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Towards a Coherent View of Brain Connectivity

Background. The electroencephalogram provides a myriad of opportunities to detect and assess brain function and brain connectivity. Method. This article describes the relationship between local and non-local brain activation and synchrony, and discusses the use of appropriate connectivity measures to study and train functional brain connectivity. Specific connectivity measures are described including coherence, phase, synchrony, correlation, and comodulation. The measures are contrasted and compared in terms of their ability to detect particular aspects of connectivity and their usefulness for neurofeedback training. Results. Connectivity metrics for example EEG data are calculated and shown graphically, to illustrate relevant principles. Conclusion. It is possible to assess brain connectivity and integrated function for both assessment and training, through the use of appropriate metrics and display methods.