Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA 02115, USA Division of Sleep Medicine, Harvard Medical School, Boston, MA 02115, USA Center for Dynamical Biomarkers and Translational Medicine, National Central University, Chungli 32001, Taiwan, Republic of China
Departamento de Anatomia, Facultad de Medicina, Edificio 'B' 4 Piso, Universidad Nacional Autónoma de México, México 04510, México.
J R Soc Interface. 2014 Jul 6;11(96). doi: 10.1098/rsif.2014.0318.
Motor activity possesses a multiscale regulation that is characterized by fractal activity fluctuations with similar structure across a wide range of timescales spanning minutes to hours. Fractal activity patterns are disturbed in animals after ablating the master circadian pacemaker (suprachiasmatic nucleus, SCN) and in humans with SCN dysfunction as occurs with aging and in dementia, suggesting the crucial role of the circadian system in the multiscale activity regulation. We hypothesized that the normal synchronization between behavioural cycles and the SCN-generated circadian rhythms is required for multiscale activity regulation. To test the hypothesis, we studied activity fluctuations of rats in a simulated shift work protocol that was designed to force animals to be active during the habitual resting phase of the circadian/daily cycle. We found that these animals had gradually decreased mean activity level and reduced 24-h activity rhythm amplitude, indicating disturbed circadian and behavioural cycles. Moreover, these animals had disrupted fractal activity patterns as characterized by more random activity fluctuations at multiple timescales from 4 to 12 h. Intriguingly, these activity disturbances exacerbated when the shift work schedule lasted longer and persisted even in the normal days (without forced activity) following the shift work. The disrupted circadian and fractal patterns resemble those of SCN-lesioned animals and of human patients with dementia, suggesting a detrimental impact of shift work on multiscale activity regulation.
运动活动具有多尺度调节，其特征是分形活动波动具有相似的结构，跨越从分钟到小时的广泛时间尺度。在切除主生物钟起搏器（视交叉上核，SCN）后的动物中以及在因衰老和痴呆而发生 SCN 功能障碍的人类中，分形活动模式受到干扰，这表明生物钟系统在多尺度活动调节中起着关键作用。我们假设行为周期与 SCN 产生的昼夜节律之间的正常同步是多尺度活动调节所必需的。为了验证假设，我们研究了在模拟轮班工作方案中大鼠的活动波动，该方案旨在迫使动物在昼夜/日常周期的习惯性休息阶段活跃。我们发现，这些动物的平均活动水平逐渐降低，24 小时活动节律幅度减小，表明昼夜节律和行为周期受到干扰。此外，这些动物的分形活动模式被打乱，表现为在从 4 到 12 小时的多个时间尺度上活动波动更加随机。有趣的是，当轮班工作时间表持续更长时间时，这些活动干扰会加剧，并在轮班工作后的正常日子（没有强制活动）中持续存在。受干扰的昼夜和分形模式类似于 SCN 损伤动物和痴呆症人类患者的模式，表明轮班工作对多尺度活动调节有不利影响。
