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Colour as a signal for entraining the mammalian circadian clock.

Walmsley L, Hanna L, Mouland J, Martial F, West A, Smedley AR, Bechtold DA, Webb AR, Lucas RJ, Brown TM - PLoS Biol. (2015)

Bottom Line: Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance.Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions.Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.

ABSTRACT
Twilight is characterised by changes in both quantity ("irradiance") and quality ("colour") of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue-yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision.

No MeSH data available.


Related in: MedlinePlus

Spectral composition of ambient illumination is predictive of solar angle.(A) Mean (±SD) total optical power of ambient illumination around dawn/dusk as a function of solar angle relative to horizon (n = 36 d, Aug–Sep 2005; Lat.: 53.47, Long.: -2.23, Elevation 76 m). (B, top) Normalised mean spectral power distribution observed at solar angles ±6° relative to horizon. Note relative enrichment of short-wavelength light at negative solar angles. Bottom panel shows mouse ultraviolet and medium wavelength sensitive (UVS and MWS) cone opsin sensitivity profiles after correction for prereceptoral filtering. (C) Mean (±SD) “yellow–blue” colour index (effective activation of MWS/UVS opsin) as a function of solar angle around dawn/dusk. (D) Relationship between colour and irradiance (see Methods for definition), corrected according to mean for each solar angle (n = 994; -7 to 0° in 0.5° bins × 71 dawn/dusk observations; for clarity, six observations with especially high relative brightness (2.6–4.5) but normal colour (1.3–1.5) are not shown in the scatter plot). Note tighter distribution for relative “colour” versus irradiance. The data used to make this figure can be found in S1 Data.
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pbio.1002127.g001: Spectral composition of ambient illumination is predictive of solar angle.(A) Mean (±SD) total optical power of ambient illumination around dawn/dusk as a function of solar angle relative to horizon (n = 36 d, Aug–Sep 2005; Lat.: 53.47, Long.: -2.23, Elevation 76 m). (B, top) Normalised mean spectral power distribution observed at solar angles ±6° relative to horizon. Note relative enrichment of short-wavelength light at negative solar angles. Bottom panel shows mouse ultraviolet and medium wavelength sensitive (UVS and MWS) cone opsin sensitivity profiles after correction for prereceptoral filtering. (C) Mean (±SD) “yellow–blue” colour index (effective activation of MWS/UVS opsin) as a function of solar angle around dawn/dusk. (D) Relationship between colour and irradiance (see Methods for definition), corrected according to mean for each solar angle (n = 994; -7 to 0° in 0.5° bins × 71 dawn/dusk observations; for clarity, six observations with especially high relative brightness (2.6–4.5) but normal colour (1.3–1.5) are not shown in the scatter plot). Note tighter distribution for relative “colour” versus irradiance. The data used to make this figure can be found in S1 Data.

Mentions: As expected, these measurements revealed highly predictable changes in both irradiance and spectral composition as a function of solar angle (Fig 1A and 1B). In particular, we observed a progressive enrichment of short-wavelength light across negative solar angles: a result of the increasing amount of ozone absorption and consequent Chappuis band filtering of green–yellow light when the sun was below the horizon [14].


Colour as a signal for entraining the mammalian circadian clock.

Walmsley L, Hanna L, Mouland J, Martial F, West A, Smedley AR, Bechtold DA, Webb AR, Lucas RJ, Brown TM - PLoS Biol. (2015)

Spectral composition of ambient illumination is predictive of solar angle.(A) Mean (±SD) total optical power of ambient illumination around dawn/dusk as a function of solar angle relative to horizon (n = 36 d, Aug–Sep 2005; Lat.: 53.47, Long.: -2.23, Elevation 76 m). (B, top) Normalised mean spectral power distribution observed at solar angles ±6° relative to horizon. Note relative enrichment of short-wavelength light at negative solar angles. Bottom panel shows mouse ultraviolet and medium wavelength sensitive (UVS and MWS) cone opsin sensitivity profiles after correction for prereceptoral filtering. (C) Mean (±SD) “yellow–blue” colour index (effective activation of MWS/UVS opsin) as a function of solar angle around dawn/dusk. (D) Relationship between colour and irradiance (see Methods for definition), corrected according to mean for each solar angle (n = 994; -7 to 0° in 0.5° bins × 71 dawn/dusk observations; for clarity, six observations with especially high relative brightness (2.6–4.5) but normal colour (1.3–1.5) are not shown in the scatter plot). Note tighter distribution for relative “colour” versus irradiance. The data used to make this figure can be found in S1 Data.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401556&req=5

pbio.1002127.g001: Spectral composition of ambient illumination is predictive of solar angle.(A) Mean (±SD) total optical power of ambient illumination around dawn/dusk as a function of solar angle relative to horizon (n = 36 d, Aug–Sep 2005; Lat.: 53.47, Long.: -2.23, Elevation 76 m). (B, top) Normalised mean spectral power distribution observed at solar angles ±6° relative to horizon. Note relative enrichment of short-wavelength light at negative solar angles. Bottom panel shows mouse ultraviolet and medium wavelength sensitive (UVS and MWS) cone opsin sensitivity profiles after correction for prereceptoral filtering. (C) Mean (±SD) “yellow–blue” colour index (effective activation of MWS/UVS opsin) as a function of solar angle around dawn/dusk. (D) Relationship between colour and irradiance (see Methods for definition), corrected according to mean for each solar angle (n = 994; -7 to 0° in 0.5° bins × 71 dawn/dusk observations; for clarity, six observations with especially high relative brightness (2.6–4.5) but normal colour (1.3–1.5) are not shown in the scatter plot). Note tighter distribution for relative “colour” versus irradiance. The data used to make this figure can be found in S1 Data.
Mentions: As expected, these measurements revealed highly predictable changes in both irradiance and spectral composition as a function of solar angle (Fig 1A and 1B). In particular, we observed a progressive enrichment of short-wavelength light across negative solar angles: a result of the increasing amount of ozone absorption and consequent Chappuis band filtering of green–yellow light when the sun was below the horizon [14].

Bottom Line: Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance.Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions.Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.

ABSTRACT
Twilight is characterised by changes in both quantity ("irradiance") and quality ("colour") of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue-yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision.

No MeSH data available.


Related in: MedlinePlus