modulations in scalp EEG, even in situations where local activity measured intracranially shows decreases in power. It is less clear how this analysis would generalize to MEG. Studies that simultaneously measured MEG and scalp EEG have shown that MEG may be less sensitive to frontal theta oscillations than scalp EEG [35,73], possibly explaining why some MEG studies have observed negative theta effects in retrieval success contrasts [21,35].
