title: Interactive Effects of Dorsomedial Hypothalamic Nucleus and Time-Restricted Feeding on Fractal Motor Activity Regulation.
abstract: One evolutionary adaptation in motor activity control of animals is the anticipation of food that drives foraging under natural conditions and is mimicked in laboratory with daily scheduled food availability. Food anticipation is characterized by increased activity a few hours before the feeding period. Here we report that 2-h food availability during the normal inactive phase of rats not only increases activity levels before the feeding period but also alters the temporal organization of motor activity fluctuations over a wide range of time scales from minutes up to 24 h. We demonstrate this multiscale alteration by assessing fractal patterns in motor activity fluctuations-similar fluctuation structure at different time scales-that are robust in intact animals with ad libitum food access but are disrupted under food restriction. In addition, we show that fractal activity patterns in rats with ad libitum food access are also perturbed by lesion of the dorsomedial hypothalamic (DMH)-a neural node that is involved in food anticipatory behavior. Instead of further disrupting fractal regulation, food restriction restores the disrupted fractal patterns in these animals after the DMH lesion despite the persistence of the 24-h rhythms. This compensatory effect of food restriction is more clearly pronounced in the same animals after the additional lesion of the suprachiasmatic nucleus (SCN)-the central master clock in the circadian system that generates and orchestrates circadian rhythms in behavior and physiological functions in synchrony with day-night cycles. Moreover, all observed influences of food restriction persist even when data during the food anticipatory and feeding period are excluded. These results indicate that food restriction impacts dynamics of motor activity at different time scales across the entire circadian/daily cycle, which is likely caused by the competition between the food-induced time cue and the light-entrained circadian rhythm of the SCN. The differential impacts of food restriction on fractal activity control in intact and DMH-lesioned animals suggest that the DMH plays a crucial role in integrating these different time cues to the circadian network for multiscale regulation of motor activity.
authors.affiliation: Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Harvard Medical SchoolBoston, MA, USA; Institute of Translational and Interdisciplinary Medicine and Department of Biomedical Sciences and Engineering, National Central UniversityTaoyuan, Taiwan.
authors.forename: Men-Tzung
authors.initials: MT
authors.lastname: Lo
authors.affiliation: Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA.
authors.forename: Wei-Yin
authors.initials: WY
authors.lastname: Chiang
authors.affiliation: Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA.
authors.forename: Wan-Hsin
authors.initials: WH
authors.lastname: Hsieh
authors.affiliation: Departamento de Anatomía, Facultad de Medicina, Edificio "B" 4° Piso, Universidad Nacional Autónoma de México México, Mexico.
authors.forename: Carolina
authors.initials: C
authors.lastname: Escobar
authors.affiliation: Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México México, Mexico.
authors.forename: Ruud M
authors.initials: RM
authors.lastname: Buijs
authors.affiliation: Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Hu
keywords: circadian rhythm; dorsomedial hypothalamic nucleus; food anticipation; fractal regulation; motor activity; suprachiasmatic nucleus