hz band. These physostigmine effects were counteracted by scopolamine (1.5 mg/kg, s.c.) injected 30 min before. It is suggested that a muscarinic component may be involved in the interhemispheric cooperation associated with cortical theta activity in rats.