Layers four and six (4 & 6) of the LGN also connect to the opposite eye, but to the P cells (color and edges) of the optic nerve. By contrast, layers two, three and five (2, 3, & 5) of the LGN connect to the M cells and P (parvocellular) cells of the optic nerve for the same side of the brain as its respective LGN.
A gyrus (gyri pl) is a rounded ridge, as on the surfaces of the cerebral hemispheres. A sulcus is a groove in the surface between gyri.
Gray's Fig. 727 - Medial surface of left cerebral hemisphere. In neuroanatomy, a sulcus (Latin: furrow, pl. sulci) is a depression or groove in the cerebral cortex. It surrounds a gyrus (pl. gyri), creating the characteristic folded appearance of the brain in humans and other mammals. 1 Structure.