Which structure is the landmark that marks the boundary of the superior and inferior visual regions in the occipital lobe?

• A. Calcarine fissure
• B. Lunate sulcus
• C. Parieto-occipital fissure
• D. Preoccipital notch

Answer: (A)

The calcarine fissure on the medial surface of the occipital lobe is the key landmark for the primary visual cortex. The cortex that lies along the banks of this fissure houses V1, and its upper and lower banks correspond to opposite halves of the visual field, establishing the boundary between superior and inferior visual representations. In practical terms, the region above the fissure (the cuneus) and the region below it (the lingual gyrus) process different parts of the visual field, so this fissure marks where the division occurs. The lunate sulcus is not a reliable human landmark for this boundary, the parieto-occipital fissure separates occipital from parietal lobes rather than delineating visual-field halves, and the preoccipital notch is simply a skull landmark with no direct role in visual field mapping.