osed to 10-minute blasts of either blue (at 461 nm) or orange light (at 589 nm – strictly speaking, quite a yellowy orange light). They were blindfolded at all times when not undergoing light exposures or their scan and brain tasks.
The researchers were able to show that executive brain responses were influenced by the wavelength of the light to which individuals were exposed some 70 minutes prior to each recording. Prior exposure to the longer wavelength orange light enhanced the subsequent impact of the test light – the subjects showed greater brain activity in several regions of the frontal lobes related to alertness and cognition – while prior exposure to the shorter wavelength blue light had the reverse outcome.
“This wavelength-dependent impact of prior light exposure is consistent with recent theories of the light-driven melanopsin dual states. Our results emphasize the critical role of light for cognitive brain responses and are, to date, the strongest evidence in favour of a cognitive role for melanopsin, which may confer a form of ‘photic memory’ to human cognitive brain function,” write the researchers in their published paper.
In a press release from INSERM, the researchers write, “Ultimately, these findings argue for the use and design of lighting systems to optimize cognitive performance.” Given melanopsin’s cognitive effects, perhaps the concept of ‘smart’ lighting systems in schools and universities has a whole new meaning.
The research was published online ahead of print on 10 March 2014 in the journal Proceedings of the National Academy of Sciences (PNAS).
Chellappa, S.L., Ly, J.Q.M., Meyer, C., Balteau, E., Degueldre, C., Luxen, A., Phillips, C., Cooper, H.M. and Vandewalle, G. (2014). Photic memory for executive brain responses. PNAS (In press): 1320005111v1-201320005. Published online ahead of print 10 March 2014. www.pnas.org/content/early/2014/03/07/1320005111.abstract