What does fMRI tell us about Neuronal Activity?

Heeger, D.J. & Ress, D. (February 2002). What does fMRI tell us about Neuronal Activity?, Nature Reviews, Volume 3, 142-151.

The linear transform model refers to a fundamental assumption guiding the analysis of fMRI studies, namely that fMRI signal is approximately proportional to a measure of local neural activity. Clearly, the ultimate success of this research depends on a clear relationship between the fMRI signal and the underlying neuronal activity. However, some scientists believe reasons exist to be skeptical of this pervasive assumption. Heeger and Ress provide a review of arguments on both sides, concluding that this model is a reasonable and useful approximation, but only for some recording sites, in some brain areas, and using certain experimental protocols.