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Sleep resets color vision, tests suggest

Color perception drifts from neutrality during wakefulness and is restored during sleep, according to research to be presented today in San Antonio, Texas, at SLEEP 2010, the 24th annual meeting of the Associated Professional Sleep Societies.

A joint venture of the American Academy of Sleep Medicine (AASM) and the Sleep Research Society, the annual SLEEP meeting brings together 5,000 clinicians and scientists in the fields of sleep medicine and sleep research.

According to AASM, scientists had not previously investigated how sleep might affect the way we view the world around us.

“Results indicate that prior wakefulness caused the color gray to be classified as having a slightly but significantly greenish tint. Overnight sleep restored perception to achromatic equilibrium so that gray was perceived as gray,” AASM said in a news statement.

“This is among the first studies to investigate the effects of sleep on perception,” said principal investigator and lead author Bhavin Sheth, assistant professor of electrical and computer engineering at the University of Houston in Texas. “Our findings suggest that wakefulness causes color classification to drift away from neutrality, and sleep restores color classification to neutral.”

Secrets of Sleep Quiz (National Geographic Magazine)

The study involved five people who viewed a full-field, homogenous stimulus of either slightly reddish or greenish hue. The observers had to judge whether the stimulus was greener or redder than their internal perception of neutral gray. “Across trials the hue was varied. One pair of monocular tests was performed just before participants went to sleep, and testing was repeated after participants slept for an average of 7.7 hours,” AASM said.

“Further testing found that overnight, full-field monocular stimulation with a flickering red ‘ganzfeld’ failed to nullify the resetting, sleep-induced effect. An achromatic stimulus was still less likely to be classified as greenish following sleep, with no statistical difference in the magnitude of the resetting in each eye.”

According to the authors, this suggests that color resetting is an internal process that is largely unaffected by external monochromatic visual stimulation.

The research is among more than 1,100 presentations at SLEEP 2010 that will showcase new findings that contribute to the understanding of sleep and the effective diagnosis and treatment of sleep disorders such as insomnia, narcolepsy and sleep apnea.