01-10-2008, 01:33 PM
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Junior Member
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Join Date: Apr 2007
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how do i go about humanely testing rats for color-blindness?
for a school project
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01-10-2008, 01:35 PM
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Junior Member
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Join Date: Jul 2007
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Easy! I would train them for awhile by always putting the food in the same color box (have an empty box of a different color in the cage as well). When the rats have learned to consistently go to the color that the food is in, switch the food to the other colored box. If the rats have normal color vision they'll go for the wrong color first.
The only problem with this is that rats have a good sense of smell, which means that they'll be able to smell the food before they see it. So you'll need to have a fan nearbly blowing a good stream of air so that the box with food is always "downwind" of the rat.
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01-10-2008, 01:39 PM
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Junior Member
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Join Date: Jan 2008
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i don't know if you're in middle school, high school, or college. you can go to medical universities and ask for possible previous lab data or ask to participate in rat tests on vision. I've done mice experiment on the effects of glutamate on day and night vision or cones and rods. Basically contact the nearest Medical School for research opportunity, you can either participate or do an observation and request to have a copy of their data. Some places won't let you due to certain laws, it really depends on school and department policies. For me, i'm lucky to know a few doctors who perform these tests.
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01-10-2008, 01:53 PM
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Junior Member
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Join Date: Jan 2008
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give stewart little a call and ask him!!
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01-10-2008, 01:54 PM
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Junior Member
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Join Date: Jan 2008
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Color vision
Human and rat retinas have two types of light receptors: cones are sensitive to bright light and color, and rods are sensitive to dim light and cannot see color. Human and rat retinas differ, however, in the types and density of cones in the retina, which has implications for color vision.
Color vision in the retina: Humans have three types of color cones in our retinas. We have "trichromatic" vision, consisting of short-wavelength "blue" cones, middle-wavelength "green" cones and long-wavelength "red" cones.
Rats have just two types of cones (called "dichromatic" vision): a short "blue-UV" and the middle "green" cones (Szel 1992). The "green" cones' peak sensitivity is around 510 nm (Radlwimmer 1998), but the "blue" cones are shifted toward even shorter wavelengths than human blue cones, peaking at 359 nm. This means rats can see into the ultraviolet, they can see colors we can't see (Jacobs et al. 1991; 2001).
About 88% of a rat's cones are the middle "green" type, and 12% are the long blue-UV cones (Jacobs et al. 2001), the blue-UV cones are located in a zone at the bottom of the retina (Szel et al. 1996). For more on how ultraviolet and red-green color vision evolved, see Shi et al. 2001; Yokoyama and Radlwimmer 1999, 2001; Shi and Yokoyama 2003.
Color perception: So, the rat's retina is sensitive to greens and to blue-ultraviolet. Can the rat actually perceive different colors, and distinguish between them? For a long time, rats were throught to be completely colorblind (e.g. Crawford et al. 1990). Recent behavioral experiments, however have shown that rats can indeed perceive ultraviolet light, and with training can distinguish between ultraviolet and visible light, and between different colors in the blue-green range (Jacobs et al. 2001).
What would such vision look like? Animals with red-green colorblindness would be able to distinguish blues from greens, but reds would appear dark to them. They would also have a "neutral" point in the blue-green area of the spectrum: they cannot distinguish these blue-green hues from certain shades of gray. The rat's color vision merges into the ultraviolet, however, so they can see ultraviolet shades that we cannot (see flowers under ultraviolet light to get an idea of what UV looks like).
Rats don't have many cones, though -- 99% of the rat retina consists of rods, which sense only light and dark, and only 1% consists of cones (LaVail 1976), compared to a human's 5% (Hecht 1987). So the rat's perception of color may be fainter than ours, and color cues may not be very important to rats. In fact, brightness appears to be far more important to rats than color. It is easy to train rats to behaviorally differentiate brightnesses, but difficult to train them to behaviorally differentiate colors (Jacobs et al. 2001).
So, while rats are physically capable of distinguishing between ultraviolets, blues, and greens, such differences may not be very meaningful to them. This gets into the whole "just noticeable difference" vs. "just meaningful difference" concept, first introduced by Nelson and Marler (1990).
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01-10-2008, 01:54 PM
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Junior Member
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Join Date: Jan 2008
Posts: 2
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Color vision
Human and rat retinas have two types of light receptors: cones are sensitive to bright light and color, and rods are sensitive to dim light and cannot see color. Human and rat retinas differ, however, in the types and density of cones in the retina, which has implications for color vision.
Color vision in the retina: Humans have three types of color cones in our retinas. We have "trichromatic" vision, consisting of short-wavelength "blue" cones, middle-wavelength "green" cones and long-wavelength "red" cones.
Rats have just two types of cones (called "dichromatic" vision): a short "blue-UV" and the middle "green" cones (Szel 1992). The "green" cones' peak sensitivity is around 510 nm (Radlwimmer 1998), but the "blue" cones are shifted toward even shorter wavelengths than human blue cones, peaking at 359 nm. This means rats can see into the ultraviolet, they can see colors we can't see (Jacobs et al. 1991; 2001).
About 88% of a rat's cones are the middle "green" type, and 12% are the long blue-UV cones (Jacobs et al. 2001), the blue-UV cones are located in a zone at the bottom of the retina (Szel et al. 1996). For more on how ultraviolet and red-green color vision evolved, see Shi et al. 2001; Yokoyama and Radlwimmer 1999, 2001; Shi and Yokoyama 2003.
Color perception: So, the rat's retina is sensitive to greens and to blue-ultraviolet. Can the rat actually perceive different colors, and distinguish between them? For a long time, rats were throught to be completely colorblind (e.g. Crawford et al. 1990). Recent behavioral experiments, however have shown that rats can indeed perceive ultraviolet light, and with training can distinguish between ultraviolet and visible light, and between different colors in the blue-green range (Jacobs et al. 2001).
What would such vision look like? Animals with red-green colorblindness would be able to distinguish blues from greens, but reds would appear dark to them. They would also have a "neutral" point in the blue-green area of the spectrum: they cannot distinguish these blue-green hues from certain shades of gray. The rat's color vision merges into the ultraviolet, however, so they can see ultraviolet shades that we cannot (see flowers under ultraviolet light to get an idea of what UV looks like).
Rats don't have many cones, though -- 99% of the rat retina consists of rods, which sense only light and dark, and only 1% consists of cones (LaVail 1976), compared to a human's 5% (Hecht 1987). So the rat's perception of color may be fainter than ours, and color cues may not be very important to rats. In fact, brightness appears to be far more important to rats than color. It is easy to train rats to behaviorally differentiate brightnesses, but difficult to train them to behaviorally differentiate colors (Jacobs et al. 2001).
So, while rats are physically capable of distinguishing between ultraviolets, blues, and greens, such differences may not be very meaningful to them. This gets into the whole "just noticeable difference" vs. "just meaningful difference" concept, first introduced by Nelson and Marler (1990).
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02-05-2008, 11:02 PM
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Join Date: Feb 2008
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supelaahrma here
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02-06-2008, 02:08 PM
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Join Date: Feb 2008
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