Light for Life.

In this essay for an audience involved in theatrical light and mood atmospheres, I will introduce the biology of how light affects mood to help understand why light is not only aesthetic, functional, and emotional, but also deeply modulates every aspect of our physiology and behaviour. The “biology lesson” will be complemented by examples of collaborations with artists and designers who have experimented with and transformed these concepts into their own particular vision, thereby illuminating the science and making it accessible in a different way.

But the not-so-theoretical question arises here, rather bluntly: are artists really interested in science? Are they not rather seduced and inspired by the visual aspects, thus using science as a quarry for ideas? Digging deeper into scientific concepts and data requires effort and discipline¹. We are not talking about appreciating the coloured swirls of fractals or the infinite permutations of snowflake patterns, and incorporating these images into a given work. The science exists beyond the raw beauty and yields layers of surprising and practical insights. Fractals are visual mathematics, producing a ragged geometric shape whose parts are a diminished copy of the whole (see Romanesco broccoli for a perfect example)². The hexagonal symmetry of a snowflake reflects the internal order of water molecules as they arrange themselves during crystallisation. Snowflakes help understand structure formation and self-assembly. So what does the artist seek when engaging with such a scientific topic? To be in touch with nature, to interpret a piece of knowledge with one’s own subjectivity? And what does a scientist seek in art? The artist’s work brings the research greater visibility, and an outsider perspective reinvigorates the scientist’s curiosity. Creative sparks can fly when artists and scientists interact.

Dire luce

A biologist perceives and considers light in a very existential and evolutionary manner. The living organisms inhabiting our planet emerged out of molecules that captured the sun’s energy and transformed it into cells, leaves, flowers, organs, complex structures. To survive, organisms need to optimise food gathering, avoid predators, and reproduce under favourable conditions – specifically, to be prepared for the right behaviour at the right time of day or night or season³. It is not surprising that, early in evolution, the most primitive bacteria created the first simple chemical feedback loop that provided the cell with ‘internal time’. From unicells to plants to insects to vertebrates to mammals, 24-hour biological clocks have developed, which manifest an individually precise but not exactly 24-hour rhythm (“circadian” = about a day) in nearly every behaviour or function (3). These clocks drift out of phase with real time if left in constant conditions without signals from the external world. Their most important synchronising agent or “zeitgeber” (time-giver) is light⁴. 

Light enters the eye

We think of the eye primarily as the gateway to vision. Indeed, light is transmitted through the classic photoreceptors in the retina, rods and cones, to differentiate colour, images, patterns and movement. Light however has a host of non-visual functions as well, transmitted via a recently discovered class of photoreceptors called the intrinsically photosensitive retinal ganglion cells (ipRGCs) containing a photopigment, melanopsin, specifically responsive to blue wavelengths⁵. We now know that blue light stimulates alertness and delays sleep in the evening through these mechanisms⁶.

What does an artist do with this information? Here Switzerland’s most innovative textile designer, Martin Leuthold, wove two scientific images – the photoreceptors of the retina (rods, cones, and ganglion cells) and the molecular structure of the visual pigment rhodopsin (the coloured spirals) together with images from the natural world – flowers, a caterpillar, butterflies, to create foulards of great originality

These blue-tinted images represent two of the many installations and performances that developed out of a week’s workshop with sleep scientists and artists at the Sleep-Wake Centre of Massey University in New Zealand⁷. The Waking Tunnel created a bright blue alerting atmosphere over the stairs leading up to the exhibition; the dancer wore a sensor suit which detected different wavelengths of light, and movement was converted into sound of different wavelengths.

Light enters the brain

Light is transmitted from the different photoreceptors in the retina to the brain, to create vision but also non-visual responses, particularly that of the circadian clock. This clock is situated in a small area of the brain near the optic nerve, called the suprachiasmatic nuclei (SCN). Its neuronal firing rates over the 24 hours act as a master pacemaker controlling all rhythms in the body⁸. These data (and others related to chronobiology and sleep science) have been surprisingly transformed into haute couture, The Eri Matsui Spring-Summer Fashion Collection 2012, that was presented at the World Sleep Conference in Kyoto in 2011.

