Most non primate mammals are known to possess
dichromatic color vision based on short-wavelength-sensitive
(S) and medium/long-wavelength-sensitive (ML) cone
photoreceptors. However, the neural pathways carrying
signals underlying the primitive “blue–yellow” axis of color
vision are largely unexplored in these animals. We have
recently characterized a population of color opponent blue-
ON cells in electrophysiological single-cell recordings from
the dorsal lateral geniculate nucleus (LGN) of anaesthetized
cats. We found remarkable similarities to previous
descriptions of primate blue-ON cells in terms of receptive
field size and structure and the relative weight of functional
inputs from the opponent cone classes. Moreover, cat blue-
ON cells were found in the same layers as W-cells, which are
thought to be homologous to the primate koniocellular
system. The temporal frequency optimum of cat blue-ON
cells was around 3 Hz, about one-third of that found in
achromatic cells. Based on these data, we suggest that cat
blue-ON cells are part of a "blue-yellow" color opponent
system that is the evolutionary homologue of the blue-ON
division of the koniocellular pathway in primates.
