Sharp edge artifacts and spurious coupling in EEG frequency comodulation measures

Recent electroencephalogram (EEG), electrocorticogram (ECoG), and local field potential (LFP) observations suggest that distinct frequency bands interact. Numerous measures have been proposed to analyze such interactions, including the amplitude envelope modulation of high frequency activity by the phase or signal of low frequency activity. In this short communication, we describe how abrupt increases or decreases in voltage data may produce spurious coupling in these measures and suggest techniques to detect these effects. (C) 2008 Elsevier B.V. All rights reserved.