Seminar Announcement at UCLA

Title: Measuring Functional Connectivity of the Brain from Electrophysiological Signals Speaker: Sergul Aydore (PhD Candidate, University of Southern California) May 28, 2014 12.00pm-12.30pm 740 WESTWOOD PLAZA, CENTER FOR HEALTH SCIENCE ROOM63-360, LOS ANGELES, CA, 90095 Abstract: The rich temporal content of electroencephalography (EEG) and magnetoencephalography (MEG) data allow us to study dynamic functional networks in the human brain. In this talk, I will describe my recent work on understanding theoretical relationships between different interaction measures and development of novel measures to address classical problem of cross-talk in electrophysiological recordings. Coherence and phase locking value (PLV) are widely used measures that can reveal interactions between electrophysiological signals within a frequency range of interest. In this talk, I will describe statistical properties of the PLV and derive its explicit expression for Gaussian signals and show that it is simply a function of the coherence between two signals. I will support the theoretical findings via local field potential data from a visually-cued motor study in macaque and conclude that, for Gaussian data, PLV provides equivalent information to the coherence. However, the limited spatial resolution of EEG/MEG frequently results in cross-talk between different signals which introduces spurious increase in the coherence measures. To overcome this, measures as imaginary coherence (IC), phase lag index (PLI) and lagged coherence (LC) have been proposed. However, none of these considers the effect of interference from sources at other locations in the brain. In the second part of my talk, I will address this problem using a novel measure, partial lagged coherence (PLC) with L1 regularization, as an extension of LC. I will show via realistic simulations that PLC is more robust to cross-talk in the presence of interfering signals than the other measures. Speaker Bio: Sergul Aydore is an Electrical Engineering Ph.D. candidate at the University of Southern California (USC), Los Angeles. She received her B.S. and M.S. degrees in Electrical and Electronics Engineering from Bogazici University, Istanbul. Her research focuses on developing statistical signal processing techniques to investigate functional connectivity of the brain. She is a recipient of Viterbi School of Engineering Doctoral fellowship and was recognized as a 2014 USC Ming Hsieh Institute Ph.D. Scholar. Her poster titled “The Partial Phase Locking Value for Circular Gaussian Processes” was the recipient of the best Ph.D. poster award in the category of Methods and Models in the 18th International Conference on Biomagnetism (BIOMAG 2012). Host: Prof. Itzhak Fried (director of Cognitive Neurophysiology Laboratory)
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