Simulated shift work in rats perturbs multiscale regulation of locomotor activity.
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.
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 hsieh1979@gmail.com.
Wan-Hsin
WH
Hsieh
Departamento de Anatomia, Facultad de Medicina, Edificio 'B' 4 Piso, Universidad Nacional Autónoma de México, México 04510, México.
Carolina
C
Escobar
Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA 02115, USA Medical Chronobiology 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.
Tatiana
T
Yugay
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.
Men-Tzung
MT
Lo
Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA 02115, USA Medical Chronobiology 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.
Benjamin
B
Pittman-Polletta
Laboratorio de Biología Celular Fisiología, Facultad de Ciencias, Universidad Autónoma de San Luis Potosí, San Luis Potosí 78290, México.
Roberto
R
Salgado-Delgado
Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA 02115, USA Medical Chronobiology 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.
Frank A J L
FA
Scheer
Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA 02115, USA Medical Chronobiology 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 Research on Occupational and Environmental Toxicology, Oregon Health and Science University, Portland, OR 97239, USA.
Steven A
SA
Shea
Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México 04510, México.
Ruud M
RM
Buijs
Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA 02115, USA Medical Chronobiology 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 khu@bics.bwh.harvard.edu.
Kun
K
Hu
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D009043:Motor Activity; D017440:Photoperiod; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000502:physiology; D014940:Work Schedule Tolerance / Q000502:physiology
circadian misalignment; multiscale regulation; shift work