The astrocyte end-feet that are encircling the endothelial cells were thought to aid in the blood-brain barrier maintenance, but recent research shows that they do not involve in a substantial role; instead, it is the basal lamina and tight junctions of the cerebral endothelial cells that play a substantial role in maintaining the barrier. However, it has recently been shown that astrocyte activity is linked to the brain's blood flow and that this is actually being measured in fMRI.