Abnormal Low-Gamma Small-World Response After Visual Stimulation in Schizophrenia

Abstract

Schizophrenia can be described as a functional dysconnectivity syndrome that affects the brain’s circuits in a generalized way. Global disconnection in schizophrenia has been manifold described by applying graph theory and quantifying parameters of network connectivity. However, little is known about how sensory stimulation modulates networks in schizophrenia, such as small-worldness during visual processing. In order to address this question, we applied graph theory algorithms to EEG recordings and classified the functional network in the alpha (8–13 Hz) and low-gamma (36–55 Hz) bands of 13 patients with schizophrenia (SCZ) and 13 healthy controls (HC) during the presentation of a visual stimulus. We measured the amplitude of visual-evoked potentials and the number of nodes, edges, mean degree centrality, clustering coefficient, characteristic path length (L), and small-worldness (SW). As expected, patients presented smaller peak amplitudes of evoked-potentials than HC. Interestingly, in contrast to the controls, SCZ did not change their small worldness index during visual stimulation. This implies that schizophrenia-related dysconnectivity has an impact on the ability of the low-gamma network to react to new sensory input. These results provide evidence about a possible electrophysiological signature of the global deficits revealed by the application of graph theory onto the EEG in schizophrenia.