Variability is the rule: Neurophysiology and contextual visual processing in schizophrenia

Traditionally, studies in schizophrenia research employ a single experimental paradigm. The results typically demonstrate a significant difference between patients and controls. Subsequent studies aim to describe the underlying abnormal mechanism at the genetic and neurobiological levels. While this approach has driven tremendous advancements in the field, research over the past twenty years suggests that it may not entirely capture the complexity of schizophrenia. New research methodologies are needed to systematically investigate the intricate nature of the disorder. Here, I utilized resting-state electroencephalogram (EEG) and visual paradigms to delve into the complexity of neurophysiology and contextual visual processing in schizophrenia.Initially, I demonstrate that various features extracted from resting-state EEG, such as beta band power or connectivity measures, exhibit weak correlations with each other, despite significant group differences between patients and controls. I show that some of these features remain remarkably stable over several years, indicating that measurement error cannot entirely account for these low correlations and that variability might reflect genuine individual differences. These findings raise critical questions about the nature and interpretation of significant results in schizophrenia research and advocate for research methodologies that systematically examine a large range of features. Furthermore, I present EEG and behavioral results suggesting that this issue extends to fields beyond schizophrenia research. I propose different scenarios to explain these puzzling results and suggest strategies to cope with this vast variability. Additionally, I present behavioral results using visual (un)crowding experiments to probe contextual vision in schizophrenia. In (un)crowding, the processing of a visual target is influenced by flankers. I demonstrate that in variations of this paradigm, the same patients exhibited intact and deficient contextual processing compared to controls, raising questions about the generalizability of results obtained using a single experimental paradigm to investigate general abnormal mechanisms. Moreover, I provide neurophysiological evidence for alterations in predictive coding processes in schizophrenia, potentially contributing to alterations in contextual vision and other complex aspects of perception and psychopathology in patients.