Notes

The Striate Cortex presents a thick black line, which represents the layer 4 of V1, i.e., the layer where all the connections from LGN are received. In the dark picture: Cat V1 that has been labelled with radioactive label injected in one eye of the cat that has been transported all the way to V1. We can observe that there is an alternation between cells in L4 that receive from one eye and from the other, via the LGN. However, the vast majority of cells in V1 are binocular, even if in L4 the separation of ocular dominated cells is more evident.

You seem the same thing on the surface of L4 (monocular columns):

However, as soon as you get out of L4 (input layer), the cells are not monocular anymore, but rather binocular. Although receiving inputs from both eyes, most of these cells present ocular dominance, i.e., one eye induces an higher excitation of the cell. These cells are organized in ocular dominance columns.

These binocular property of V1 cells outside L4 is important to compare signals from both eyes, which in turns allows depth perception.

About half of the area of the cortex is dedicated to vision (because we are visual animals), however not all animals are visual animals, for example mice have more developed olfactory areas compared to visual ones. Some of these areas are only involved in visual perception and processing, while other are multi-sensory areas that combine signals from different sensory systems.

Each of these areas have a representation of the visual field, some a full one while others only a partial one. For example, V2 has a representation of the visual field which is almost retinotopic. These regions are organized in a hierarchy (right picture), which shows the connections between the areas. The connections between ganglionic cells and LGN are unidirectional, while the connections from LGN onwards are bidirectional (which have been distinguished in feedforward and feedback connections). V1 is strongly connected to V2 and V4, V2 is strongly connected to V4 and V3. The striate cortex of monkeys is very similar to the one of human. All the regions in the left of the hierarchy are part of the parietal lobe, while the right side is part of the temporal lobe. This two part represents respectively the What and Where Pathways.