Human Nonvisual Responses to Simultaneous Presentation of Blue and Red Monochromatic Light

Feb 7, 2012Journal of biological rhythms

Human non-visual reactions to blue and red light shown at the same time

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Abstract

A significant irradiance response was observed with blue light (λ(max) 479 nm) for melatonin suppression.

Subjective alertness levels increased after light exposure, regardless of the wavelength or intensity of the light.
Plasma melatonin levels were significantly suppressed by blue light exposure.
Co-administration of red light (λ(max) 627 nm) did not significantly change the melatonin suppression caused by blue light.
The intensity of blue light was identified as the primary factor affecting melatonin suppression.
The study involved 21 young healthy men in controlled laboratory sessions with various light intensities.

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Blue light sensitivity of melatonin suppression and subjective mood and alertness responses in humans is recognized as being melanopsin based. Observations that long-wavelength (red) light can potentiate responses to subsequent short-wavelength (blue) light have been attributed to the bistable nature of melanopsin whereby it forms stable associations with both 11-cis and all-trans isoforms of retinaldehyde and uses light to transition between these states. The current study examined the effect of concurrent administration of blue and red monochromatic light, as would occur in real-world white light, on acute melatonin suppression and subjective mood and alertness responses in humans. Young healthy men (18-35 years; n = 21) were studied in highly controlled laboratory sessions that included an individually timed 30-min light stimulus of blue (λ(max) 479 nm) or red (λ(max) 627 nm) monochromatic light at varying intensities (10(13)-10(14) photons/cm(2)/sec) presented, either alone or in combination, in a within-subject randomized design. Plasma melatonin levels and subjective mood and alertness were assessed at regular intervals relative to the light stimulus. Subjective alertness levels were elevated after light onset irrespective of light wavelength or irradiance. For melatonin suppression, a significant irradiance response was observed with blue light. Co-administration of red light, at any of the irradiances tested, did not significantly alter the response to blue light alone. Under the current experimental conditions, the primary determinant of the melatonin suppression response was the irradiance of blue 479 nm light, and this was unaffected by simultaneous red light administration.

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Human Nonvisual Responses to Simultaneous Presentation of Blue and Red Monochromatic Light

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