On average, 6.5 components per subject were
identified. Ocular and cardiac artifacts were mainly identified on the
basis of their correlation with the electrooculogramand cardiac activity.
Such artifacts, and muscle activity, exceeded the normal thresholds of
different statistical properties (variance, skewness, and kurtosis) and
were identified as biological artifacts. ContinuousMEG datawas filtered
from 1 to 30 Hz (two-pass Butterworth filter), and artifactual independent
components were removed. Epochs of 600 ms, starting 100 ms
before stimulus onset and baseline corrected from −100 to 0 ms,
were extracted. Epochs exceeding amplitudes of 3 pT were discarded
from subsequent analyses. On average, 35.6 out of 198 trials were
rejected per subject and condition.