Abstract #0899

Shen Q, Ren H, Duong T

Gradient-echo BOLD, CBF, CBV and CMRO2 fMRI signals were measured with 500-ms resolution associated with rat forepaw stimulation. Percent changes and onset times were analyzed for three cortical layers. BOLD change was largest in Layer I-III whereas CBF, CBV and CMRO2 changes were largest in Layer IV-V. Only BOLD time course from Layer I-III showed a post-stimulus undershoot. CBV increased first but was overtaken by CBF. BOLD significantly lagged both CBF and CBV. These results suggest that CBF change arises largely from arterioles, CBV change has some venous contribution during steady state, and BOLD signal is weighted by draining veins.