Yi-Sheng Chen², Hung-Wei Chen², Yu-Sheng Chen¹, Ya-Chuan Huang¹, Chien-Ming Yang¹, and Chien-Yu Chen²*
¹ Department of Psychology, National Chengchi University, Taipei, Taiwan.
² Graduate Institute of Color and Illumination Technology, National Taiwan University of Science and Technology, Taipei, Taiwan
*Corresponding author: Chien-Yu Chen, chencyue@mail.ntust.edu.tw
Poster Presentation Video: https://youtu.be/w_H5dxBGGXs
Light is an effective stimulator that regulates body's circadian rhythms, hormones, and behavior. According to our team's previous researches, dynamic light is very effective in improving circadian rhythm disorders, promoting sleep efficiency, and improving work efficiency. This study further explored the effect of dynamic light on sleep and memory by comparing different lighting conditions during a nap. This experiment recruited 14 volunteers with an average age of 23.3 years. Each volunteer underwent three afternoon nap tests with polysomnographic recording, including EEG (Electroencephalography, EEG) and ECG (Electrocardiography, ECG). The first nap test was to allow the volunteers to adapt to the sleeping environment in the lab. The second and third nap tests were to compare the sleep under two lighting environments: a dynamic color temperature and a fixed color temperature lighting. Questionnaires were administered to measure the degree of sleepiness and emotional state of the volunteers before and after each nap. A word-pair memory test was also conducted to assess the memory consolidation during the nap under two different light sources.
The study hypothesized that dynamic color temperature can increase sleep slow wave activity (SWA), parasympathetic nerve system (vagal tone), and promote memory consolidation, emotion regulation during afternoon sleep, as well as to reduce fatigue. The experimental results show that dynamic color temperature lighting is better than fixed color temperature in increasing total sleep time. It was shown that in the dynamic light had significantly increased slow wave activity in C3, C4 and F4 (frontal lobe and parietal lobe area) . However, there is no significant difference in rating of sleepiness, and performance on word-pair memory test and psychomotor vigilance task.
Keywords: Dynamic light1, Slow wave activity (SWA)2, Memory consolidation3, Emotion regulation4, High frequency-heart rate variability (HF-HRV)5.
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