Xin Yu1, Stephen Dodd1, Yoshiyuki Hirano1, Daniel Glen2, Ziad S. Saad2, Richard C. Reynolds2, Afonso C. Silva1, Alan P. Koretsky1
BOLD-fMRI signals increase in the rat somatosensory cortex faster than the transit time of blood moving from arteries to veins, which enables us to measure the evolution of BOLD responses at early times after stimulation. Here, the rat barrel cortex activity was mapped at 0.2s temporal resolution in 2D GE-EPI images at 150mmx150μmx500μm using an 11.7T MRI. Activity-evoked BOLD signals were first observed at 0.8s, and shifted to adjacent penetrating venules at 1-1.2s, later propagating to the superficial draining veins. This indicates that BOLD-fMRI maps made prior to about 1 s will have minimal contribution from penetrating cortical venules.