Pre-processing of sensor-level data was performed using FieldTrip
(Oostenveld et al., 2011; http://fieldtrip.fcdonders.nl, 20130909
release) running under Matlab v7.14 (The MathWorks). Twenty
minutes of continuous recording were used to apply independent
component analysis decomposition (ICA) using the “runica” algorithm
as implemented in FieldTrip. An automatic approach based on amplitude
and phase statistics of the decomposed MEG signal was used to
identify the strongest components corresponding to biological artifacts