Bedrosian TA, Nelson RJ (2017) Timing of light exposure affects mood and brain circuits. Transl Psychiatry 7, e1017-e1017.
Our bodies operate on a circadian rhythm. Interruption to this rhythm by means of unnatural exposure to light can cause negative physiological effects on the body. Light activates factors that are essential for the regulation of mood and overall brain health.
Choi K, Suk H-J (2016) Dynamic lighting system for the learning environment: performance of elementary students. Opt Express 24, A907-A916.
Learning and memory are influenced by circadian rhythm. Brains are primed to learn new info during the day when there is a lot of light and then to consolidate and store it when we sleep during the dark. This study showed that student performance increased when classrooms were illuminated with bright (blue-rich) light.
Figueiro MG, Plitnick BA, Lok A et al. (2014) Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities. Clin Interv Aging 9, 1527-1537.
This study found that the implementation of bright light therapy in the morning combined with reduced light exposure in the evening improved memory consolidation during sleep and mood. It also reduced agitation in patients with dementia.
Inami S, Sato S, Kondo S et al. (2020) Environmental Light Is Required for Maintenance of Long-Term Memory in Drosophila. The Journal of Neuroscience 40, 1427-1439.
Light activates factors that are essential for memory formation.
Based on this, we are getting at least 1000 times less light during the day and at least 100 times too much light at night. Additionally, the color distribution of most artificial lights is constant.
Smolensky MH, Sackett-Lundeen LL, Portaluppi F (2015) Nocturnal light pollution and underexposure to daytime sunlight: Complementary mechanisms of circadian disruption and related diseases. Chronobiology International 32, 1029-1048.
Alterations to the circadian rhythm from off schedule light exposure disrupts hormone production, and can lead to an elevated stress response and mood disorders. For example, less melatonin may be produced, causing insomnia.
Soler JE, Robison AJ, Núñez AA et al. (2018) Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat (Arvicanthis niloticus). Hippocampus 28, 189-200.
This study showed that when animals are exposed to constant dim light, instead of the natural cycle of bright light and darkness, they show impairments in learning and memory. They studied nile grass rats and found that hippocampal structural plasticity was a major factor that was altered.
van Lieshout-van Dal E, Snaphaan L, Bongers I (2019) Biodynamic lighting effects on the sleep pattern of people with dementia. Building and Environment 150, 245-253.
Indoor lights should be bright and blue during the day and red at night.
Vandewalle G, Balteau E, Phillips C et al. (2006) Daytime Light Exposure Dynamically Enhances Brain Responses. Current Biology 16, 1616-1621.
Bright light exposure activates regions of the brain that promote alertness, and improves cognitive performance.
Alkozei A, Smith R, Pisner DA, Vanuk JR, Berryhill SM, Fridman A, Shane BR, Knight SA, Killgore WD. Exposure to Blue Light Increases Subsequent Functional Activation of the Prefrontal Cortex During Performance of a Working Memory Task. Sleep. 2016 Sep 1;39(9):1671-80.
This study focused on whether blue wavelengths of light have an effect on cognitive performance. In the study, participants were exposed to 469nm blue light or 578nm amber light for 30 minutes. After, they performed a working memory task while simultaneously being under an fMRI. The study found that the blue light condition was correlated with a quicker response time in the task as well as increased activation in the dorsolateral and ventrolateral prefrontal cortex. An important implication of this study is that blue-enriched light can be used in academic or work settings to increase performance in tasks that require individuals to be alert and quick in decision-making.
Mott, M. S., Robinson, D. H., Walden, A., Burnette, J., & Rutherford, A. S. (2012). Illuminating the Effects of Dynamic Lighting on Student Learning. SAGE Open, 2(2).
Past studies have shown that different aspects of lighting such as temperature and illumination can affect sleep, mood, focus motivation, concentration, and work/school performance. The implications of these studies have been artificial light systems that help humans perform tasks more efficiently by altering the light environment. In this study, 84 third graders were exposed to either focus (6000K-100fc average maintained) or normal lightning. Students exposed to focus lighting showed a higher oral reading fluency performance than did those with control lighting.
Fernandez, D. C., Fogerson, P. M., Ospri, L. L., Thomsen, M. B., Layne, R. M., Severin, D., ... & Hattar, S. (2018). Light affects mood and learning through distinct retina-brain pathways. Cell, 175(1), 71-84.
This article discusses how light affects learning and mood by focusing on the intrinsically photosensitive retinal ganglion cells. The effects of light involve a pacemaker-independent role for the suprachiasmatic nucleus as well as the perihabenular nucleus in the thalamus. The article also discusses specific circuitry in the neuroanatomy of the brain that causes these effects of light.
