Greetings fellow imagers–
The Eklund group showed with resting data that false positive rates are not well contained when traditional assumptions are made about the spatial smoothness of BOLD fMRI data when block-based analyses are conducted–and that this is less so for event-related analyses. This leads us to ask about the implications for resting fMRI connectivity analyses. It’s challenging to apply the logic of Eklund et al. in this case because their approach hinges on finding spurious block / event-related effects in resting data (NB: there is room here for speculation about natural fluctuations in thinking/emoting that could account for what Eklund considers spurious effects). Specifically, we can’t apply the Eklund approach to determining false-positive rates resulting from resting fMRI connectivity analysis given that there are no naturally generated ‘connectivity free’ data in which spuriously high levels of connectivity could be detected. Perhaps there have been attempts with simulated data? This is not to say that we should continue to make classic assumptions in the case of resting fMRI functional connectivity analyses. But given that false positive rates vary as a function of block versus event-related approaches, it’s not clear, either, that the false-positive rates Eklund et al. report are due entirely to heavy tails in the spatial distribution of BOLD data that should, then, be assumed across all manner of fMRI analyses. Moving forward, we will make this assumption, however, until we have reason to do otherwise. Thoughts on this topic or, perhaps, alternative courses of action to recommend?
Many thanks!