View of the medial surface of the left hemisphere. Two retractors open and expose the parieto-occipital sulcus, showing the parieto-occipital artery originating from the P3 segment. 1, Parieto-occipital artery; 2, calcarine artery; 3, P3 segment; 4, P2P segment; 5, posterolateral choroidal artery; 6, lingula; 7, cuneus; 8, precuneus. (Image courtesy of E de Oliveira)