High-speed vascular dynamics of the hemodynamic response

►High frame rate optical imaging resolves rapid dynamics of cortical vasculature. ►Functional response begins in the parenchyma, before dilation of pial arterioles. ►Response proceeds with retrograde propagation of vasodilation in pial arterioles. ►Direction of propagation in arterioles is independent of direction of blood flow. ►Return to baseline may have different underlying mechanism compared to onset.