Bergen Stress and Sleep Group, BSSG

Sleep dynamics in rats after exposure to long or short photoperiod

Collage av hjernebølger, døgnrytmefigur med endring i lysintensitet gjennom døgnet og bilde av rotte i rom med blått lys

From the beginning of the earth’s rotation, predictable changes in the light environment have enabled organisms to confine their rest-activity rhythms and physiology to specific and adaptive times of the light-dark cycle. Light resets our biological clock to the 24 hours rhythm, and regulates when we are asleep and when we are awake.

With the introduction of electric light and the evolution of our fast-pacing 24-hour society, modern humans expose themselves to more artificial light (such as that from LED devices) and less natural light. The hours of light and dark across the 24 hours is often referred to as the ‘photoperiod’. Changing the photoperiod, e.g. by extending the hours of light in a day, may lead to long-term changes in circadian rhythmicity and sleep.

This project aims to assess the effects of exposure to and recovery from a long (20 hours light, 4 hours dark) or a short (4 hours light, 20 hours dark) photoperiod on wakefulness, sleep, EEG markers of sleep consolidation and molecular markers of brain function and protein synthesis in rats.  Additionally, the project aims to characterize the differential effects of white vs. blue-enriched light in the two various photoperiod conditions.

Sleep in rats is scored based upon information from brain activity (EEG) and muscle tonus (EMG). Scoring sleep in rats is highly time and resource demanding, motivating the development and improvement of algorithms that can classify sleep and wake states on their own. In collaboration with Washington State University, this project involves the validation of a semi-automatic algorithm for sleep state classification in the rat, and the development and use of a detailed app for EEG analysis.


Master degrees

Louise Haugen Bjerrum. Sleep-wake dynamics and EEG in a rat model of Prolonged Photoperiod

Jorrit Waslander. Effects of prolonged light exposure on clock genes, plasticity, and activity in the brain