Insulin signaling shapes fractal scaling of C. elegans behavior

Abstract

AbstractFractal 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 culturedC. elegansin a microfluidic device for 3 days and analyzed temporal patterns ofC. elegansactivity by fractal analyses. The residence-time distribution ofC. elegansbehaviors 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-defectivedaf-2anddaf-16mutants. 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 indaf-2anddaf-16mutants. We conclude that insulin signaling differentially affects mechanisms that determine the residence time in active and inactive states inC. elegansbehavior. 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.