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Katharina Wulff

WCMM-associated researcher

Brain health - integrating biological rhythms, sleep and daylight

The environment in which humans live represent crucial differences. The brain developed important nuances in preferring different pathways depending on setting and context. Environmental cycles, such as the daily light-dark cycle or the seasonal climate cycle are immensely strong regulators of physiology and behaviour. The brain performs different anticipatory actions prompted by demands from its surrounding environment. For example, electrical light is necessary for us to see in the dark. But it also predisposes our circadian rhythms to a mismatch between the outdoor world and the anticipated sleep period. In addition, it puts our mental health under strain. While daylight during the day appropriately increases heart rate, muscle tone and arousal in a stimulating environment, those also resemble responses elicited by exposure to stress. Healthy emotions are responsive to the environment and a person’s brain could process electrical light as a mismatch between the expected and the actually encountered, which activates stress response, leading to rumination and delayed sleep. Observing and delineating those differences could help explain which brain pathways are differentially activated by daylight and electrical light depending on context and time.


Our lab combines time-based monitoring of spectral irradiances of light with wearable technology for researchers to track adaptive responses to light from sensory to physiological regulation and behavioural output in real time. We currently set-up the Nordic Daylight Research Facility for daylight studies all year-round at high latitude in Västerbotten, where extreme seasonality coincides with low artificial light pollution. This provides ideal conditions to explore daylight qualities as predictors for physiological responsiveness.


The findings will have practical implications, as to re-evaluate indoor lighting designs for their impact on photoreceptor sensitivities and individual wellbeing as well as in refining therapeutic applications for sleep and stress management in emotionally vulnerable groups in the general population.

Katharina Wulff

Nordic Daylight Research Programme