Topographic map. Cortical Magnification



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Spatial Organization in the Cortex

Recall the Cortical Map of the Visual Field (From Wolfe, Kluender, & Levi)






Mapping.
There is a mapping of the retina to the cortex.
It’s sometimes called a retinotopic map.
Sometimes it’s called a topographic map.
Cortical Magnification
Although the figure here does not illustrate that magnification,

Area 5 in the cortex is much larger than Area 9 or Area 1.



5

5
Many more brain neurons are used for processing a given area of the fovea (area 5 in the retina) than are used for the same area of the periphery of the retina (areas 9/1 in the retina)
So the “pictures” shown in the cortex in this figure should be distorted, with huge amounts of space given to Area 5 and much smaller shown being given to Area 9/1.


Columns of neurons in V1 G9 p. 80
Neurons in V1 are organized in columns – 6 neurons per column, since there are 6 layers of neurons in the cortex.
Neurons within each column respond to similar aspects of the visual stimulus
Each different column represents a different location in the visual field – All neurons within the same column all respond the same location in the visual field.


Surface of cortex



Three randomly selected columns from V1.


Neurons within each column have the same receptive field.



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