Pial collaterals propagate neurovascular responses across functional units

Neurovascular coupling refers to the regulation of cerebral blood flow in response to neuronal activity, a process forming the basis for multiple functional neuroimaging techniques. However, the mechanisms that coordinate neurovascular responses across distinct cortical arterial territories remain poorly understood. Here we show that pial collaterals, arterio-arterial connections traditionally considered dormant under physiological conditions, serve as active conduits that propagate neurovascular signals between adjacent cortical territories and functional units. We demonstrate that neuronal activity in the somatosensory cortex triggers direct vascular signaling via endothelial Kir2.1 channels through pial collaterals, synchronizing blood flow responses beyond the activated area. The loss of pial collaterals abolished inter-territorial coupling without affecting local neurovascular responses. These results reveal that pial collaterals are critical regulators of cerebral perfusion.