Study On Functional Brain Network Of Schizophrenia Auditory Gating Based On Granger Causality

ObjectiveSchizophrenia is a serious disorder of mental disorders,studies have shown that abnormal connections between brain regions,disturbed oscillatory activity and synchronization changes are significant features of schizophrenia.In order to study the state of brain network connection in patients with schizophrenia during the information exchanges in the gating process,this paper analyzes the causal connection characteristics of EEG signals in the gating process under the condition-test paradigm using the frequency based Granger causality technique.The quantitative analysis of the global and local network connection characteristics of schizophrenic patients was applied on a particular frequency band using graph theory parameters during the gating process.This paper also explored that whether there exists a specific brain network benchmark to assess the clinical diagnosis and treatment of schizophrenic patients as well as to provide a theoretical and technical support for the quantitative analysis of schizophrenia brain function.MethodsBased on the 32-channel EEGs in the conditional-test paradigm,the causal connection matrix of the two groups of subjects were calculated by the DTF method based on Granger causality analysis.Quantitative analysis of the differences in the connection characteristics between two groups of subjects was performed by constructing a brain function matrix.Bellows are the method procedures:（1）Experimental data: 20 schizophrenic patients and 20 normal subjects were enrolled for the EEG by the auditory condition-test paradigm.（2）Preprocessing the 32-channel EEGs data so to remove noise and artifacts such as line noise and baseline drift.（3）The causal connection network is constructed using the direct transfer function method by the frequency based Granger causality to calculate the causal connection matrix from channel j to channel i.（4）The average causal connection intensity of the whole brain and the causal IV connection within and between the brain regions of the frontal,central and parietal area were calculated.（5）The causal network evaluation parameters such as the coefficient of aggregation and global efficiency of two groups were computed;（6）The information flow gain of the whole brain was calculated and the spatial distribution of information flow gain was presented;（7）The rich-club coefficients of the two groups were used to determine whether there is a rich-club feature.Results 1.The average causal connection at each frequency band In the High-beta and Gamma bands,the DTF_mean in the SZ group was significantly higher than the HC group.2.The average causal connection at different brain regionsThe DTF connection of the High-beta and Gamma bands in the SZ group is significantly larger than the HC group in the connection between the central and central areas to the top area.For the connection between the central area and the frontal area,the DTF connection of SZ group was significantly higher than the HC group’s.SZ group showed that the connection within the parietal area at theta and Alpha bands were significantly higher than the HC group.3.Quantitative analysis of causal networksIn the High-beta and Gamma bands,the coefficient of aggregation of the SZ group was significantly higher than the HC group,and the global efficiency of the SZ group was significantly higher than that of the HC group.4.Information flow gain at each frequency bandThe gain of the information flow near the PO₃ channel in the SZ group was lower than the HC group,while the gain value of the Cz channel in the SZ group was higher than the HC group.The information flow gain of the FZ channel of the SZ group becomes larger along with the frequency increasing.5.Rich-club coefficientBoth SZ group and HC group had rich club characteristics.The rich-club coefficients of SZ group were significantly lower than HC group except for High-beta band.ConclusionIn the auditory sensory gating inhibition process,the brain causal network under the high beta and gamma bands has an over-connected phenomenon,which may be a reason for schizophrenic patients who are unable to perform the sensory gated inhibition.There exists an abnormality in the connection between the brain regions of the schizophrenic patients,suggesting that the abnormal causal network connection of the schizophrenic subjects is mainly in the central and central to the parietal and frontal regions.The coefficient of aggregation and global efficiency of the schizophrenic subjects were significantly higher in the high-beta and gamma bands than in the normal subjects.This indicates that the local and global connectivity parameters of the brain network were increased in the high frequency band.Schizophrenia patients during the auditory sense of gated inhibition process is unable to effectively distinguish between the effective and interference information from the outside world.Some brain areas were disturbed by the interference,the complex network characteristics becomes abnormal.Studies on Information flow gain have found that information flow activity at the Cz channel as well as the high frequency segment at the front area for schizophrenic subjects were increased while the flow of information at the parieto-occipital area were decreased.The rich-club coefficient of the network was found that both schizophrenic patients and normal subjects had rich club characteristics which indicates that nodes with large degree tends to connect closer to each other in the network.