Light has often been correlated with mood. For many, the shorter winter days and increased time spent indoors with harsh artificial lighting can lead to feelings of depression, clearly indicating that both the quantity and the quality of light we’re exposed to can have a noticeable impact on how we think and feel. But how and why does the light we take in affect our frame of mind?
In an attempt to answer these questions, a Brown University research team looked to the neural pathway connecting intrinsically photosensitive retinal ganglion cells to the prefrontal cortex of the brain, known to be involved in cognitive processing and mood regulation (1). The researchers asked a group of subjects to complete an auditory task while exposed to different levels of light intensity for 30-second periods, wearing specialized goggles that both diffused light and eliminated visual shapes, colors, and objects within the environment.
Looking at functional MR images obtained as the participants completed the exercise allowed the researchers to identify 26 human brain regions that either monotonically decreased or increased with light intensity. This luxotonic-related activation happened across the cerebral cortex, in diverse subcortical structures, and in the cerebellum. The researchers found that light suppressed prefrontal cortex activity in proportion to light intensity and that those light-evoked prefrontal cortex responses and their changes as a result of prior light exposure resembled those seen in the intrinsically photosensitive retinal ganglion cells.
The results suggest that there is a functional link between light exposure and cognitive and emotional responses mediated by the prefrontal cortex. It appears that light can really brighten your outlook – in more ways than one!
References
- S Sabbah et al., PNAS, 119, e2118192119 (2022). DOI: 10.1073/pnas.2118192119.
