A report by Buhr et al. (2010) proposed that the suprachiasmatic nucleus (SCN) is resistant to phase shifts induced by heat pulses and to entrainment by temperature cycles. These findings are inconsistent with those from studies by other laboratories in which the SCN readily phase shifts in response to heat pulses. I propose that their negative findings are not due to the SCN being temperature insensitive but are based on an explant culture preparation that does not fully express the properties of the SCN that are present in other in vitro preparations.
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http://dx.doi.org/10.1177/0748730411411678 | DOI Listing |
Vitam Horm
January 2025
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina; Centro de Estudios Biomédicos Básicos, Aplicados y Desarrollo (CEBBAD), Universidad Maimónides, Ciudad Autónoma de Buenos Aires, Argentina. Electronic address:
Light is the most reliable environmental cue allowing animals to breed successfully when conditions are optimal. In seasonal breeders, photoperiod (length of daylight) information is sensed by the eyes and transmitted to the suprachiasmatic nucleus, the master clock region located in the hypothalamus. This structure has a 24-h firing rhythm involving a cycle of clock protein synthesis and degradation, and provides the timing to synchronize the synthesis and release of melatonin, the chemical signal that transduces the photoperiod information.
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January 2025
Massachusetts General Hospital, Boston, MA, United States.
Irregular sleep-wake rhythm disorder (ISWRD) is an intrinsic circadian rhythm disorder caused by loss of the brain's circadian regulation, through changes of the input and/or output to the suprachiasmatic nucleus (SCN), or of the SCN itself. Although there are limited prevalence data for this rare disease, ISWRD is associated with neurodegenerative disorders, including the Alzheimer disease (AD) and the Parkinson disease (PD), which will become increasingly prevalent in an aging population. It additionally presents in childhood developmental disorders, psychiatric disorders, and traumatic brain injury (TBI).
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January 2025
Sleep Medicine Center, Department of Neurology, Villa Serena Hospital, Città S. Angelo, Pescara, Italy; Villaserena Research Foundation, Città S. Angelo, Pescara, Italy.
Advanced sleep phase (ASP) is seldom brought to medical attention because many individuals easily adapt to their early chronotype, especially if it emerges before the age of 30 and is present in a first-degree relative. In this case, the disorder is considered familial (FASP) and is mostly discovered coincidentally in the presence of other sleep disorders, mainly obstructive sleep apnea syndrome (OSAS). The prevalence of FASP is currently estimated to be between 0.
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January 2025
Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland; Research Cluster Molecular and Cognitive Neurosciences, University of Basel, Basel, Switzerland; Department of Biomedicine, University of Basel, Basel, Switzerland.
The nonvisual effects of light in humans are mainly conveyed by a subset of retinal ganglion cells that contain the pigment melanopsin which renders them intrinsically photosensitive (= intrinsically photosensitive retinal ganglion cells, ipRGCs). They have direct connections to the main circadian clock in the suprachiasmatic nuclei (SCN) of the hypothalamus and modulate a variety of physiological processes, pineal melatonin secretion, autonomic functions, cognitive processes such as attention, and behavior, including sleep and wakefulness. This is because efferent projections from the SCN reach other hypothalamic nuclei, the pineal gland, thalamus, basal forebrain, and the brainstem.
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January 2025
Institute of Brain Science, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Sleep-wake disorders are recognized as one of the earliest symptoms of Alzheimer disease (AD). Accumulating evidence has highlighted a significant association between sleep-wake disorders and AD pathogenesis, suggesting that sleep-wake modulation could be a promising approach for postponing AD onset. The suprachiasmatic nucleus (SCN) and the pineal hormone melatonin are major central modulating components of the circadian rhythm system.
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