Direct Imaging of Distinct Vascular Elements Detected by BOLD and Iron Oxide Based Blood Volume Using High Resolution FMRI of the Rodent Whisker Barrel

Xin Yu¹, Benjamin Porter¹, Stephen Dodd¹, Afonso Silva¹, Alan Koretsky¹

Direct characterization of the intracortical changes in vascular elements eliciting BOLD and CBV remains challenging. We measured BOLD and iron oxide based CBV in layer IV/V of the barrel cortex after whisker pad stimulation at high temporal (100msec) and spatial resolutions (150 x150m) using EPI and fast gradient-echo MRI. Low intensity EPI voxels corresponded to activated BOLD voxels and were attributed to venules. Voxels activated using BOLD were non-overlapping with CBV voxels. Fast activations (<500msec) and distinct locations from BOLD voxels led us to attribute these CBV voxels primarily to penetrating arterioles known to vasodilate during increased neural activity.