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.

The aim of this pilot study is to investigate the immediate effects of Automatic Self-Transcending (AST) meditation on the cognitive function, EEG activity and autonomic arousal (Study 1) and characterize the frontal EEG synchrony during resting state, cognitive activity and AST mental states in traditional and wireless EEG's (Study 2). We report the results of three healthy AST meditation volunteers in this case-report study (Case 1 - age = 26 years, meditative practice time = 2 months; Case 2 - age = 39 years, meditative practice time = 6 years; Case 3 - age = 59 years, meditative practice time = 40 years). In study 1, the volunteers performed a protocol with simultaneous recording of EEG and skin conductance while performing the Stroop test (T0), followed by 20 minutes of AST meditation and immediately the same protocol performed at T0 (T1). We analyzed P300 amplitude and latency, as well as test behavioral response and skin conductance activity before and immediately after a single session of AST. In study 2, the same volunteers performed three tasks with eyes closed on two EEG equipment (traditional and wireless): resting state, cognitive activity and one session of AST, each for 20 minutes. We measured the frontal interhemispheric coherence of alpha1 (8-10 Hz) and beta (13-30 Hz) for each condition and EEG type. Our main findings show that there is an immediate beneficial effect after AST meditation at the level of the same individual with different patterns of P300 and skin conductance activity and that AST meditation is marked by an overall increase in the frontal coherence of alpha1 and beta bands, when compared to other mental states. We conclude that 1) there is an immediate effect on cognition and executive control after AST meditation, 2) the frontal interhemispheric coherence of alpha1 and beta bands are increased during AST, and 3) wireless EEG exhibits the same characteristics observed in traditional EEG and therefore can be used to describe cortical dynamics during AST.

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