Physiological Issues Related to Color in Dreams

To sleep: perchance to dream

In the past, sleep has been considered an analogue of death during which there is no brain function. Currently sleep is more accurately characterized as an analogue of wakefulness involving a special form of mental activity. Such activity may be expressed in dreams, and whereas some dream experiences parallel common waking activities, others may be surreal or beyond the physical and other capabilities of the roused dreamer. Dreams may range from being vague, imageless and colorless to vivid and accompanied by sensations closely resembling normal conscious experience.

Vivid dreaming occurs primarily during rapid eye movement (REM) sleep, a period during which the eyes undergo bursts of jerky movements. Most individuals recall their dreams when awakened from this stage of sleep. Mental activity also occurs during slow-wave sleep, a stage of deep sleep occurring before REM sleep. Individuals are not easily roused from this stage and few recall dreams when awakened from slow-wave sleep.

Color and the human eye

As early as the seventeenth to the nineteenth centuries, scientists such as Sir Isaac Newton, Thomas Young, Hermann von Helmholtz and Ewald Hering contributed research that helped in the understanding of the mechanisms of color vision involving the human eye. Vision in humans is stimulated by the very narrow visible region of the electromagnetic spectrum that spans wavelengths from violet light at 400 nm to red light at 700 nm. Color vision is made possible when light of certain wavelengths from the sun or other sources impinge on three color-responding, receptors in the retina. These receptors are responsible for the so-called tri-chromacy of vision. Each receptor contains only one of three pigments. The pigment denoted S for short or B for blue, is sensitive to short wavelengths and is strongly responsible for the perception of the color blue; the M or G pigment is responsive to middle wavelengths and contributes to the perception of green; and the L or R pigment responds to longer wavelengths and makes a strong contribution to the perception of the color red. James Clerk Maxwell’s color-matching experiments showed that all spectral colors could be matched with some mixtures of three primary colors chosen from the red, green and blue regions of the spectrum.^{6, 7} The perception of color is based on three different factors, namely, hue, saturation and lightness. Hue is what is ordinarily meant by color, for example, red in distinction to yellow, whereas saturation indicates richness of hue. Lightness indicates the level of illumination. A color with zero percent lightness appears black (no light) whereas one with 100 percent lightness is fully illuminated so that the color is washed out and appears white.

Color and the human brain

Newton noted that although seemingly tangible, color is simply an illusion that rises in the mind. It is a sensation triggered by the complex exchange between light and object, mind and brain. He asserted that there is no color in the physical world; instead, the sensation of color is created inside us.⁸ Strong evidence of the involvement of the human brain in color vision, and by extension, color in dreams, has come from the careful documentation of the responses of neurology patients.

As early as1884 Hermann Wildebrand suggested that there must be separate visual centers in the primaryvisual cortex for ‘light impressions’, ‘form impressions’ and ‘color impressions’. His assertion that there was a separate ‘colorimpression’ site was later supported when Louis Verrey reported a patient who lost color vision as a result of a stroke which affected the left hemisphere of her brain. There are other early reports of patients who have suffered cerebral achromatopsia, or color blindness as a result of brain damage. One patient suffered a stroke that left him with normal visual acuity and normal visual fields but with severely impaired color vision. At autopsy, the lesion was found in the rear portion of the visual cortex. We now know that the segregation of color information from information about form and movement starts in the retina and is further processed by systems within the visual cortex. ⁷

In his book ‘An Anthropologist on Mars’ ⁹ noted neurologist Oliver Sacks who recently gave the inaugural lecture of the “Science in your Life” semester at Emory, gave an account of ‘The Case of the Colorblind Painter’. The patient was a self-described ‘rather successful artist’ who lost his color vision after a car accident. To him, everything now appeared as if on a black and white television screen, people looked like animated grey statues, and food looked dead and disgusting. Interestingly, the artist said that before he lost his color vision he had often dreamed in vivid color but now he described his dreams as “washed out and pale, or violent and contrasty, lacking both color and delicate tonal gradations.” Sacks notes that the suddenness of the loss of color vision is not consistent with slow deterioration of cone cells in the retina, but rather a mishap in those parts of the brain that specialize in color perception.

In his work The Interpretation of Dreams,¹⁰ Sigmund Freud cited the suggestion by Max Wilhelm Wundt that objective (external) sensory excitations during sleep play a part in provoking dreams. An essential part is also played by the subjective (internal) visual and auditory sensations that are familiar to us in the waking state, in producing the illusions that occur in dreams. The internal excitations of the retina are considered to be especially important. There is clearly a correlation between the mechanisms of color perception that operate during wakefulness and those that operate during dreaming. The idea of a color center in the brain can account for the fact that even though the sensory organs largely responsible for color perception during wakefulness are not subject to the same stimuli during sleep, the same effect is reproduced in dreams. Clearly, color perception is a result of the cooperation of both visual and neural processing and it is reasonable that this same kind of neural processing, largely aided by memory, is responsible for color in dreams.


