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October, 2006
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Color Vision: Function of the human eye that is used in bright illumination or in daylight (at photopic intensities). Photopic vision is performed by the three types of Retinal cone photoreceptors with varied peak absorption wavelengths in the color spectrum (from violet to red, 400 - 700 nm).

Color Afterimages

JoVE 10194

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Human color vision is impressive. People with normal color vision can tell apart millions of individual hues. Most amazingly, this ability is achieved with fairly simple hardware.

Part of the power of human color vision comes from a clever bit of engineering in the human brain. There, color perception relies on what is known as an 'opponent system.' This means that the presence of one kind of stimulus is treated as evidence for the absence of another, and vice versa; absence of one kind of stimulus is taken as evidence for the presence of the other. In particular, in the human brain there are cells that fire both when they receive signals to suggest that blue light is present, or when they do not receive signals suggesting yellow light. Similarly, there are cells that fire in the presence of yellow or the absence of blue. Blue and yellow are thus treated as opponent values in one dimension, and can be thought of as negative versus positive values on one axis of a Cartesian plane. If a stimulus is characterized as having a negative value on that axis, it can't also have a positive value. So, if it is characterized as yellow, it can't also be characterized as blue. Similarly, green and red (or really, magenta), o

 Sensation and Perception

Probing the Limits of Egg Recognition Using Egg Rejection Experiments Along Phenotypic Gradients

1Department of Biology, Long Island University-Post, 2Department of Animal Biology, School of Integrative Biology, University of Illinois, 3Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 4Department of Zoology and Laboratory of Ornithology, Palacký University, 5Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic

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JoVE 57512

 JoVE In-Press


JoVE 10280

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Human vision depends on light-sensitive neurons that are arranged in the back of the eye on a tissue called the retina. The neurons, called the rods and cones because of their shapes, are not uniformly distributed on the retina. Instead, there is a region in the center of the retina called the macula where cones are densely packed, and especially so in a central sub-region of the macula called the fovea. Outside the fovea there are virtually no cones, and rod density decreases considerably with greater distance from the fovea. Figure 1 schematizes this arrangement. This kind of arrangement is also replicated in the visual cortex: Many more cells represent stimulation at the fovea compared to the periphery. Figure 1. Schematic depiction of the human eye and the distribution of light-sensitive receptor cells on the retina. The pupil is the opening in the front of the eye that allows light to enter. Light is then focused onto the retina, a neural tissue in the back of the eye that is made of rods and cones, light-sensitive cells. At the center of the retina is the macula, and in

 Sensation and Perception

Key Elements of Photo Attraction Bioassay for Insect Studies or Monitoring Programs

1Arthropod-Borne Animal Diseases Research Unit, Center for Grain and Animal Health Research, Agricultural Research Service, United States Department of Agriculture, 2Center for Medical, Agricultural, and Veterinary Entomology, Agricultural Research Service, United States Department of Agriculture, 3Bayer

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JoVE 57445

 JoVE In-Press

Vibratome Sectioning Mouse Retina to Prepare Photoreceptor Cultures

1Department of Genetics, UMR_S 968, Institut de la Vision, 2Department of Visual Information, UMR_S 968, Institut de la Vision, 3Exploratory Team, UMR_S 968, Institut de la Vision, 4Sorbonne Universités, Paris 06, UMR_S 968, Institut de la Vision, 5INSERM, U968, Institut de la Vision, 6CNRS, UMR_7210, Institut de la Vision

JoVE 51954


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