Dear SPM experts:
One review paper (EEG source imaging, Michel et al,2004)mention that "The quasi-stationarity that underlies the inverse solution algorithm assumes that the net source in the head is zero.The reference adds a constant potential to the recording at every electrode at any instant, leading to a non-zero net source. In order to avoid this violation of the quasi-stationarity, the data matrix has to be centered, i.e. the constant has to be removed. Interestingly, this mathematically corresponds to the calculation of the average reference of the surface potential (Lehmann and Skrandies, 1980). Thus, the average reference is usually automatically calculated in the source localization software."
I want to know how spm cope with this problem? Is average reference automatically calculated in SPM 3D source reconstruction? If the answer is yes, could you tell me the specific processing step which the average reference is automatically calculated.
Thank you very much!!!
Sincerely
Liang Zhou
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