Cellular Control of Brain Capillary Blood Flow: In Vivo Imaging Veritas

The precise modulation of regional cerebral blood flow during neural activation is important for matching local energetic demand and supply and clearing brain metabolites. Here we discuss advances facilitated by high-resolution optical in vivo imaging techniques that for the first time have provided direct visualization of capillary blood flow and its modulation by neural activity. We focus primarily on studies of microvascular flow, mural cell control of vessel diameter, and oxygen level-dependent changes in red blood cell deformability. We also suggest methodological standards for best practices when studying microvascular perfusion, partly motivated by recent controversies about the precise location within the microvascular tree where neurovascular coupling is initiated, and the role of mural cells in the control of vasomotility.