Abstract
Abstract: :
Purpose: To study the neuronal basis of the red–green dimension of colour vision. Methods: We compared the responses of parvocellular–pathway cells in dichromatic ("red–green colour–blind") and trichromatic individuals of a species of New World monkey, the marmoset (Callithrix jacchus). Extracellular single–cell recordings were made in the parvocellular (PC) layers of the lateral geniculate nucleus of Sufentanil–anaesthetised marmosets. Visual stimuli included coloured and achromatic gratings, and spatially uniform superimposed red and green lights presented at varying temporal phases and frequencies. The colour vision genotype of each animal was established by polymerase chain reaction amplification of cone opsin–encoding genes. Results: The red–green chromatic sensitivity of parvocellular cells in trichromatic marmosets was proportional to the spectral separation between the medium– and long–wavelength sensitive cone pigments (20 nm or 7 nm). The temporal frequency–dependence of chromatic sensitivity was consistent with centre–surround interactions. The receptive field dimensions of parvocellular cells were similar in dichromatic and trichromatic animals. Conclusions: Red–green opponency may be a simple consequence of the retinal circuitry which gives rise to spatial (centre–surround) interactions, in combination with the expression of three cone pigment types in the same retina.
Keywords: color pigments and opsins • thalamus/lateral geniculate nucleus • color vision