Decrease of Deoxy-Hemoglobin Containing Blood Volume in Activated Human Visual Cortex

Xiang He¹, Dmitriy A. Yablonskiy¹

Quantification of brain hemodynamic parameters during functional activation is essential for understanding biophysical mechanisms behind blood oxygenation level depend (BOLD) phenomenon. Models of BOLD signal are often derived based on a relationship established by PET studies between cerebral blood volume (CBV) and cerebral blood flow (CBF), ignoring that only portion of CBV - deoxyhemoglobin-containing blood volume (DBV) affects BOLD signal. In this study, we directly measure DBV during visual activation in human visual cortex area using qBOLD-fMRI technique. We demonstrate for the first time that DBV decreases during functional activation an effect opposite to well known increase in CBV.