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

Abstract

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.

Inflammatory processes and schizophrenia: two independent lines of evidence from a study of twins discordant and concordant for schizophrenic disorders

“…This unexpected finding had led to the hypothesis that nongenetic pathologic processes alter the co-twins’ genetically identical brains in such a way that pathologically different functional changes can develop in the co-twins [32, 33]. It remains an open question, however, whether these functional changes can be linked to aberrancies of the inflammatory response system.…”

Delta Frequency Optogenetic Stimulation of the Thalamic Nucleus Reuniens Is Sufficient to Produce Working Memory Deficits: Relevance to Schizophrenia

“…Importantly, elevated delta correlates closely with the manifestation of the disease itself; increased delta power is observed in SZ patients, but not in healthy “at risk” subjects such as first-degree relatives (14–17). Even in twins discordant for SZ, increased delta power is not observed in the healthy twin (18, 19). This correlation with the disease stands in contrast to the gamma oscillation abnormality in SZ, which is present in relatives that do not have the disease (16, 20, 21).…”

Exploring the limitations of event-related potential measures in moving subjects. Case studies of four different technical modifications in ergometer rowing

“…The data from fourteen single case measures from six different subjects revealed for a standard paradigm (visual oddball task) comparable intraindividual ERPs during rowing and during rest (non-movement condition) in all cases, despite remaining artifacts in the data. EEG parameters and ERP waveforms are genetically determined and show generally a broad range of interindividual differences, but are also remarkably stable over time in adult subjects (Stassen et al, 1998; Weisbrod et al, 2004). This fact (although probably not well known), strongly supports the reliability of the data, because the intraindividual differences were much smaller than the interindividual differences.…”