Weak brain connectivity and causality measures

Abstract

Event Abstract Back to Event Weak brain connectivity and causality measures A. Perovic1*, W. Klonowski2, W. Duch3, Z. Djordjevic1 and A. Jovanovic1 1 Aston University , Wellcome trust laboratory for MEG studies, United Kingdom 2 Polish Academy of Sciences, Lab. Biosignal Analysis Fundamentals, Nalecz Institute of Biocybernetics and Biomedical Engineering, Poland 3 Nicolaus Copernicus University, Department of Informatics, Poland Aim: We are investigating brain connectivity in cases when causality measures become unstable or are close to zero. This is of interest in the BCI based on inner tunes and music. Methods: Two brain loci might be functionally related while majority of local processing is mutually non related. Such relation among the brain signal sources we call weak connectivity. While in case of imagined motor activity brain connectivity patterns are often related to prominent brain signal features engaging larger relative energy, when dealing with high frequency bands related to imagined tunes and music the situation is opposite, becoming elusive for the established connectivity criteria. By their nature these phenomena are related to weak energy features. The recorded brain signals contain other important components, a number of which corresponds to local area processing. This reduces the causality measures values approaching that of level of noise, thus establishing the connectivity patterns by usual means becomes harder or impossible. We are investigating different causality measures behaviour in such situations, showing that some of them differ substantially and propose the alternative method of weak linear dependence, described partially in 1,2,3, which is useful in this context. Results: We established the instability of causality criteria in experiments related to weak connectivity and proposed alternative methods to establish weak connectivity in the case of inner tunes and inner music. Conclusion: We expect that the Weak connectivity pattern is present in a number of brain states involved in cognitive tasks.