Multimodal neuroimaging in schizophrenia: a systematic review of EEG and fMRI integration.

Schizophrenia (SCZ) is a complex psychiatric disorder involving disruptions in neural signaling and neurovascular function that are incompletely characterized by single-modality imaging. This systematic review evaluates how concurrent electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can advance understanding of brain dynamics underlying SCZ, focusing on neurovascular coupling and large-scale network abnormalities. A systematic search of three online databases identified 16 English-language studies of individuals with SCZ or related psychosis spectrum conditions using simultaneous EEG-fMRI. Inclusion criteria covered original research reporting relationships between electrophysiological (Event-Related Potentials, oscillatory) events and fMRI-derived Blood Oxygen Level-Dependent signals, with clinical or cognitive endpoints. EEG findings implicate impaired sensory gating and cognitive processing, including abnormal P50 suppression, reduced P300 amplitudes, and dysregulated gamma and beta oscillations. fMRI results demonstrate reduced activity and altered network connectivity, notably within the default mode network. Recent studies suggest altered fMRI responses to EEG events, raising the hypothesis of neurovascular decoupling. However, methodological heterogeneity limits interpretation, and findings should be regarded as hypothesis-generating rather than conclusive. In summary, concurrent EEG-fMRI provides valuable insights into neural and neurovascular disruptions in SCZ. Advancing this field will require standardization and large-scale, reproducible studies to translate multimodal findings into clinical biomarkers and novel therapies.