  It is a principal open question whether noninvasive imaging methods in humans
can decode information encoded at a spatial scale as fine as the basic
functional unit of cortex: cortical columns. We addressed this question in five
magnetoencephalography (MEG) experiments by investigating the encoding of a
columnar-level encoded visual feature: contrast edge orientation. We found that
MEG signals contained orientation-specific information as early as ~50ms after
stimulus onset even when controlling for confounds, such as overrepresentation
of particular orientations, stimulus edge interactions, and global form-related
signals. Theoretical modeling confirmed the plausibility of this empirical
result. An essential consequence of our results is that information encoded in
the human brain at the level of cortical columns should in general be
accessible by multivariate analysis of electrophysiological signals.
