Light can be used as a powerful brain stimulant

Harold Mandel's picture
A little girl having fun in the sunshine

People often find that they feel more energized with light. This offers a consideration of light as being a powerful natural stimulant which can take the place of drugs. There appears to be great potential for enhanced well being with the use of light, along with other well known natural stimulants such as green tea and ginseng.

Light has been found to be a powerful stimulant for human alertness and cognition, reported PNAS. It is significant to note that light can be easily administered to improve performance or to counteract the negative impact of sleepiness, even during the day. Researchers have observed that prior exposure to longer wavelength light, orange, relative to shorter wavelength, blue improves the subsequent impact which light has on executive brain responses.

The importance of light for human cognitive brain function is emphasized by these findings while also constituting compelling evidence in favor of a cognitive role for melanopsin. Melanopsin is a recently discovered photopigment which may provide a unique form of “photic memory” for human cognition. What these findings ultimately mean is that the integration of light exposure over long periods of time can actually help optimize cognitive brain function.

It is presumed that light acts through a photoreception system which relies very much on the photopigment melanopsin. Evidence for the association of melanopsin in light-driven cognitive stimulation remains indirect in people, due to problems with selectively isolating its contribution.

Therefore, the role for melanopsin in the regulation of human cognition remains to be firmly established. However, research has pointed to the critical role of light for cognitive brain responses with evidence in favor of a cognitive role for melanopsin, which may actually confer a form of “photic memory” to human cognitive brain function.


It has been known for a long time that light exerts powerful effects on the brain and on our well-being, reports the University of Liege. Aside from being essential for vision, light is also required for a wide range of “non-visual” functions which includes synchronization of our biological clock to the 24h day-night cycle. Also, light has been routinely used to improve performance and counter the negative impact of sleepiness or "winter blues".

Within the last decade or so, researchers have discovered melanopsin, which is a new type of light sensitive cell photoreceptor in the eye. Melanopsin is a novel photoreceptor which has been found to be an essential component for relaying light information to a set of so-called non-visual centers which are located in the brain. Animal research has showed in the absence of this photoreceptor non-visual functions are disrupted. What happens is there is a deregulation of the biological clock as it 'free-runs" independent from the 24 day-night cycle as the stimulatory influence of light is impaired. Melanopsin is maximally sensitive to blue light.

In humans the role of melanopsin in cognition and alertness has not been well established. However, researchers from the Cyclotron Research Centre of the University of Liège in Belgium and of the Department of Chronobiology of the INSERM Stem Cell and Brain Research Institute in Bron, France have recently found evidence which demonstrates the involvement of melanopsin in the impact of light on cognitive brain function.

Previous exposure an hour earlier to an orange light enhanced the subsequent impact of the test light, while previous exposure to blue light had the reverse outcome. This phenomenon of prior light effects on a subsequent response to light is typical of melanopsin as well as certain photopigments of invertebrate and plants. This phenomenon has been referred to as a "photic memory". It is therefore interesting to note that people may have an invertebrate or plant-like machinery located within the eyes which participates to regulate cognition.

The importance of light for human cognitive brain functions is emphasized by these findings. A cognitive role for melanopsin is also supported by these findings. In a more general sense what happens is the continuous change of light during the day also changes us. These findings support suggestions for the use and design of lighting systems in order to optimize cognitive performance.

People really often do appear to feel better with exposure to light. The findings in this research which offer a scientific explanation for the benefits of light for well being opens the door for a consideration of actually prescribing light therapy as part of a natural health program to help people prevent feeling run down and as a stimulant. Taking time for exposure to some stimulating light, coupled with good nutrition, some green tea and ginseng, and adequate daily exercise and rest sure beats taking drugs to improve alertness.