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J Sleep Med > Volume 18(1); 2021 > Article
J Sleep Med. 2021;18(1):46-54.         doi: https://doi.org/10.13078/jsm.210005
Reduced Flicker Lighting Enhances Theta-Band Phase Synchrony during Working Memory Tasks
Jun-Sang Sunwoo1 , Sanghun Lee2,3 , Ki-Young Jung2,4,5
1Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
2Department of Neurology, Seoul National University Hospital, Seoul, Korea
3Department of Mathematical Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
4Program in Neuroscience, Seoul National University College of Medicine, Seoul, Korea
5Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, Korea
Corresponding Author: Jun-Sang Sunwoo ,Tel: +82-2-2072-4988, Fax: +82-2-2072-2474, Email: jungky@snu.ac.kr
Received: February 5, 2021   Revised: March 10, 2021   Accepted: March 30, 2021   Published online: April 29, 2021
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Objectives: We analyzed theta-band phase synchrony (TBPS) under reduced and ordinary flicker lighting to determine the effect of light flickers on neurocognitive processes.
Methods: Nineteen healthy participants (mean age, 30.4±4.5 years; male, 63.2%) performed the Sternberg working memory tasks with event-related potential recording under reduced and control flicker conditions, respectively. We measured the P300 amplitude during memory retrieval, and for TBPS analysis, we calculated the weighted phase lag index within the P300 time window. Furthermore, we used standardized low-resolution brain electromagnetic tomography (sLORETA) to determine differences in functional cortical source connectivity between the two flicker conditions.
Results: The hit rate (F1,18=0.862, p=0.365), reaction time (F1,18=0.021, p=0.887), and P300 amplitude (F1,18=3.992, p=0.061) did not differ between the two flicker conditions. However, connectivity analysis at the scalp level showed that TBPS under reduced flicker lighting was significantly higher than that under control flicker lighting at higher memory loads (p=0.002). Cortical source imaging with sLORETA confirmed that reduced flicker lighting significantly increased TBPS between the left prefrontal cortex and right hippocampus compared with control flicker lighting (false discovery rate<0.1).
Conclusions: Reduced flicker lighting enhanced TBPS during the working memory task compared with control flicker lighting. Reduced flicker light may improve cognitive functioning by facilitating information transfer within the brain network. Flicker conditions should be considered when optimizing lighting, especially in environments demanding high-level cognitive performance.
Keywords: Functional connectivity | Theta-band phase synchrony | Flicker | Light-emitting diode | sLORETA
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