Telling the time of day by color
Research by scientists at The University of Manchester has revealed
that the colour of light has a major impact on how the brain clock
measures time of day and on how the animals' physiology and behavior
adjust accordingly. The study, for the first time, provides a neuronal
mechanism for how our internal clock can measure changes in light colour
that accompany dawn and dusk.
In research publishing on April 17th in the Open Access journal
PLOS Biology, the researchers looked at the change in light around
dawn and dusk to analyze whether colour could be used to determine time
of day. Besides the well-known changes in light intensity that occur as
the sun rises and sets, the scientists found that during twilight light
is reliably bluer than during the day.
The researchers next recorded electrical activity from the brain
clock while mice were shown different visual stimuli. They found that
many of the neurons were more sensitive to changes in colour between
blue and yellow than to changes in brightness.
The scientists then simulated an artificial sky that recreated the
daily changes in colour and brightness, as they were measured at the top
of the University's Pariser Building for more than a month. As expected
for nocturnal animals, when mice were placed under this artificial sky
for several days, the highest body temperatures occurred just after
dusk, when the sky turned a darker blue, indicating that their body
clock was working optimally. If only the brightness of the sky was
changed, with no change in colour, the mice became more active before
dusk, demonstrating that their body clock wasn't properly aligned to the
day-night cycle.
Dr Timothy Brown from the Faculty of Life Sciences led the research:
"This is the first time that we've been able to test the theory that
colour affects our body clock in any mammal. It has always been very
hard to separate the change in colour to the change in brightness but
using new experimental tools and a psychophysics approach we were
successful."
He continues: "What's exciting about our research is that the same
findings can be applied to humans. So, in theory, colour could be used
to manipulate our clock, which could be useful for shift workers or
travellers wanting to minimise jet lag."
Please mention PLOS Biology as the source for this article
and include the links below in your coverage to take readers to the
online, open access articles.
All works published in PLOS Biology are open access, which
means that everything is immediately and freely available. Use this
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publication:
http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002127
Contact:
Press Officer:
Morwenna Grills
Media Relations Officer
Faculty of Life Sciences
The University of Manchester
Tel: +44 161 275 2111
Mob: +44 7920 087466
morwenna.grills@manchester.ac.uk
Author:
Dr Tim Brown
The University of Manchester
Telephone: +44161 275 5721
Timothy.Brown@manchester.ac.uk
Citation: Walmsley L, Hanna L, Mouland J, Martial F, West A,
Smedley AR, et al. (2015) Colour As a Signal for Entraining the
Mammalian Circadian Clock. PLoS Biol 13(4): e1002127.
doi:10.1371/journal. pbio.1002127
Funding: Funded by Biotechnology and Biological Sciences Research
Council (http://www.bbsrc.ac.uk)
grants BB/I017836/1 (TMB), BB/I018654 /1 (DAB) and European Research
Council (http://www.erc.europa.eu)
Melovision (RJL). The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the
manuscript
Competing Interests: The authors have declared that no competing
interests exist.
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