Fear of the dark: new studies reveal the cause

Some researchers are investigating what effects light has on emotion processing and the brain. In fact, brightness plays an important role in human physiology.

Between a dark street and a lighted alley, almost everyone would rather take the brighter path. That's because light plays an important role in human physiology. Numerous studies have identified that it can affect the brain's fear and emotion processing center, in the area called the amygdala. Specifically, researchers from Monash University and Australian Catholis University devised an experiment using functional magnetic resonance imaging to study how light affects amygdala activity.

Fear of the dark linked to amygdala functioning

The research was published in Plos One and the researchers found that a moderate amount of light tends to suppress amygdala activity more than dim light. This could explain why darkness causes us to fear. This might explain why darkness might cause us to be afraid. The study involved 24 participants who underwent fMRI while exposed to moderate light (100 lux) or dim light (10 lux). The MRI allowed the researchers to see the brain areas that were activated in real time and to observe changes in blood flow in the brain.

The researchers found that when the participants were exposed to moderate light, their amygdala activity was lower than when they were exposed to dim light. In addition, the amygdala is also connected to a region of the brain called the ventromedial prefrontal cortex (vmPFC) that is involved in processing risk, emotional responses and fear. This brain region plays an important role in regulating amygdala activity particularly with regard to suppressing emotional responses.

The study authors found that not only does light directly suppress amygdala activity, but it also appears to increase connectivity between the amygdala and the ventromedial prefrontal cortex, which would explain why light has positive effects on emotion regulation. "Light is an effective therapeutic tool for mood problems. We have shown that weak to moderate light suppresses amygdala activation," the researchers wrote, "and improves amygdala-vmPFC connectivity. These effects may directly contribute to improved mood through better emotional processing and a reduction in fear-related emotions."

To clarify the exact mechanism, by which light suppresses amygdala activity and increases connectivity to the ventromedial prefrontal cortex, more research is needed, but the study seems to demonstrate quite clearly why humans are more afraid in the dark than in the light. Staying on the subject of darkness, Australian and European researchers have instead developed a very thin film that could allow people to see in the dark.

Stefania Bernardini