Lo Men-Tzung, Chiang Wei-Yin, Hsieh Wan-Hsin, Escobar Carolina, Buijs Ruud M, Hu Kun
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.
Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA.
Front Physiol. 2016 May 18;7:174. doi: 10.3389/fphys.2016.00174. eCollection 2016.
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.
动物运动活动控制中的一种进化适应是对食物的预期，这种预期在自然条件下驱动觅食行为，并且在实验室中通过每日定时供应食物来模拟。食物预期的特征是在喂食期前几个小时活动增加。在此，我们报告，在大鼠正常的不活跃期给予2小时的食物供应，不仅会增加喂食期前的活动水平，还会在从分钟到24小时的广泛时间尺度上改变运动活动波动的时间组织。我们通过评估运动活动波动中的分形模式来证明这种多尺度改变，即在不同时间尺度上具有相似波动结构，这种结构在自由进食的完整动物中很稳健，但在食物限制条件下会被破坏。此外，我们表明，自由进食的大鼠的分形活动模式也会因下丘脑背内侧核（DMH）损伤而受到干扰，DMH是一个参与食物预期行为的神经节点。食物限制并没有进一步破坏分形调节，而是在DMH损伤后的这些动物中恢复了被破坏的分形模式，尽管24小时节律仍然存在。在视交叉上核（SCN）额外损伤后，这种食物限制的补偿作用在相同动物中更为明显，SCN是昼夜节律系统中的中央主时钟，它与昼夜周期同步产生并协调行为和生理功能中的昼夜节律。此外，即使排除食物预期期和喂食期的数据，食物限制的所有观察到的影响仍然存在。这些结果表明，食物限制会影响整个昼夜/日周期不同时间尺度上的运动活动动态，这可能是由食物诱导的时间线索与SCN的光驱动昼夜节律之间的竞争引起的。食物限制对完整动物和DMH损伤动物的分形活动控制的不同影响表明，DMH在将这些不同的时间线索整合到昼夜网络中以对运动活动进行多尺度调节方面起着关键作用。
