a branch of the internal carotid artery that forms part of the circle of Willis. The anterior cerebral artery passes above the optic chiasm and extends forward into the longitudinal fissure, where it curves around the horn of the corpus callosum before arching back along the upper surface of the corpus callosum. It supplies blood to portions of the frontal lobe, which is involved in motor functions and higher level cognitive processes, and portions of the parietal lobe, which is involved in sensory functions. Specific structures served include the corpus callosum itself, the cingulate cortex, parts of the basal ganglia, and the septal area.