Effective connectivity or just plumbing? Granger Causality estimates highly reliable maps of venous drainage.

fMRI is not much better then EEG at determining what goes on in the living brain. Apart from the obvious such as: basic flaws in the theory, software errors, bad parameter setting, confirmation bias blocking of noisy parts, incompetence of the people using the device the system is also flawed because it is not even measuring what it claims to measure. Drop this hot potato fast and find another device.

Dr. Micah Allen

update: for an excellent response to this post, see the comment by Anil Seth at the bottom of this article. Also don’t miss the extended debate regarding the general validity of causal methods for fMRI at Russ Poldrack’s blog that followed this post. 

While the BOLD signal can be a useful measurement of brain function when used properly, the fact that it indexes blood flow rather than neural activity raises more than a few significant concerns. That is to say, when we make inferences on BOLD, we want to be sure the observed effects are causally downstream of actual neural activity, rather than the product of physiological noise such as fluctuations in breath or heart rate. This is a problem for all fMRI analyses, but is particularly tricky for resting state fMRI, where we are interested in signal fluctuations that fall in the same range as respiration and…

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