A Combined Independent Component Analysis (ICA)/ Empirical Mode Decomposition (EMD) Method to Infer Corticomuscular Coupling

EEG-EMG coherence has been recently used to investigate the motor system in humans. Typically this is performed by calculating the coherence between a single EEG electrode and a rectified EMG channel. However, there are strong biological reasons to expect that the cortical to muscular communication is many-to-many as opposed to one-to-one. Here we describe the use of independent component analysis (ICA) to find linear combinations of EEG channels and EMG channels separately. Empirical mode decomposition (EMD) is then used to determine intrinsic mode functions (IMFs) that estimated the envelope of the EMG ICs. We demonstrate that at least 2 EEG ICs correspond with EMG IC IMFs with much greater significance that the pairwise EEG-EMG comparison. Moreover, the proposed method successfully untangles the ~10 Hz and ~30 Hz effects of the corticomuscular coupling which are thought to underlie different neural processes. We suggest that the ICA/EMD approach is worthy of further exploration