NBE Special Seminar: Alex Ossadtchi & Anton Vershovskii
These talks are hosted by the Department of Neuroscience and Biomedical Engineering (NBE).
Time & place: Friday 08 Dec 2017 14:15–15:15 in seminar room F336, 3rd floor, Rakentajanaukio 2 C
Hosts: Risto Ilmoniemi & Lauri Parkkonen (Department of Neuroscience and Biomedical Engineering)
Name: Alex Ossadtchi, Higher School of Economics, Moscow, Russia
Title of talk: Phase shift invariant imaging of coherent sources from MEG data
There is a growing evidence that our behavior is mediated by simultaneous activity of several interacting and simultaneously active cortical networks. In many cases, empirically observed neuronal synchrony is characterized by nearly zero phase lag between the timeseries of coupled neuronal ensembles. Ironically, for a long time this kind of coupling has remained elusive to the non-invasive neurophysiological techniques because of the spatial leakage (SL) effect.
In this talk we will show how it is possible to cope with the SL effect in the MEG data and detect zero-phase coupled networks. We start with the generative model of the cross-spectrum and render the network estimation task as a source estimation problem but in the product space of interacting source topographies. We then use a special projection operation to alleviate the spatial leakage effect and gain uniform performance over the entire range of the mean phase-lag values.
Realistic simulations show that the proposed technique has superior to other methods detector characteristics and indeed performs uniformly over the entire range of the mean phase difference. We will conclude with demonstrating the physiologically feasible results of applying this method to the real MEG dataset recorded during mental rotation of wrist images.
Name: Anton Vershovskii, Ioffe Phys.-Tech. Institute of RAS, Polytechnisheskaya 26, St.-Petersburg, 194021 Russia
Title of talk: Application of radio-optical spectroscopy to the precision scalar and vector measurements of weak magnetic field
Application of methods of radio-optical spectroscopy to the precision scalar and vector measurements of weak magnetic field has resulted in the development of various magnetometric systems using substantially new principles. The present report is devoted to modifications of quantum optically pumped magnetometers, developed in Prof. E.Alexandrov’s lab of Ioffe Physical-Technical Institute of Russian Academy of Sciences, and demonstrating a set of absolutely new features, or new combinations of features. These schemes include: Potassium optically pumped scalar MX magnetometer; Potassium MX-MR scalar magnetometer; Potassium and Cesium vector magnetometers and many others. The perspectives of creating new compact and sensitive optical sensors schemes for using in MEG are also discussed.