The construction of spatio-temporal functional brain network based on Ising model for EEG classification.

Objective.Functional brain networks (FBN) are important tools for understanding, classifying and analyzing the brain. However, the multi-term features and temporal correlation of individuals are not adequately represented in single-layer and single-scale FBNs, resulting in room for improvement in the classification accuracy and generalizability of FBNs.Approach.Based on the temporal variability and spatial distribution of electroencephalography (EEG), a multi-scale spatio-temporal FBN is constructed on both temporal and spatial scales. Firstly, brain field data aggregation computation. Based on Ising model design the method of brain field data aggregation, represent whole characteristics of brain field with a symbol, and map multiple time series into a symbol sequence. Secondly, autocorrelation calculation between symbol subsequences. Divide sequence into multiple non-overlapping subsequences, compute the autocorrelation between subsequences based on Kronecker Delta, and represent the relationships between the states of the brain over time. Thirdly, spatio-temporal FBN construction. Subsequence are taken as nodes, and symbol sequence correlations are used as link weights, temporal FBN is constructed. Within each node of the temporal FBN, channels are taken as nodes, and functional connectivities of inter-channel time series are used as link weights, spatial FBN is constructed. Finally, the spatio-temporal FBN is applied for EEG classification.Main results. The classification accuracies of the spatio-temporal FBN are up to 99% on fatigue detection, emotion recognition, Parkinson's diagnosis and motor imagery datasets. Thereby, it is verified that the spatio-temporal FBN possesses satisfactory effectiveness, efficiency and generalizability.Significance. The advantages of the spatio-temporal FBN are that the short-term and long-term features of individuals and categories are represented, while enabling universal recognition among different individuals and distinction among different categories.