Alexey Ossadchi will hold an online seminar on "Imaging networks as sources: PSIICOS and beyond"
15th of March at 6 pm (Msk) Alexey Ossadtchi will hold an online seminar on "Imaging networks as sources: PSIICOS and beyond"
Meeting is available by this link.
Neuronal communication is a defining property of functionally specialized brain networks implemented through synchronization between population activities of distinct brain areas. Despite ecological attractiveness, the non-invasive detection of long-range coupling in EMEG data using conventional metrics (such as coherence or phase-locking value) is by definition contaminated by spatial leakage. Methods utilizing the imaginary part of the sensor data cross-spectrum appear useful in coping with the spatial cross-talk of static sources but result in false negatives in cases where true zero-phase coupling exists in the data and will underestimate interactions with phase lags in the vicinity of zero.
Yet, empirically observed neuronal synchrony in invasive recordings indicates that zero or close-to-zero phase lag coupling scenaria are ubiquitous and result from various configurations of interacting neuronal populations including those when brain regions are engaged into bidirectional communication. In this talk I will revisit our novel method that allows us to mitigate the undesired spatial leakage effects and detect zero and near zero phase interactions. The approach is dubbed PSIICOS and is based on the projection operation that operates on sensorspace cross-spectrum and suppresses the spatial leakage contribution but retains the true zero-phase interaction component. Then, the network estimation task can be cast as a source estimation problem defined in the product space of interacting source topographies where each “source” is a dyadic network. I will also describe the preliminary results on developing a data-driven parametric test for significance of the observed zero-phase coupled networks. I will conclude by outlining the pros and cons of the proposed methodology and will describe future directions to further this methodology.