Ever feel like you’re having a bad day, then the sun comes out and suddenly you’re more upbeat? Or perhaps a winter day you thought you were really sad — just around the time the sun began setting at 4 p.m.? It’s no secret that daylight significantly influences mood. Brown University researchers studying light therapy may be able to explain why.
In a new study, researchers used functional MRI in 20 healthy adults to examine how light-intensity sends signals to the brain, and also how it processes mood as a response. Participants viewed four different levels of light intensity for 30 seconds each through goggles that diffused light and excluded shapes, colors, and other objects. The intensities ranged from dark to bright.
The study finds that some regions of the cerebral cortex involved in cognition and mood show intensity-dependent sensitivity. Also, in assessing the brain scans, researchers identified 26 different human brain regions where activity either decreased or increased in response to light-intensity.
These discoveries have the potential to unravel a deeper understanding of mood disorders.
“Identifying this pathway and understanding its function might directly promote development of approaches to treat depression, either by pharmacological manipulations or non-invasive brain stimulation in selected nodes of the pathway or with targeted bright-light therapy,” says the lead study author Jerome Sanes, a Brown professor of neuroscience affiliated with the University’s Carney Institute for Brain Science, in a statement.
These findings build off existing research conducted by study co-author David Berson, a Brown neuroscience professor. In 2002, he discovered unique light-sensing cells within the eye. Interestingly, he found that they aren’t involved in viewing objects or forms, just light sensitivity. His research also found that some animals have mood-regulating pathways that link these cells to areas in the prefrontal cortex with mood disorders.
Sanes says that this latest study was designed to investigate if this same pathway was seen in humans, and with similar functionality. Sanes and his team were able to show that the pre-frontal regions have similar signals. “The findings from our study offer a functional link between light exposure and prefrontal cortex-mediated cognitive and affective responses,” says Sanes.
For next steps, Sanes and his team have several questions that they hope to find answers to. “How does that compare to a control group of healthy people not diagnosed with these disorders?” he asked. “Does light activate the same regions, and if so, are these regions more or less sensitive to light activation? What is the magnitude of difference in the effect? This is an area of ongoing investigation,” he said.
The researchers express that this is an area that requires ongoing research and investigation, especially as it provides implications for mood disorder treatments.
This study is published in the journal Proceedings of the National Academy of Science.