The LGN and Visual Cortex

The major input to the visual cortex is from the lateral geniculate nucleus (LGN). The LGN is composed of six layers. The bottom two shown in light blue are the magnocellular layers. These layers are concerned primarily with non color vision processing. The top four layers shown in dark blue are the parvocellular layers and are very important for color vision.

Three of the layers receive input from the ipsilateral eye and the other three form the contralateral eye. (ipsi means same side, contra means opposite side).

In the LGN- cortical diagram you can see the connections between the different LGN layers and the visual cortex. Note that some layers go to the right eye and the others go to the left. Also you can see in which layers of the cortex that the different LGN layer terminate.

The solid rectangle is a portion of cubical section that is usually shown as the cortical cube model. This solid rectangle shows the notable features. Ocular dominance is shown as the red and green areas. The green area represents the right eye and the red area the left. On the right side of the rectangle you can see the columns and their respective orientation specificities. The yellow areas are called the blobs. The blobs are visually identified with a light microscope after the cortex is treated with a substance to enhance the cytochrome oxidaze of the cells. These blob areas are important for color vision processing.

The numbers on the left side of the rectangle identify the layers of the cortex.

LGN- cortical diagram

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