	click here for author biography Physiological Issues Related to Color in Dreams To sleep: perchance to dream In the past, sleep has been considered an analogue of death during which there is no brain function. Currently sleep is more accurately characterized as an analogue of wakefulness involving a special form of mental activity. Such activity may be expressed in dreams, and whereas some dream experiences parallel common waking activities, others may be surreal or beyond the physical and other capabilities of the roused dreamer. Dreams may range from being vague, imageless and colorless to vivid and accompanied by sensations closely resembling normal conscious experience. Vivid dreaming occurs primarily during rapid eye movement (REM) sleep, a period during which the eyes undergo bursts of jerky movements. Most individuals recall their dreams when awakened from this stage of sleep. Mental activity also occurs during slow-wave sleep, a stage of deep sleep occurring before REM sleep. Individuals are not easily roused from this stage and few recall dreams when awakened from slow-wave sleep. Color and the human eye As early as the seventeenth to the nineteenth centuries, scientists such as Sir Isaac Newton, Thomas Young, Hermann von Helmholtz and Ewald Hering contributed research that helped in the understanding of the mechanisms of color vision involving the human eye. Vision in humans is stimulated by the very narrow visible region of the electromagnetic spectrum that spans wavelengths from violet light at 400 nm to red light at 700 nm. Color vision is made possible when light of certain wavelengths from the sun or other sources impinge on three color-responding, receptors in the retina. These receptors are responsible for the so-called tri-chromacy of vision. Each receptor contains only one of three pigments. The pigment denoted S for short or B for blue, is sensitive to short wavelengths and is strongly responsible for the perception of the color blue; the M or G pigment is responsive to middle wavelengths and contributes to the perception of green; and the L or R pigment responds to longer wavelengths and makes a strong contribution to the perception of the color red. James Clerk Maxwell’s color-matching experiments showed that all spectral colors could be matched with some mixtures of three primary colors chosen from the red, green and blue regions of the spectrum.^{6, 7} The perception of color is based on three different factors, namely, hue, saturation and lightness. Hue is what is ordinarily meant by color, for example, red in distinction to yellow, whereas saturation indicates richness of hue. Lightness indicates the level of illumination. A color with zero percent lightness appears black (no light) whereas one with 100 percent lightness is fully illuminated so that the color is washed out and appears white. Color and the human brain Newton noted that although seemingly tangible, color is simply an illusion that rises in the mind. It is a sensation triggered by the complex exchange between light and object, mind and brain. He asserted that there is no color in the physical world; instead, the sensation of color is created inside us.⁸ Strong evidence of the involvement of the human brain in color vision, and by extension, color in dreams, has come from the careful documentation of the responses of neurology patients. As early as1884 Hermann Wildebrand suggested that there must be separate visual centers in the primaryvisual cortex for ‘light impressions’, ‘form impressions’ and ‘color impressions’. His assertion that there was a separate ‘colorimpression’ site was later supported when Louis Verrey reported a patient who lost color vision as a result of a stroke which affected the left hemisphere of her brain. There are other early reports of patients who have suffered cerebral achromatopsia, or color blindness as a result of brain damage. One patient suffered a stroke that left him with normal visual acuity and normal visual fields but with severely impaired color vision. At autopsy, the lesion was found in the rear portion of the visual cortex. We now know that the segregation of color information from information about form and movement starts in the retina and is further processed by systems within the visual cortex. ⁷ In his book ‘An Anthropologist on Mars’ ⁹ noted neurologist Oliver Sacks who recently gave the inaugural lecture of the “Science in your Life” semester at Emory, gave an account of ‘The Case of the Colorblind Painter’. The patient was a self-described ‘rather successful artist’ who lost his color vision after a car accident. To him, everything now appeared as if on a black and white television screen, people looked like animated grey statues, and food looked dead and disgusting. Interestingly, the artist said that before he lost his color vision he had often dreamed in vivid color but now he described his dreams as “washed out and pale, or violent and contrasty, lacking both color and delicate tonal gradations.” Sacks notes that the suddenness of the loss of color vision is not consistent with slow deterioration of cone cells in the retina, but rather a mishap in those parts of the brain that specialize in color perception. In his work The Interpretation of Dreams,¹⁰ Sigmund Freud cited the suggestion by Max Wilhelm Wundt that objective (external) sensory excitations during sleep play a part in provoking dreams. An essential part is also played by the subjective (internal) visual and auditory sensations that are familiar to us in the waking state, in producing the illusions that occur in dreams. The internal excitations of the retina are considered to be especially important. There is clearly a correlation between the mechanisms of color perception that operate during wakefulness and those that operate during dreaming. The idea of a color center in the brain can account for the fact that even though the sensory organs largely responsible for color perception during wakefulness are not subject to the same stimuli during sleep, the same effect is reproduced in dreams. Clearly, color perception is a result of the cooperation of both visual and neural processing and it is reasonable that this same kind of neural processing, largely aided by memory, is responsible for color in dreams.