The Sun Shines Bright on Your Brain

The intricacies of the effect of light on cognitive functions

The sun is back! It’s time for barbecues and picnics and lazing around in the grass. What if spending time in the sun was beneficial for the mind and body? Taking in the sunlight can affect our mood but also our cognitive abilities - even as a fetus or for blind people. How can that happen? Here are some experiments that help reveal the powerful effect light has on our brain.

The sun is back! It’s time for barbecues and picnics and lazing around in the grass. What if spending time in the sun was beneficial for the mind and body? Taking in the sunlight can affect our mood but also our cognitive abilities - even as a fetus or for blind people. How can that happen? Here are some experiments that help reveal the powerful effect light has on our brain.

Cet article existe également en français :  Un éclairage sur les effets du soleil sur le cerveau

(Flickr / kuddlyteddybear2004)

Spring is here! The sun, the flowers, the birds and the bees…everything comes back to life, buzzing with joy and happiness, celebrating the return of the sun. Turns out, the nice seasons coming back affects us, humans, more than we can imagine, and even before birth.

Professor Spiro P. Pantozatos from Columbia University in New York showed that the season of birth of an individual is imprinted in his brain. He looked at 536 brains and observed a difference in size of the grey matter in the left temporal gyrus of the brain correlating with the season of birth of the individuals, especially in men. The volume of grey matter of that region was larger for births in fall/winter, with a peak at Christmas and a minimum on the 25th of June. The other way around also works: when he looked at the brains of individuals, he could guess, with better-than-chance results their season of birth, especially in women. Before we go any further, let’s clarify that more brain does not mean more intelligence. So don’t start bragging, Christmas babies.

The left temporal gyrus includes the auditory cortex and the Wernicke’s area of the brain, which is very important for language comprehension and social cognition, such as decrypting emotions on a face. So, less grey matter in that area might mean a bit more difficulties in social skills. Turns out schizophrenia is often associated with a decrease in the volume of grey matter in that precise area, and there are more schizophrenics, as well as bipolar individuals, born in spring. But all that might just be a coincidence. And just because you are born in spring doesn’t mean you are going to be socially deprived.

The author of this study suggests that these seasonal differences in brain volume might be linked with the amount of light the fetus gets during what we call the perinatal photoperiod. Light interacts with developmental genes before birth via other genes involved in the circadian clock. This might have consequences on the structure of the brain, visible years later. 

Wait, could this study give support to astrology and the signs of the zodiac…? Maybe, maybe not, but what it does say is that the amount of light we are getting could be causing fundamental changes in the brain. However, does light affect us that much on a day-to-day basis?

(Flickr / Pafgadget)

A study conducted at Brigham and Women’s Hospital in Boston, in the US, showed that prolonged exposure to blue light, specifically, had a stimulating effect. The short wavelength light could fight fatigue night and day, increasing alertness and performance. After 6.5 hours of exposure, the subjects rated themselves as feeling less sleepy and had quicker reaction times. Electrodes on the patients even revealed that the brain activity patterns showed fewer lapses in attention and shifted to a more alert state. Swedish studies even showed that people exposed to blue light did better than people under the influence of 240mg of caffeine at staying focused and maintaining accuracy when faced with different visual distractions. Overall, they had better visual reactions. Why don’t you ditch your morning coffee for a sunbath instead?

“These results contribute to our understanding of how light impacts the brain and opens up a new range of possibilities for using light to improve human alertness, productivity and safety in a work environment,” explains Steven Lockley, senior investigator of the study.

(Flickr / Irish Typepad)

So, light is really important. It stimulates daytime-like brain activity, improves alertness and mood and enhances performance in many cognitive tasks. This begs the question: What about blind people, are they disadvantaged? A study also lead by Steven Lockley shows that, actually, not seeing doesn’t necessarily mean not sensing light. Light can stimulate brain activity even in totally blind patients.

The brain is capable of “seeing” or, rather, detecting light via other types of photoreceptors than the regular “visual ones”. Called intrinsically photosensitive retinal ganglion cells, they create a non-conscious awareness of the light, which affects the same brain patterns associated with attentiveness as in sighted people.

So there you go, blind or not, go sit in the sun and enjoy the return of the light!