Cuneus

The cuneus, also known as the cuneate gyrus, is a wedge-shaped area in the back part of the brain called the occipital lobe. You can see it on the inner surface of the occipital lobe, where it is surrounded by the parietooccipital sulcus in the front and the calcarine sulcus below and behind it.

To understand the role of the cuneus in visual processing, it is important to know that within the occipital cortex, the calcarine sulcus divides the cuneus (or cuneate gyrus) above it from the gyrus below it, which is called the lingula (or lingual gyrus). The primary visual area, known as Broadman's area 17, is found on both sides of the calcarine sulcus, spreading across the cuneus and the lingula. The cuneus forms the upper lip of the calcarine sulcus, while the lingula forms the lower lip.

It is important to note that visual information from the lower part of the visual field, which is projected onto the upper part of the retina, is received by the cuneus through the superior optic radiations in the primary visual area within the upper lip of the calcarine sulcus. Furthermore, the right visual field is processed by the left occipital cortex, while the left visual field is processed by the right occipital cortex. In essence, the visual field can be divided into four quadrants. In the case of the cuneus on the left side, it receives visual information from the lower quadrants of the right visual field. If there is damage to this area, it can result in a condition called right inferior homonymous quadrantanopia (with or without macular sparing).