The importance of light for humans

This discovery of the blue-sensitive photoreceptors has had enormous consequences not only for understanding the brain but also for medicine, the lighting industry, and even architecture and urbanism⁹. Light is a zeitgeber for the biological clock, stabilises sleep, has a direct effect on mood and alertness, cognition and performance, and links our daily behaviour and emotions to the natural day-night cycle and the changing seasons. Before the invention of electric lighting, humans were primarily exposed to intense outdoor daylight and dim indoor light at night. Remember that light signals in nature are dynamic, spanning a huge range of illuminance from 0.0001 lux of starlight to 100’000 lux at midday when the sun shines. Of course daylight duration, spectra and intensity are dependent on season, latitude, and local weather. Now we spend much of our day exposed to intermediate, constant light intensities that last long into the evening. Too little bright light during the day, too much light at night. Particularly the blue-wavelengths common to computer, tablet, and phone screens is not conducive to a good night’s sleep¹⁰. So we should aim to receive enough outdoor light every morning, which is rare in today’s indoor life style, and avoid too much light at night, which is unfortunately not the case for most people¹¹. We are only slowly recognising that there may be health consequences of irregular, inadequate, and poorly timed light-dark cycles¹².

In chronobiology research we have used for decades small wrist-worn activity monitors that also record the amount of light received (today’s high-tech Fitbits), to understand sleep-wake and light-dark cycles in health and illness. These records can cover weeks and months and provide non-invasive data helpful for diagnosis. The artist Andreas Horlitz has used such activity and light monitor data for a series of light boxes and composite prints.

One can see how fascinated he was by the symbolic of human sleep-wake cycles combined with light, in the two prints using images of the sun and in the column lit up by fluorescent lightsOne can see how fascinated he was by the symbolic of human sleep-wake cycles combined with light, in the two prints using images of the sun and in the column lit up by fluorescent lights.

Very early in this research, bright light was tested as an antidepressant for winter depression or Seasonal Affective Disorder (SAD). All over the world, particularly in northern latitudes, clinical trials have provided strong evidence for the efficacy of light in SAD¹³, and also in non-seasonal depression¹⁴, geriatric depression¹⁵, and bipolar illness¹⁶. Carefully timed light therapy is an important tool in sleep medicine to resynchronise sleep to regular night times¹⁷. Light may slow down cognitive decline in Alzheimer’s dementia¹⁸ and improve some symptoms of Parkinson’s disease¹⁹. The potential clinical applications of light are vast, and still being explored.

The classic treatment is with a straightforward light box, designer lighting is rare. However, the lighting industry immediately recognised the importance of these non-visual effects of light, and developed dynamic lighting systems with changing spectra and intensity across the day to simulate naturalistic conditions (what they call “human-centric lighting”). The non-visual effects of light have been gradually incorporated into artificial lighting guidelines and standards, which until now were focused exclusively on visual comfort.

The interplay between light and sleep, alertness and mood is established and yet can still be quite experimental for an artist.

Light and architecture

Architects are also considering how buildings and urban spaces can become more (day)light-oriented²⁰. As Le Corbusier said, «Architecture is the masterly, correct and magnificent play of volumes brought together in light»²¹. In terms of a more conceptual, artistic approach, with scientific background, Philippe Rahm and Gilles Decosterd created a light room in the Swiss Pavillion of the Architecture Biennale in Venice²². The space was totally empty, just pure white light of 10’000 lux, with oxygen concentrations reduced from 21% to 14.5%, the situation one might experience on a snowy Swiss mountain peak. The intense physiological impact could be felt after only a few minutes immersion.

We assume that daylight is better than artificial light, since it is the signal that defined evolution of life on earth. But we still don’t know all the crucial characteristics of daylight that are different from the most sophisticated new lighting systems and which ones are specifically relevant for health²³.

We rarely experience indoors the passage of the sun moving across the sky and the change in daylight duration with the seasons. Colin Fournier, co-architect of the Graz Kunsthaus, explores the structure of a “sundial” circadian house, where daylight enters nozzles designed to light up each area of activity taking place at a given time of day.

Where there is light, there is also shadow, darkness, night. It is the contrast that is important in theatrical lighting and the same is true for the geophysical rhythm of day and night. The key biological signal is not the brightness of full daylight but the transitions of the twilight zone, dawn and dusk. Darkness itself can be therapeutic, for example in some sleep disorders and in clinical mania. Siegrun Appelt is an artist whose light interventions always have to do with darkness as well²⁴. 

There are so many potential ramifications of this new knowledge – not just a functional transfer to buildings or medical treatments, but also questioning our definition of aesthetics and our understanding of human, animal and plant well-being. Importantly, there are implications for developing a new “chrono-ecology” to live again in harmony with the natural environment.

 Further information on light therapy at www.cet.org and uses of daylight www.daylight.academy