Burke, T. M., Scheer, F. A., Ronda, J. M., Czeisler, C. A., & Wright Jr, K. P. (2015). Sleep inertia, sleep homeostatic and circadian influences on higher‐order cognitive functions. Journal of sleep research, 24(4), 364-371.
Sleep inertia, sleep homeostatic and circadian processes modulate cognition, including reaction time, memory, mood, and alertness. In the study there were 6 participants who participated in a 73-day-long study. The duration included two 14-day-long 28-hour forces desynchrony protocols. The purpose was to examine separate and interacting influences of sleep inertia, sleep homeostasis and circadian phase on higher-order cognitive functions of inhibitory control and selective visual attention. Cognitive performance for most measures was impaired immediately after scheduled awakening and improved during the first 2-4 hours of wakefulness (decreased sleep inertia). It worsened until scheduled bedtime (increasing sleep homeostasis). The relative influences of sleep inertia, sleep homeostasis and circadian phase depended on the specific task examined. Inhibitory control was modulated most strongly by circadian phase. Selective visual attention for a spatial-configuration search task was modulated most strongly by sleep inertia. The findings demonstrate that some higher-order cognitive processes are differentially sensitive to different sleep-wake regulatory processes. Differential modulation of cognitive functions by different sleep-wake regulatory processes has important implications for understanding mechanisms contributing to performance impairments during adverse circadian phases, sleep deprivation and /or upon awakening from sleep.
Vandewalle, G., Schmidt, C., Albouy, G., Sterpenich, V., Darsaud, A., Rauchs, G., ... & Dijk, D. J. (2007). Brain responses to violet, blue, and green monochromatic light exposures in humans: prominent role of blue light and the brainstem. PloS one, 2(11), e1247.
In this study, researchers exposed participants to short duration monochromatic light of varying wavelengths (violet, blue, and green) during a working memory task. At onset of light, blue light (compared to green light) increased activity in the left hippocampus, left thalamus, and right amygdala. During the task, blue light (compared to violet light) also increased activity in the left middle frontal gyrus, left thalamus, and a bilateral area of the brainstem related to the activation of the locus coeruleus. The results support that melanopsin-expressing retinal ganglion cells contribute to brain responses to light during exposure. It also shows the role the brainstem plays in mediating the responses.
This paper seemed to zoom in to a specific aspect of light exposure by looking at more wavelengths of light, including violet.
Vandewalle, G., Balteau, E., Phillips, C., Degueldre, C., Moreau, V., Sterpenich, V., ... & Maquet, P. (2006). Daytime light exposure dynamically enhances brain responses. Current Biology, 16(16), 1616-1621.
In this study, researchers used fMRI to characterize the neural correlates of the alerting effect of daytime light. To do this, they exposed individuals to a short exposure of bright white light, and assessed the responses to an auditory oddball task. Light-induced improvement in alertness was correlated with responses in the posterior thalamus. Light also enhanced responses in cortical areas related to attention and decreased diminutions of activity typically observed during darkness. It was also shown that responses to light declined within minutes after differing region-specific time courses. Their findings suggest that light can modulate activity of subcortical structures related to alertness, promoting cortical activity in networks related to nonvisual cognitive processes. This paper zoomed in to a particular light exposure, in this case, bright white light as opposed to monochromatic light.
Vandewalle, G., Gais, S., Schabus, M., Balteau, E., Carrier, J., Darsaud, A., ... & Maquet, P. (2007). Wavelength-dependent modulation of brain responses to a working memory task by daytime light exposure. Cerebral cortex, 17(12), 2788-2795.
This paper looked at the effects of melanopsin-expressing light-sensitive ganglion cells which are highly sensitive to blue light. Prior, there was no evidence that blue light exposure modulates nonvisual brain activity related to complex cognition. In the study, the researchers use fMRI to show that a short daytime exposure to blue or green monochromatic light differentially modulates regional brain responses during an auditory working memory task. It was shown that blue light usually enhanced brain responses in frontal and parietal cortices as well as the thalamus, while green light typically declined brain responses. The general results of the study are that monochromatic light can affect cognition almost instantaneously and these effects are mediated by a melanopsin-based photoreceptor system. This paper set a general framework to build upon by showing that melanopsin-expressing light-sensitive ganglion cells play a large role in the relationship between light exposure and cognition.
Aggleton, J. P., Hunt, P. R., & Rawlins, J. N. P. (1986). The effects of hippocampal lesions upon spatial and non-spatial tests of working memory. Behavioural brain research, 19(2), 133-146.
An, M., Huang, J., Shimomura, Y., & Katsuura, T. (2009). Time-of-day-dependent effects of monochromatic light exposure on human cognitive function. Journal of physiological anthropology, 28(5), 217-223.