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Magn Reson Med. 1999 Feb;41(2):230-5.

Submillimeter functional localization in human striate cortex using BOLD contrast at 4 Tesla: implications for the vascular point-spread function.

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  • 1Department of Medical Biophysics, The University of Western Ontario, London, Canada.


Using multislice segmented echoplanar imaging at 4 T, we have measured an upper bound to the cortical vasculature point-spread function (PSF) using functional magnetic resonance imaging (fMRI) in humans. Our experiments demonstrate that cortical subunits that are approximately 700 microm apart can be resolved using the early part of the hyperoxygenation phase of the blood oxygenation level-dependent (BOLD) effect. This was accomplished using brief (4 sec) single trials of monocular and binocular stimulation of ocular dominance columns in human primary visual cortex. The data suggest that at even higher magnetic fields, the cortical vasculature PSF may be limited by the extent and nature of horizontal connections and not signal-to-noise ratio.

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