An Assessment of the Post-Stimulus Undershoot Using Hyperoxic BOLD Contrast and ASL

Ian D. Driver¹, Emma L. Hall¹, Paula L. Croal¹, Susan T. Francis¹, Penny A. Gowland¹

The BOLD post-stimulus undershoot (PSU) following a motor task is assessed at 7T through simultaneous measurement of BOLD, CBF, and venous CBV using hyperoxia. This work shows a post-stimulus undershoot in both the BOLD and CBF response, when the venous CBV response had returned to baseline. This suggests a neuronal origin for the PSU, but could also result from a delayed vascular compliance. Results show that at the spatial resolution (2 x 2 x 3 mm³), the PSU is not more localised to the underlying neuronal response, as reported in animal models.