E, Enlarged anterior view of the right carotid bifurcation. The right M1 divides as a bifurcation before reaching the limen insula. Lenticulostriate arteries arise from the posterosuperior margin of the M1. The A1 also gives rise to perforating branches that enter the anterior perforated substance. F, Enlarged view of the lenticulostriate branches arising from the left M1 and entering the anterior perforated substance. The lateral end of the recurrent artery intermingles with the lenticulostriate branches of the M1 segment. The AChA is directed around the medial aspect of the uncus. G, Enlarged view of the left carotid bifurcation. Perforating branches arise from the PComA and ascend to enter the diencephalon medial to the optic tract. Lenticulostriate branches arise from the M1 and enter the anterior perforated substance. H, Anterior view of the lenticulostriate branches of M1 and a large recurrent artery in another specimen. The artery sends a small branch to the frontal lobe and might be called an accessory MCA. I, Anterior view. Some of the gray matter above the anterior perforated substance has been removed to expose the intraparenchymal course of the recurrent and lenticulostriate arteries. (Images courtesy of AL Rhoton, Jr.)