Brain: bright light boosts alertness

Do you need a pick-me-up? Focus on light. A study from the University of Liège reveals that exposure to high levels of light can help people feel more awake and increase their cognitive performance.

This study, published in the journal eLife on April 23, provides a better understanding of how light can affect human behavior.

Brightness and cognitive ability: the human hypothalamus does not respond uniformly

To better understand the impact of light on the human brain, scientists brought together 26 healthy young adults. They asked each of them to perform two auditory cognitive tests. The first was an executive task. Participants had to determine whether the sound they made was the same as the one they had heard twice earlier, or whether it contained the letter “K.” In the second test, they had to identify the gender of the voice while it spoke words in a neutral or angry tone. During all of these tests, individuals were alternately placed in darkness or exposed to four different levels of illumination.

Additionally, the team used seven-tesla functional magnetic resonance imaging – which offers finer resolution than a standard MRI – to assess the impact of different lighting levels on hypothalamus activity during the tests.

The scientists found that, during both tasks, the higher light levels triggered an increase in activity in the posterior hypothalamus. In contrast, the lower and anterior parts of this brain area followed a seemingly opposite pattern: They showed reduced activity under higher light levels.

“Our results demonstrate that the human hypothalamus does not respond uniformly to different light levels when engaged in a cognitive challenge”explains the main author, Gilles Vandewalle, co-director of GIGA-CRC Human Imaging in a communicated.

High light level: better test performance

The team then wanted to know if the changes in activity observed in the hypothalamus were linked to a change in cognitive performance. To answer the question, she focused on assessing participants’ performance during the executive task.

The analysis revealed that higher light levels did indeed lead to better cognitive performance, and greater arousal among participants. “It is important to note that the increase in cognitive performance in higher illumination is negatively correlated with the activity of the posterior hypothalamus. It is therefore unlikely that the activity of the posterior hypothalamus is the mediator direct impact of light on cognitive performance, and this could indicate that other brain regions are involved, which would require further research.”specify the authors in their press release.

Furthermore, activity in the posterior hypothalamus was found to be linked to better performance on the emotional task. “This suggests that the association between cognitive performance and posterior hypothalamus activity may be context dependent – ​​in some tasks, certain hypothalamus nuclei or neuronal populations may be recruited to increase performance, but not in d ‘others.”

Light therapy to improve wakefulness?

For the researchers, the results of their study could serve as a basis for various light therapy treatments aimed at improving the quality of sleep and the emotional state of a person or even helping them to feel more awake throughout the day. .
However, additional studies still need to be conducted to assess the impact of light on other brain structures, to determine how brightness may alter their interactions with the cortex.

“It is important to answer the questions raised by our study, because the action of light represents a promising and easy-to-implement way to reduce fatigue throughout the day, improve cognitive impairments and enable restful sleep with minimal cost and side effects”, explains Islay Campbell.

“Targeted lighting for therapeutic purposes is an exciting prospect. However, it will require a more complete understanding of how light affects the brain, particularly at the subcortical level”adds the expert.