#Higher #Light #Levels #Improve #Cognitive #Performance
Exposure to high levels of light may help people feel more awake and increase their cognitive performance, likely by influencing the activity of parts of a brain region called the hypothalamus, according to a new study.
The study is published today in eLife and is of fundamental importance and represents a key advance in our understanding of how different levels of light affect human behavior. These findings could serve as a basis for various light therapy treatments aimed at improving a person’s sleep quality and emotional state, and helping them feel more awake and perform tasks better throughout the day. .
The biological effects of exposure to light have been well documented in recent years. Higher lighting levels have been shown to boost alertness and cognitive performance. These effects depend primarily on a subclass of light-sensitive cells in the retina, called ipRCGs. These cells travel to many areas of the brain, but the projections are denser in the hypothalamus, which is generally associated with the regulation of circadian rhythms, sleep and alertness, as well as cognitive functions. However, knowledge about the brain circuits that underlie the biological effects of light comes almost exclusively from studies in animals.
““It is difficult to translate findings about how light exposure affects the brain in animal models to humans because the later maturation of the cortex in humans allows for much more complex cognitive processing.”, explains lead author Islay Campbell, a former doctoral student at GIGA, now a Ph.D. “In particular, whether the nuclei of the hypothalamus contribute to the stimulating impact of light on cognition is not established.”.
To better understand the impact of light on human cognition, Islay Campbell and colleagues recruited 26 healthy young adults to participate in their study. They asked each participant to perform two auditory cognitive tasks: an executive task modified from the “n-back task”, in which participants had to determine whether their current sound was the same as the one they had heard twice earlier , or if it contained the letter “K”; and an emotional task, in which participants had to identify the gender of a voice spoken in either a neutral tone or an angry tone. Each task was performed while individuals were alternately placed in darkness or exposed to short periods of light at four illumination levels. The team used a technique called 7-Tesla functional magnetic resonance imaging, which offers higher resolution and signal-to-noise ratio than standard 3-Tesla MRI, to assess the impact of different lighting levels on hypothalamus activity during tasks.
They found that, during both tasks, higher light levels triggered increased activity in the posterior hypothalamus. In contrast, the inferior hypothalamus and anterior hypothalamus followed a seemingly opposite pattern, exhibiting reduced activity under higher light levels.
Next, the team sought to determine whether these changes in regional hypothalamus activity were linked to a change in cognitive performance. It focused on assessing participants’ performance during the executive task, as it requires a higher level of cognition. Their analysis found that higher light levels actually led to better performance in the task, indicating an increase in cognitive performance. 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 direct mediator of the positive impact of light on cognitive performance, and this could indicate that other brain regions are involved, which would require further research. more in-depth.
On the other hand, posterior hypothalamus activity was found to be associated with an increased behavioral response to 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.
The authors call for future work in this area to assess the impact of light on other structures, or entire brain networks, to determine how varying light levels alter their dialogue and interactions with the cortex to bring about behavioral changes.
“It is important to answer the questions raised by our study, because acting on 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”says Islay Campbell.
“Our results demonstrate that the human hypothalamus does not respond uniformly to different light levels when engaged in a cognitive challenge”explains the lead author, Gilles Vandewalle, co-director of GIGA-CRC Human Imaging. “Our results indicate that this stimulating impact is mediated, in part, by the posterior hypothalamus. This region is likely to act in conjunction with the decreased activity of the anterior and inferior hypothalamus, as well as with other non-hypothalamic brain structures that regulate wakefulness”.
“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. Our results represent an important step toward this goal, at the level of the hypothalamus”note Islay Campbell.
Reference
https://elifesciences.org/reviewed-preprints/96576
