Gunnar Svaetichin was a Swedish-Finnish-Venezuelan

Venezuelan people

Venezuelan people are from a multiethnic nation in South America called Venezuela. Venezuelans are predominantly Roman Catholic and speak Spanish, and a majority of them are the result of a mixture of Europeans, Africans, and Amerindians.-Demography:...

 physiologist

Physiology

Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 who, in 1956, showed by examining the external layers of fish retina

Retina

The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

s that electroretinograms

Electroretinography

Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors , inner retinal cells , and the ganglion cells. Electrodes are usually placed on the cornea and the skin near the eye, although it is possible to record the ERG from skin electrodes...

 display particular sensitivity to three different groups of wavelength

Wavelength

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

s in the areas of blue, green and red. This provided the first biological demonstration in support of the Young-Helmholz trichromatic theory. He also gave name to the S-potential, which was the first experimental evidence that opponency existed in the visual system

Vision

Vision or visions may refer to:* Visual perception, interpreting what is seen* Visual system, the sensory mechanism of eyesight* Vision , inspirational experiences* Hallucination, vivid conscious perception in the absence of a stimulus...

.

Additional reading

Jameson D., Hurvich L.M. (1982). Gunnar Svaetichin: man of vision. Prog Clin Biol Res., 13, 307-10.

http://www.hubel.med.harvard.edu/book/ch8.pdf

http://www.adsabs.harvard.edu/abs/1984Natur.308..360H

http://www.nature.com/nature/journal/v308/n5957/abs/308360a0.html

http://www.americanscientist.org/issues/id.841,y.2003,no.1,content.true,page.1,css.print/issue.aspx

Book prepared posthumously in Gunnar Svaetichin's honor.