Abstract #0508

From Two-Photon Microscopy to BOLD-FMRI: Association of an Undershoot of Arteriolar Diameter with the BOLD Post-Stimulus Undershoot

Anna Devor^1,2, Richard Buxton³, Peifang Tian¹, Ivan Teng¹, Kun Lu¹, Larry May¹, Ron Kurz¹, Anders Dale¹

¹University of California, San Diego; ²Martinos Center for Biomedical Imaging, Harvard; ³University of California, San Diego, La Jolla, CA, USA

Although the origins of the BOLD post-stimulus undershoot have been debated since the early days of fMRI, there is still no consensus on whether it is a neural, metabolic or vascular effect, and experimental evidence has been presented for each interpretation. To test directly whether vascular dynamics are evident during the post-stimulus undershoot, we performed BOLD-fMRI and 2-photon microscopic dynamic vascular diameter measurements under the same conditions in rat primary somatosensory cortex (SI). Although there was no evidence of a venous balloon effect, arteriolar diameter exhibited a post-stimulus undershoot with a similar time scale to the BOLD post-stimulus undershoot, suggesting a vascular rather than metabolic origin for the undershoot.