Biomedical subjects

Jerome Siegel

Publications and source records attributed to Jerome Siegel.

3 recordsLinked to original sources

PubMed2005

Animal behaviour: continuous activity in cetaceans after birth.

All mammals previously studied take maximal rest or sleep after birth, with the amount gradually decreasing as they grow to adulthood, and adult fruitflies and rats die if they are forcibly deprived of sleep. It has therefore been assumed that sleep is necessary for development and serves a vital function in adults. But we show here that, unlike terrestrial mammals, killer-whale and bottlenose-dolphin neonates and their mothers show little or no typical sleep behaviour for the first postpartum month, avoiding obstacles and remaining mobile for 24 hours a day. We find that neonates and their mothers gradually increase the amount of time they spend resting to normal adult levels over a period of several months, but never exceed these levels. Our findings indicate either that sleep behaviour may not have the developmental and life-sustaining functions attributed to it, or that alternative mechanisms may have evolved in cetaceans.

Aging↗

PubMed2004

Brain mechanisms that control sleep and waking.

This review paper presents a brief historical survey of the technological and early research that laid the groundwork for recent advances in sleep-waking research. A major advance in this field occurred shortly after the end of World War II with the discovery of the ascending reticular activating system (ARAS) as the neural source in the brain stem of the waking state. Subsequent research showed that the brain stem activating system produced cortical arousal via two pathways: a dorsal route through the thalamus and a ventral route through the hypothalamus and basal forebrain. The nuclei, pathways, and neurotransmitters that comprise the multiple components of these arousal systems are described. Sleep is now recognized as being composed of two very different states: rapid eye movements (REMs) sleep and non-REM sleep. The major findings on the neural mechanisms that control these two sleep states are presented. This review ends with a discussion of two current views on the function of sleep: to maintain the integrity of the immune system and to enhance memory consolidation.

Animals↗

PubMed2004

Sleep: a functional enigma.

Although continued total sleep deprivation is fatal, the function of sleep remains a mystery. Shorter durations of sleep deprivation are followed by rebound increases in non-rapid eye movement (non-REM) sleep, suggesting a homeostatic control. Measurements of the power spectrum of the electroencephalograph (EEG) suggest that a more accurate marker of the homeostasis may be delta frequency power, because it most closely reflects the duration of the preceding sleep deprivation. Several lines of evidence suggest a link with complex metabolic processes. These include a local homeostatic factor, adenosine, that inhibits neuronal activity in response to increases in the ratio of energy demand to metabolite availability. Other evidence derives from the relationship of circadian genes, NPAS2 and Clock, to metabolism. Additionally, at a systems level, hypocretin/Orexin may coordinate motor activity with feeding. A loss of hypocretin neurons or a mutation of the genes controlling this peptide system can result in the sleep disorder narcolepsy. Finally, evidence for a role of non-REM sleep in developmental central nervous system (CNS) plasticity, as well as learning and memory, is discussed.

Adenosine↗