Direct Imaging of Microvascular & Macrovasular Contributions by Time Resolved BOLD fMRI Allows Better Separation of Whisker Rows in the Rodent Barrel Cortex

Xin Yu¹, Stephen Dodd¹, Afonso Silva¹, Alan Koretsky¹

High spatial resolution EPI images could visualize the intracortical vasculature and allow separation of voxels containing large intracortical veins from surrounding voxels enriched with microvasculature. Early positive BOLD response at 0.8 s following stimulus onset mainly encompassed voxels containing the microvasculature. By 1.6 s activation was more prominent in veins even at cortical layer 4. Functional maps of whisker-row specific barrel areas were clearly separated at 0.8s, but were overlapped by large vessels at later times. These results demonstrate that early positive BOLD fMRI response has better spatial specificity to active regions due to exclusion of contributions from cortical veins.