There are countless adverse health effects associated with not getting enough sleep. But a recent study may pave the way for new sleep therapies, as a single brain area is found to control both sleep and wakefulness.
From raising the risk of both hypertension and obesity to making depression and cancer more likely, sleep deprivation can harm our immune system just as much as our mental well-being. A survey carried out by the Centers for Disease Control and Prevention (CDC) revealed that 50 to 70 million adults in the United States have chronic sleep disorders. They also found that over 35 percent of them do not get the minimum 7 hours that an adult needs for optimal health. This prompted the CDC to deem sleep deprivation a “public health epidemic,” urging researchers to come up with new sleep therapies and unlock the mystery of how our brain induces the restful state. Until now, it was believed that our brain uses several regions to alternate between sleep and wakefulness. For instance, a popular hypothesis maintains that the cerebral cortex — that is, the upper part of the brain that can be found right beneath the skull — “emits” sleep-inducing slow brain waves, whereas wakefulness is controlled by the lower, mammalian part of our brain. New research has turned this hypothesis on its head. Scientists from the Department of BioMedical Research at the University of Bern and the Department of Neurology at Inselspital, Bern University Hospital — both in Switzerland — find neurons that control both sleep and wakefulness. The team was led by senior author Prof. Antoine Adamantidis, of the Department of Neurology at Inselspital. Thomas Gent, a researcher in the same department, is the first author of the paper. The findings, which may pave the way for new sleep therapies, were published in the journal Nature Neuroscience. Prof. Adamantidis and team used optogenetics to selectively switch neurons on and off in mice’s brains. Optogenetics is a technique in which neurons are genetically modified to respond to light. In this case, the scientists modified neurons in the rodents’ thalamus, or the brain area responsible for relaying sensory information to the cortex. The thalamus is also involved in mood regulation and states of arousal, or consciousness. In this study, the researchers used prolonged stimuli to activate these neurons, which woke up the rodents. However, using slow stimuli in a rhythmic way induced a deep, non-rapid eye movement (REM) sleep in the mice, as measured by an electroencephalogram. REM and non-REM sleep are the two main sleep phases; the former is the stage during which we dream, while the latter is the deep, restorative sleep. To the authors’ knowledge, this was the first time that a study has revealed that a single brain area promotes both sleep and wakefulness. “Interestingly,” explains Gent, “we were also able to show that suppression of thalamic neuronal activity impaired the recovery from sleep loss, suggesting that these neurons are essential for a restful sleep after [an] extended period of being awake.” The study’s senior author also weighs in on the clinical significance of the findings.
 Until now, it was thought that multiple brain areas were needed to control sleep and wakefulness. Neuroscientists from Bern have now identified one single control center for the sleep-wake cycle in the brain. The findings are of great importance for finding new sleep therapies. Every night we spend several hours asleep and every morning we awaken to go about our lives. How brain circuits control this sleep-wake cycle remains a mystery. Our sleep is divided into two phases, non-rapid eye movement (NREM) sleep, and REM (or paradoxical) sleep during which most of our dreaming occurs. Important brain circuits have been identified using both experimental and clinical evidence, yet the precise underlying mechanisms, such as the onset, maintenance and termination of sleep and dreaming, is not well understood. When we fall asleep, the electroencephalogram (EEG) reveals that our brains generate rhythmic oscillations called "slow waves". These waves are important for keeping us asleep and for recovering after a full day of mental and physical activity. Common hypotheses hold that these slow waves are produced in the cerebral cortex, the upper part of the brain just below the surface of the skull. In contrast, wakefulness was thought to arise from the activity of "wake centers" located in the lower part of the brain including the brainstem that directly activates the neocortex, which is the part of the mammalian brain involved in higher-order brain functions such as sensory perception, cognition and generation of motor commands. In an important new study, neuroscientists at the Department of BioMedical Research (DBMR) at the University of Bern and the Department of Neurology at Inselspital, Bern University Hospital, found that neurons in the thalamus, a central hub of the brain, control sleep as well as wakefulness. The thalamus is connected to almost all other brain areas and supports important brain functions including attention, sensory perception, cognition and consciousness. Switching sleep on and offThe researchers headed by Prof. Dr. Antoine Adamantidis discovered that a small population of these thalamic neurons have a dual control over sleep and wakefulness, by generating sleep slow waves but also waking up from sleep, depending on their electrical activity. The research group used a technique called optogenetics, with which they used light pulses to precisely control the activity of thalamic neurons of mice. When they activated thalamic neurons with regular long-lasting stimuli the animals woke up, but if they activated them in a slow rhythmical manner, the mice had a deeper, more restful sleep. This is the first time that an area of the brain has been found to have both sleep and wake promoting functions. "Interestingly, we were also able to show that suppression of thalamic neuronal activity impaired the recovery from sleep loss, suggesting that these neurons are essential for a restful sleep after extended period of being awake", says Dr. Thomas Gent, lead author of the study. This shows that the thalamus is a key player in both sleep and wake. The study has now been published in the journal Nature Neuroscience. Breakthrough for sleep medicineThe findings of this study are particularly important in a modern world, where the active population sleeps about 20 % less than 50 years ago and suffers from chronic sleep disturbances. People frequently work irregular hours and rarely catch up on lost sleep. Poor sleep is increasingly linked to a multitude of psychiatric diseases and weakens the immune system. "We believe that uncovering the control mechanisms of thalamic neurons during sleep and wake will be key to finding new sleep therapies in an increasingly sleep deprived society", says Prof. Antoine Adamantidis. This article has been republished from materials provided by Universitat Bern. Note: material may have been edited for length and content. For further information, please contact the cited source. Reference: |
Part of the brain that controls sleep
Copyright © 2024 hanghieugiatot Inc.
