Cortically Magnified

Fourier analysis says that complex patterns can be created by adding up a large number of patterns as simple as sinusoidal waves. To make the idea more concrete, I like to use the following analogy in teaching: Imagine that you lived in the early 19th century. If you wanted to listen to a symphony, the only way to make it happen was to hire a few dozen highly-trained musicians to perform it for you.

The visuotopic map of the marmoset dorsomedial visual cortex (area DM; see references) is sufficiently complex that it is probably worthwhile to design a few visual aides to make it more intuitive. The figure above is my first attempt. In this figure, DM is divided into three segments, with the most medial segment representing central upper visual field (nose and eye of Sir Isaac Newton), the middle segment representing the entire lower visual field, and the medial segment representing the peripheral upper visual field (the forehead and hair of Newton).

I created this figure to illustrate the retinotopic map of the primary visual cortex of the marmoset. The eccentricity contours are plotted in red, and polar angles are in blue. It’s very easy to create it in 3D so that you can rotate it around and see it from different angles. This is how you do it: Download ParaView, the open source 3D data visualization package.