Brief visual stimulation allows mapping of ocular dominance in visual cortex using fMRI

We have used high spatial resolution (0.55 mm x 0.55 mm) functional magneti c resonance imaging (fMRI) to show that when stimulus duration is brief (<6 sec), the hyperoxic hemodynamic response to neural activity can resolve th e columnar architecture of ocular dominance within the primary visual corte x of humans. Our fMRI maps of ocular dominance columns are strikingly simil ar in appearance, size, and orientation to those reported in the literature using optical imaging of intrinsic signals (OIS) in animal cortex and hist ology of post-mortem human specimens. We also demonstrate that under brief visual stimulation conditions, our results are consistent over repeated exp eriments. This is not the case for long duration stimuli (greater than or e qual to 10 sec). A simulated random data set exhibited the same response pr operties as maps obtained when using these prolonged visual stimuli. Our re sults suggest that brief visual stimulation is essential for fMRI to succes sfully resolve ocular dominance columns using the hyperoxic phase of the he modynamic response to neural activity at our prescribed spatial resolution. (C) 2001 Wiley-Liss, Inc.