Neurovascular coupling in the visual cortex

This research aimed to improve understanding of neurovascular coupling, focussing on the V1 area of the visual cortex. Neurovascular coupling is the process by which the energetic requirements of the brain are met by increases in local blood flow to areas of neuronal activity. The precise mechanisms underlying this are yet to be fully elucidated, however, it is likely to involve multiple cell types (including vascular mural cells, interneurons and astrocytes) through multiple possible pathways. Increasing our understanding of this process is of great importance: functional magnetic resonance imaging (fMRI) is a widely used technique that measures local changes in blood flow in order to extrapolate findings to neuronal activity. However, little is known about the relationship between increases in blood flow and the activity of specific neuronal subtypes underlying it. This therefore limits the conclusions that can be drawn and the level of detail in which it can be understood. Furthermore, a more nuanced understanding of the characteristics of the vasculature and how this relates to its functionality is required in order to deepen understanding of the role different vessel types and their accompanying vascular mural cells might play in neurovascular coupling, and more specifically how neuronal activity might differentially affect various parts of the vasculature with differing properties. Neurovascular coupling was probed using an in vivo mouse model with a chronic awake head fixed preparation, which allowed sporadic bouts of volitional locomotion. Through this method we were able to observe varying changes in vascular diameter and neuronal intracellular calcium with manipulation of a visual stimulus and varying patterns of locomotion. The function of the vasculature was also characterised in terms of vessel branching order, diameter and inter-soma distance of vascular mural cells; and using ex vivo immunolabellling, markers of vascular function were also characterised in relation to these characteristics.