Relations between structural and EEG-based graph metrics in healthy controls and schizophrenia patients

Abstract

Objective: To assess using graph-theory properties of both structural and functional networks in schizophrenia patients, as well as the possible prediction of the latter based on the former. Abnormal structural and functional network parameters have been found in schizophrenia, but the dependence of functional network properties on structural alterations has not been described yet in this syndrome. Experimental design: We applied averaged path-length (PL), clustering coefficient (CLC) and density (D) measurements to structural data derived from diffusion magnetic resonance and functional data derived from electroencephalography in 39 schizophrenia patients and 79 controls. Functional data were collected for the global and theta frequency bands with subjects performing an odd-ball task, both prior to stimulus delivery and at the corresponding processing window. Connectivity matrices were constructed respectively from (i) tractography and registered cortical segmentations (structural) and (ii) phase-locking values (functional). Principal observations: In both groups, we observed a significant EEG task-related modulation (change between pre-stimulus and response windows) in the global and theta bands. Patients showed larger structural PL and pre-stimulus density in the global and theta bands, and lower PL task-related modulation in the theta band. Structural network values predicted pre-stimulus global band values in controls and global band task-related modulation in patients. Abnormal functional values found in patients (pre-stimulus density in the global and theta bands and task-related modulation in the theta band) were not predicted by structural data in this group. Structural and functional network abnormalities respectively predicted cognitive performance and positive symptoms in patients. Conclusions: Taken together, the alterations in the structural and functional theta networks in the patients and the lack of significant relations between these alterations, suggest that these types of network abnormalities exist in different groups of schizophrenia patients.