On the last leg of my European Tour in Sweden, I was so impressed by the searching questions from the audience. I didn’t know the answers and wondered if these might be questions you have pondered too.
So here are three for the geeks this week 😉
When you say melanopsin is sensitive to light, what exactly do you mean?
All the light-sensing cells in the rods and cones in the back of the eye contain light-sensing proteins. Each protein is linked to a light-sensitive molecule known as a chromophore. Chromophores change shape or flex in response to light energy or photons, tuned to respond optimally to a particular wavelength. This flexing action opens a gate in the cell membrane, triggering a cascade of signals. These are filtered and sorted as they are passed along to the top layer, known as retinal ganglion cells. This is the final relay station before transmission along the optic nerve and back to the brain. Around 5% of the cells in this top layer are light-sensitive in their own right – that is, they have a light-sensitive protein called melanopsin that is bonded to a chromophore that is also found in many other parts of the body – and the animal kingdom. Unlike the channel-opening action of the proteins in the rods and cones, the melanopsin complex locks the channel down, a response known as hyperpolarisation.
I love a scientific paper that has the confidence to say ‘unknown’! – Melanopsin phototransduction: beyond canonical cascades.
Isn’t a window good enough?
A window, ideally with a view of greenery, will help you to focus at work and to sleep at night. – Access to Daylight and Views Improves Physical and Emotional Wellbeing of Office Workers: A Crossover Study. It will even make you more likely to get some exercise and increase your chances of getting a promotion – Good Places to Live and Sleep Well: A Literature Review about the Role of Architecture in Determining Non-Visual Effects of Light.
Daylit buildings are also more energy-efficient by a factor of up to 60%, especially if the solution includes simple sensors to power down the lights when there’s enough natural light – Assessing Lighting Energy Saving Potential from Daylight Harvesting in Office Buildings Based on Code Compliance & Simulation Techniques: A Comparison. But you don’t need to install special sensors: when the lights are set to a default ‘off’ setting so that people switch on the lights when they need it can reduce consumption by over 17% – Improving lighting energy efficiency through user response.
The problem is that most windows are designed to stop the building heating up.
That means blocking out big chunks of the wavelengths that your body and brain need.
For example, ultra-violet is critical for vitamin D synthesis which is the flexible blue for your brain. Infra-red is key to the ability of your cells to transform food into useful components for construction and repair.
The next generation of window technology uses electrically charged particles in the body of the glass to tune the window to let in the wavelengths we want, opening the door (or the window) to buildings that balance the needs of people and planet – Material would allow users to ‘tune’ windows to block targeted wavelengths of light , Dual-Band Electrochromism in Hydrous Tungsten Oxide.
How do SAD lamps work?
Bright light therapy is pretty well-established as a treatment for seasonal affective disorder and even seems to be protective for some – by up to 36% – Bright Light as a Personalized Precision Treatment of Mood Disorders.
But what’s actually going on?
For the first time in history, we can actually see the part of the brain thamood-regulating circuits responding to signals from the ipRGCs. Bright light produces a spike in this pathway – at around the levels delivered by a well-designed SAD lamp – 10,000 lux for around 30 minutes – Illuminating a path from light to depression.
This paper also shows the critical role of a regular day-night cycle of light and darkness on this response. Disruption to the pattern leads to a chaotic signalling sequence. This in turn leads to depression of the strength of the cycle and the low mood that so many of us feel in the darker months – Daily changes in light influence mood via inhibitory networks within the thalamic perihabenular nucleus.
Bottom line? Use a SAD lamp at the same time every day and imagine your mood hormones taking a walk in the sun – Bright Light as a Personalized Precision Treatment of Mood Disorders.
ps/ don’t forget to switch off the computer and connect with friends and family – one of the most effective protective strategies against those winter blues – Who is more prone to depression at higher latitudes? Islanders or mainlanders?