Unpicking the rainbow

Unravelling the rainbow

Your brain can’t tell which wavelengths are coming out of a light source, just as you can’t always tell what ingredients went into a meal.

But fascinating new research shows how specific components of our diet of light drive critical signalling pathways in real time. This has clear implications for the next generation of lighting technologies, especially for people who don’t get these wavelengths from natural daylight.

Just one minute of blue, green, or red light exposure triggers changes in functional connectivity in both visual and non-visual brain areas – Functional connectivity of brain networks with three monochromatic wavelengths: a pilot study using resting-state functional magnetic resonance imaging

• Blue: global decrease in functional connectivity in all but the salience, orattention networks
• Green: global increase in all networks but especially in the left hemisphere (associated loosely with language, comprehension and motor control)
• Red: lower connectivity in the attentional networks and increased connectivity in the default mode networks – associated with internal processes such as remembering, thinking about the future, and allowing your mind to wander.

Seeing Red?

Far Red and Near Infra-Red light therapies are used to increase blood and metabolism in the brain, promote cell growth and repair and even help to reduce onset and severity of myopia – Light Signaling and Myopia Development: A Review

But a fascinating new paper reveals some of the mechanisms involved.  

Red light is linked to increased metabolism in mitochondria- the ‘mini generators’ in your cells that transform energy from food into a form your cells can use. Red light increases mitochondrial respiration which in turn reduces glucose levels in the body. Interestingly, Blue light does the opposite: it reduces respiration which in turn leads to a rise in glucose levels – Systemic glucose levels are modulated by specific wavelengths in the solar light spectrum that shift mitochondrial metabolism

Calming Chlorophyll?

We intuitively know that a view of nature is good for your mood – and the science backs this up  On the relation between a green and bright window view and length of hospital stay in affective disorders. It turns out these effects extend to our levels of stress, experience of pain and can even help to relieve migraines.

• Green was the only light (compared to red, blue and yellow) that didn’t increase skin conductance – a simple test of arousal –Continuous coloured light altered human brain haemodynamics and oxygenation assessed by systemic physiology augmented functional near-infrared spectroscopy
• Eye surgery patients treated with a green laser felt significantly less pain than those treated with a red one – Pain Perception at Laser Treatment of Peripheral Retinal Degenerations With Green and Infrared Wavelengths.
• Narrow Band Green light can even help with painful migraines, which in turn improves sleep and mood as this study suggests – Narrow band green light effects on headache, photophobia, sleep, and anxiety among migraine patients: an open-label study conducted online using daily headache diary

The key could be in the cones as green wavelengths seem to trigger the lowest amplitude response – Migraine photophobia originating in cone-driven retinal pathways 

Blue in the brain.

You probably know that bright blue light triggers an acute altering response.

For the first time, scientists have tracked that hotline in action. You can see the parts of the brain involved in attention on the left and the increased connectivity of this axis in response to blue light compared to baseline and the orange light control – Light modulates task-dependent thalamo-cortical connectivity during an auditory attentional task

It’s tempting to focus on these narrow-band effects as miracle cures. But just as with our diet, there is no substitute for the subtle power of natural sunlight with its perfectly calibrated spectrum that extends far beyond the range that our eyes are equipped to register.

It’s cold and damp out there. All the more reason to get outside to give your brain a rainbow-powered break.