Brain Science

Hours Spent in Low-Level Light Physically Alter Your Brain

Back to ArticlesArticles
Hours Spent in Low-Level Light Physically Alter Your Brain about undefined
If you find yourself feeling better the last couple of weeks, it could be because spring is just around the corner. During the winter months many people suffer with Seasonal Affective Disorder (SAD). They experience persistently low moods, irritability and lethargy. The condition is thought to be linked to reduced daylight, which disrupts brain hormones and our internal body clocks. As the days get longer, spirits lift. But mood can also be influenced by the intensity of light, not just the amount of light we are exposed to. This isn't a seasonal phenomenon. It can affect us all year round. Now new research has revealed for the first time that spending too much time in subdued light not only changes the way we feel, but can actually change the structure of the brain itself. It’s a fascinating discovery.

Light Linked to Emotional Health

A number of studies reveal that mental health can be affected in some way by light. For instance, one group of female employees working in rooms with windows was compared to a similar group who spent their working day relying on artificial light. Those exposed to natural light reported fewer symptoms of depression and better quality of sleep.1 In another human study, a series of tests revealed that people feel emotions of any kind - positive or negative - with greater intensity under bright light. The initial reaction to a given stimulus appears to strengthen under such conditions.2 But what is actually happening in the brain in response to light? In their initial studies, neuroscientists from Michigan State University carried out experiments on Nile grass rats. Like humans, this breed of rat is diurnal and sleeps during the night. The researchers found increased anxiety and depression among those kept in dim versus bright daylight conditions. They also found dysregulation in the hypothalamic pituitary adrenal (HPA) axis - the primary stress response system.3 In their most recent study, published in the March edition of Hippocampus, and funded by the National Institutes of Health, the Michigan scientists exposed the rodents to either dim or bright daytime conditions for four weeks. The wavelength of light spanned a range normally encountered by humans. Both groups had also been trained to navigate a maze as a way to enable the researchers to assess spatial memory.

Vital Brain Protein Plummets in Poor Lighting

The bright light rodents demonstrated marked improvement when they were retested in the maze. But the dim light rats lost nearly one third (30%) of their capacity in the hippocampus, a region of the brain vital for memory and learning. The dim light rats also failed to perform normally on the maze test. These poor performers were returned to normal living conditions for a month before being exposed to another four weeks of light - this time, the bright kind. Their brain capacity and task performance made a full recovery.4 The researchers found that prolonged periods of time spent in ill-lit conditions caused a drop in brain-derived neurotrophic factor (BDNF), an important brain-growth protein that protects brain cells, encourages the creation of new ones, and promotes connections between neurons for better communication. BDNF is likewise vital in humans (see Issue #470.) Joel Soler, one of the authors, explained that in a dingy environment "...there are fewer connections being made. This results in diminished learning and memory performance that is dependent upon the hippocampus. "In other words, dim lights are producing dimwits." Fellow study author Antonio "Tony" Nunez added, "When we exposed the rats to dim light, mimicking the cloudy days of Midwestern winters or typical indoor lighting, the animals showed impairments in spatial learning. "This is similar to when people can't find their way back to their cars in a busy parking lot after spending a few hours in a shopping mall or movie theater."5 I think it’s likely these animal studies hold true for humans, too, given the evidence for increased depression during the winter months. It would be a good idea for all of us to make sure we work and play by natural light when we can.
  1. https://www.ncbi.nlm.nih.gov/pubmed/25424517
  2. https://www.sciencedaily.com/releases/2014/02/140220132004.htm
  3. https://www.ncbi.nlm.nih.gov/pubmed/26684510
  4. https://www.ncbi.nlm.nih.gov/pubmed/29251803
  5. http://msutoday.msu.edu/news/2018/does-dim-light-make-us-dumber

Keep Reading

View All Articles
This Part of Your Body May be the Very Heart of the Aging Process about false

Brain Science

This Part of Your Body May be the Very Heart of the Aging Process

Inside your brain, there’s a very small section of tissue that some researchers believe is the very heart of the aging process.They also think this tiny but crucially important area holds clues that

A Yawn is More Complicated – and Important to Mental Focus – Than We Think about false

Brain Science

A Yawn is More Complicated – and Important to Mental Focus – Than We Think

For the longest time, the act of yawning puzzled medical researchers. Yawning seems commonplace and insignificant – you feel tired, you yawn. You see somebody else yawn, you yawn. You get bored, you

Dousing Chronic Brain Inflammation that Leads to Alzheimer’s about false

Brain Science

Dousing Chronic Brain Inflammation that Leads to Alzheimer’s

I’ve often discussed the fact that research into Alzheimer’s disease and other types of dementia has increasingly shown how inflammation in the brain wreaks havoc on your memory.The new attention on