Gunnar Nils Toivo Svaetichin (13 January 1915 – 23 March 1981)[2] was a Swedish-Finnish-Venezuelan physiologist who, in 1956,[3] showed by examining the external layers of fish retinas that electroretinograms display particular sensitivity to three different groups of wavelengths in the areas of blue, green and red.

During his medical studies in Helsinki, Svaetichin got to know the young Ragnar Granit, who had returned after some years in the US and Oxford and become a professor of physiology.

[5] His first work as a doctor was when the Finnish Winter War broke out and Svaetichin was drafted and sent to a first aid station located just behind the front lines.

It was with this technique that Ragnar Granit could perform the studies of color vision, which subsequently earned him the Nobel Prize in 1967.

Over time these neurons came to be named horizontal cells, which have come to be foundational for our understanding of vision and for the development of the theory behind neural networks.