The observed α-SMA-mediated contractility in response to ischemic injury and the role of calcium in the regulation of the contractile response, refine and expand our understanding of the pericytes in relation to blood flow at the single-capillary level in health as well as neurodegenerative conditions including retinal ischemia, diabetic retinopathy, stroke and Alzheimer’s disease. The gene discussed is ACTA1; the disease is Alzheimer disease.