Cortically Magnified

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.

PNAS recently published a cognitive anthropology paper titled Mangarevan invention of binary steps for easier calculation. The paper describes an arithmetic system that had been used for hundreds of years by islanders living in Mangareva (a small island in French Polynesia) for the purpose of “counting a small group of highly valued objects such as turtles, fish, coconuts, octopuses, and breadfruits”. This system is not too different from the decimal system that we’re using today, except that a number in the Mangarevan language can contain a small segment of binary code, which employs four numerals to represent 10 multiplied by the first four powers of 2.

This figure illustrates the direction tuning curves of two motion sensitive neurons recorded in the primary visual cortex. The two neurons were so close to each other that their activities could be picked up by the same electrode. Interestingly they preferred polar opposite directions.

Demonstrations: The reconstruction of Mona Lisa video. A blog post I wrote about the Fourier transform trick. Youtube video: Nobel laureates David Hubel and Torsten Wiesel recording neurons in cat’s V1. Suggested readings: Fourier transform An introduction to two-dimensional fast Fourier transforms and their applications by Rzeszotarski et al. (1983). Fourier transforms and frequency-domain processing (Chapter 5 of Fundamentals of Digital Image Processing: A Practical Approach with Examples in Matlab by Solomon & Breckon, 2011) Suggested readings: programming See this web page from UCSB.