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Principle Of Univariance
The principle of univariance is how one can discriminate between wavelengths through comparison of multiple photoreceptors. The principle states that one and the same visual receptor cell can be excited by different combinations of wavelength and intensity, so that the brain cannot know the color of a certain point of the retinal image. One individual photoreceptor type can therefore not differentiate between a change in wavelength and a change in intensity. Thus the wavelength information can be extracted only by comparing the responses across different types of receptors. The principle of univariance was first described by W. A. H. Rushton (p. 4P). Both cone monochromats (those who only have 1 cone type) and rod monochromats (those with no cones) suffer from the principle of univariance. The principle of univariance can be seen in situations where a stimulus can vary in two dimensions, but a cell's response can vary in one. For example, a colored light may vary in both wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoreceptor Cell
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. There are currently three known types of photoreceptor cells in mammalian eyes: rod cell, rods, cone cell, cones, and intrinsically photosensitive retinal ganglion cells. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form an image of the environment, Visual perception, sight. Rods primarily mediate scotopic vision (dim conditions) whereas cones primarily mediate photopic vision (bright conditions), but the processes in each that supports phototransduction is similar. The intrinsically photosen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monochromacy
Monochromacy (from Greek ''mono'', meaning "one" and ''chromo'', meaning "color") is the ability of organisms to perceive only light intensity without respect to spectral composition. Organisms with monochromacy lack color vision and can only see in shades of grey ranging from black to white. Organisms with monochromacy are called monochromats. Many mammals, such as cetaceans, the owl monkey and the Australian sea lion are monochromats. In humans, monochromacy is one among several other symptoms of severe inherited or acquired diseases, including achromatopsia or blue cone monochromacy, together affecting about 1 in 30,000 people. Humans Human vision relies on a duplex retina, comprising two types of photoreceptor cells. Rods are primarily responsible for dim-light scotopic vision and cones are primarily responsible for day-light photopic vision. For all known vertebrates, scotopic vision is monochromatic, since there is typically only one class of rod cell. However, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
