We performed doublecortin (a cell marker expressed by immature neurons emerging and migrating from the SVZ reflecting neurogenesis)33, 34 immunofluorescence on coronal brain sections generated 14-days post-stroke from young and aged animals that underwent photothrombosis and received either vehicle or PEG-IGF-I treatment starting 3 hrs, 1-day or 5-days post-stroke (Fig. 5A and B). Here, IGF1 is linked to Stroke.