Modeling Dependence in a Network of Brain Signals

Start: 11/03/2011 - 4:15pm
End  : 11/03/2011 - 5:15pm

Statistics/OR/Math Finance Seminar

Hernando Ombao (Department of Biostatistics, Brown University)


In this talk, we shall discuss methods for characterizing dependence between brain regions. My own interest in this area stems from a growing body of evidence suggesting that various neurological disorders, including Alzheimer’s disease, depression, and Parkinson’s disease may be associated with altered brain connectivity. Dependence may be portrayed in a number of ways. This talk will be focused on measures that depict interactions in oscillations between brain regions. We discuss basic coherence measures and develop more comprehensive measures of coherence that capture complex dependence structures in brain signals. The classical notion of coherence pertains only to contemporaneous single-frequency interactions between signals. To generalize this notion, we introduce the time-lagged dual-frequency coherence which measures, as a specific example, oscillatory interactions between alpha activity on a current time block at one electroencephalogram channel and beta activity on a future time block at another channel. We develop formal methods for statistical inference under the framework of harmonizable processes. This new approach will be applied to analyze an electroencephalographic data set to investigate dependence between the visual, parietal and pre-motor cortices under the context of a visual-motor task. This is joint work with PhD students Mark Fiecas and Cristina Gorrostieta and neuroscience collaborators at Brown and MGH. BRIEF BIOGRAPHY Hernando Ombao is Associate Professor of Biostatistics at Brown University. His work includes theory and methods for non-stationary time series and their applications to brain science. He was born and raised in the Philippines and came to the United States to pursue graduate education. He earned his M.Sc. degree in Statistics at UC-Davis and Ph.D. degree in Biostatistics from the University of Michigan. Prior to Brown, he held faculty positions at the University of Pittsburgh and the University of Illinois. He will be joining the Department of Statistics at UC Irvine effective the Winter Quarter of 2012. He serves as Associate Editor for the Journal of the American Statistical Association (JASA) and the Journal of the Royal Statistical Society Series B (JRSS-B).

Millikan 213, Pomona College