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Newborn primate infants are entrained by low intensity lighting
S A Rivkees1, P L Hofman, J Fortman
1Section of Pediatric Endocrinology, James Whitcomb Riley Hospital, Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202, USA.
Summary
Human infants
Area of Science:
- Neuroscience
- Chronobiology
- Developmental Biology
Background:
- The timing of the human infant circadian system's responsiveness to light is unknown.
- Clinical studies are limited in investigating early light responses in infants.
Purpose of the Study:
- To determine when the human infant circadian system becomes responsive to light.
- To investigate the role of the suprachiasmatic nuclei (SCN) in mediating light responses at birth.
Main Methods:
- Assessed SCN metabolic activity and c-fos mRNA expression in newborn baboons and infants exposed to light.
- Examined photic entrainment of circadian rhythmicity using cycled lighting in infants.
- Conducted phase-response studies to determine optimal light exposure timing.
Main Results:
- Newborn baboons and infants show increased SCN metabolic activity and c-fos mRNA expression in response to bright light, indicating photic responsiveness at birth.
- Low-intensity cycled lighting (200 lux) can entrain circadian rhythmicity in infants.
- Light exposure before activity onset is most effective for shifting circadian phase.
Conclusions:
- The suprachiasmatic nuclei (SCN) are responsive to visually mediated light at birth in primates.
- Infant lighting conditions warrant further consideration for proper circadian system development.