Can current fMRI techniques reveal the micro-architecture of cortex?

In a recent paper in Nature Neuroscience, Kim et al.1 claimed to have visualized orientation columns in the visual cortex of cats by means of high-field, spatially resolved functional magnetic resonance imaging (fMRI). This would represent a striking technical advance indeed, if their mapping method were robust to noise and if the recorded patterns were reproducible within a given experimental session. A careful examination of their data, however, suggests that this may not be the case. Because the maps obtained in this study rely on a specific phase of the hemodynamic response, I will begin by briefly reviewing a few basic principles