Complex behaviors of various animal species including human are governed by fractal scaling. Fractal scaling of human behaviors is altered by neurodegenerative diseases and aging. However, the mechanism underlying fractal scaling remains unknown. Here, we videorecorded C. elegans cultured in a microfluidic device for 3 days and analyzed temporal patterns of the behaviors by fractal analyses. Residence time distribution in C. elegans behaviors showed a common feature with those of human and mice, i.e., power law distribution for actively-moving state changed to exponential-like decline at longer time scale, whereas that for inactive state did not. We found that the exponential-like decline disappeared in starved C. elegans, and it was restored by culturing animals with glucose. Additionally, the exponential-like decline disappeared in insulin signaling mutants, daf-2 and daf-16. Therefore, we conclude that insulin signaling regulates fractal scaling of C. elegans behavior. Our finding indicates that neurosensory modulation of C. elegans behaviors by insulin signaling is achieved by regulation of fractal scaling. Diabetes mellitus in human is known to be associated with depression, bipolar disorder, and anxiety disorder, which affect daily behavioral activity. Behavioral defects in diabetes patients may be attributed to altered fractal scaling of human behaviors.
Arata Y, Shiga I, Ikeda Y, Jurica P, Kimura H, Kiyono K, Sako Y. Insulin signaling shapes fractal scaling of C. elegans behavior. Sci Rep. 2022 Jun 21;12(1):10481. doi: 10.1038/s41598-022-13022-6. PMID: 35729173; PMCID: PMC9213454.
Yukinobu Arata, Itsuki Shiga, Yusaku Ikeda, Peter Jurica, Hiroshi Kimura, Ken Kiyono, Yasushi Sako (2022) Insulin signaling shapes fractal scaling of C. elegans behavior., Scientific reports, Volume 12, Number 1, pp. 10481
Published in 2022 Jun 21 (Electronic publication in June 21, 2022, midnight )
(Abstract) Fractal scaling in animal behavioral activity, where similar temporal patterns appear repeatedly over a series of magnifications among time scales, governs the complex behavior of various animal species and, in humans, can be altered by neurodegenerative diseases and aging. However, the mechanism underlying fractal scaling remains unknown. Here, we cultured C. elegans in a microfluidic device for 3 days and analyzed temporal patterns of C. elegans activity by fractal analyses. The residence-time distribution of C. elegans behaviors shared a common feature with those of human and mice. Specifically, the residence-time power-law distribution of the active state changed to an exponential-like decline at a longer time scale, whereas the inactive state followed a power-law distribution. An exponential-like decline appeared with nutrient supply in wild-type animals, whereas this decline disappeared in insulin-signaling-defective daf-2 and daf-16 mutants. The absolute value of the power-law exponent of the inactive state distribution increased with nutrient supply in wild-type animals, whereas the value decreased in daf-2 and daf-16 mutants. We conclude that insulin signaling differentially affects mechanisms that determine the residence time in active and inactive states in C. elegans behavior. In humans, diabetes mellitus, which is caused by defects in insulin signaling, is associated with mood disorders that affect daily behavioral activities. We hypothesize that comorbid behavioral defects in patients with diabetes may be attributed to altered fractal scaling of human behavior.(MeSH Terms)