Illustration de phénomènes électrophysiologiques avec OpenViBE
Résumé
OpenViBE is a free and open-source software platform to easily design BCIs. It can be used, among many other things, to visualize neurophysiological signals in a simple way. This chapter explains step-by-step how to visualize the different signals with the tools offered by OpenViBE, and thus illustrates several neurophysiological signals mentioned in the previous chapters. In particular, this chapter, an illustrative practical one, aims at guiding the user in building OpenViBE scenarios to visualize and understand different neurophysiological signals.
In this chapter, we notably illustrate the following signals : first, artifacts such as electrooculography (EOG), and electromyography (EMG). A first OpenViBE scenario is presented showing the effect of jaw or forehead muscular activity in EEG signals.
Second, occipital alpha activity, typically modified by closing or opening eyes. We show how to observe the signal in the alpha-band, the frequency range of 8-12Hz.
Third, event-related desynchronization (ERD) and event-related synchronization (ERS), that can notably be observed during motor imagery. Another OpenViBE scenario explains to the reader how to plot the actual ERD/ERS signal, with 2D topographic maps of brain activity and a 3D voxel representation using an estimation of the ERD/ERS within the brain volume (and not only on the scalp), using an inverse solution.
Fourth, event-related potentials (ERP). In particular, how to visualize, using OpenViBE, the average ERP known as the P300 from electrodes covering the parietal lobe.
Finally, this chapter illustrates the steady state visually evoked potential (SSVEP) by displaying the spectrum of EEG signals from the visual areas (i.e., occipital channels) of the brain, thus showing the SSVEP evoked by visual stimulations at different frequencies.
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