Brain Activity During Sleep
Understanding the activity of different parts of the brain during sleep can give a clue to the functions of sleep. It has been observed that mental activity is present during all stages of sleep, though from different regions in the brain. So, contrary to popular understanding, the brain never completely shuts down during sleep. Also, sleep intensity of a particular region is homeostatically related to the corresponding amount of activity before sleeping. The use of imaging modalities like PET and fMRI, combined with EEG recordings, gives a clue to which brain regions participate in creating the characteristic wave signals and what their functions might be.
Is A Circadian Rhythm The Same As A Biological Clock
Biological clocks help regulate the timing of bodily processes, including circadian rhythms. A circadian rhythm is an effect of a biological clock, but not all biological clocks are circadian. For instance, plants adjust to changing seasons using a biological clock with timing that is distinct from a 24-hour cycle.
What Are Good Sleep Habits
Good sleep habits, also called good sleep hygiene, are practices to help you get enough quality sleep.
- Have a sleep schedule: Go to sleep and wake up around the same time every day, even on weekends and vacations.
- Clear your mind before bed: Make a to-do list early in the evening, so you wont stay awake in bed and worry about the next day.
- Create a good sleep environment: Make sure your bed and pillows are comfortable. Turn down the lights and avoid loud sounds. Keep the room at a comfortable temperature.
- Exercise every day: Stay active but try to avoid exercising during the few hours right before bed.
- Relax: Before bed, take a warm bath, read or do another relaxing activity.
- See your healthcare provider: If youve been having trouble sleeping or feel extra drowsy during the day, talk to your provider. There are many treatments available for sleep disorders.
A note from Cleveland Clinic
Far from being a state of doing nothing, sleep is an essential part of our lives. It helps our body rest, recharge and repair. There are four sleep stages three in the non-REM phase plus REM sleep. Many factors can affect sleep quality, including the food and drink you consume before bed and room temperature. Many people experience trouble sleeping now and then. But if you think you may have a sleep disorder, talk to your healthcare provider. Common sleep disorders include insomnia and sleep apnea . Your provider can help you get the diagnosis and treatment you need.
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What Happens Neurologically That Causes Us To Wake Up From Sleep
This is actually a very complex question.There are at least 12 neurotransmitters and hormones that play intimate roles in the sleep-wake cycle. I will go through a list of all of them and talk a little bit about what they do. There has been so much research done on this area and so many mechanisms and interactions have been found that it would be almost impossible to pull everything together in this answer. I will try to give a quick summary and some links to papers in relation to each neurotransmitter and hormone.
Brain Chemicals And Sleep
Chemicals called neurotransmitters send messages to different nerve cells in the brain. Nerve cells in the brainstem release neurotransmitters. These include norepinephrine, histamine, and serotonin. Neurotransmitters act on parts of the brain to keep it alert and working well while you are awake.
Other nerve cells stop the messages that tell you to stay awake. This causes you to feel sleepy. One chemical involved in that process is called adenosine. Caffeine promotes wakefulness by blocking the receptors to adenosine. Adenosine seems to work by slowly building up in your blood when you are awake. This makes you drowsy. While you sleep, the chemical slowly dissipates.
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How The Brain Controls Sleep
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Sleep is usually considered an all-or-nothing state: The brain is either entirely awake or entirely asleep. However, MIT neuroscientists have discovered a brain circuit that can trigger small regions of the brain to fall asleep or become less alert, while the rest of the brain remains awake.
This circuit originates in a brain structure known as the thalamic reticular nucleus , which relays signals to the thalamus and then the brains cortex, inducing pockets of the slow, oscillating brain waves characteristic of deep sleep. Slow oscillations also occur during coma and general anesthesia, and are associated with decreased arousal. With enough TRN activity, these waves can take over the entire brain.
The researchers believe the TRN may help the brain consolidate new memories by coordinating slow waves between different parts of the brain, allowing them to share information more easily.
Natural sleep and general anesthesia
Box 3lesion Studies Of Dreaming
The primary source on neuropsychology of dreaming is a study by Solms who examined 361 neurological patients and asked them in detail about their dreaming. Overall, lesion studies indicate that dreaming depends on specific forebrain regions rather than on the brainstem REM sleep generator. In most cases, global cessation of dreaming follows damage in or near the temporo-parieto-occipital junction , more often unilaterally than bilaterally. This region supports various cognitive processes that are essential for mental imagery. Accordingly, patients with such damage typically show a parallel decline in waking visuo-spatial abilities. These results strongly suggest that mental imagery is the cognitive ability most related to dreaming .
Apart from global cessation of dreaming, more restricted lesions produce the cessation of visual dreaming , or the disruption of particular visual dimensions in dreams. For example, lesions in specific regions that underlie visual perception of color or motion are associated with corresponding deficits in dreaming. In general, it seems that lesions leading to impairments in waking have parallel deficits in dreaming.
Despite these remarkable similarities, what makes dream consciousness so fascinating are the ways in which it differs from our waking experience. Some of these phenomenological differences are accompanied by consistent neurophysiological differences.
Reduced voluntary control and volition
Altered mnemonic processes
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Single Area Of The Brain Wakes You Up And Puts You To Sleep
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Ontogeny And Phylogeny Of Sleep
The questions of how sleep evolved in the animal kingdom and how it developed in humans are especially important because they might provide a clue to the functions and mechanisms of sleep respectively.
The evolution of different types of sleep patterns is influenced by a number of selective pressures, including body size, relative metabolic rate, predation, type and location of food sources, and immune function. Sleep is tricky behavior because it steeply increases predation risk. This means that, for sleep to have evolved, the functions of sleep should have provided a substantial advantage over the risk it entails. In fact, studying sleep in different organisms shows how they have balanced this risk by evolving partial sleep mechanisms or by having protective habitats. Thus, studying the evolution of sleep might give a clue not only to the developmental aspects and mechanisms, but also to an adaptive justification for sleep.
One challenge studying sleep evolution is that adequate sleep information is known only for two phyla of animals- chordata and arthropoda. With the available data, comparative studies have been used to determine how sleep might have evolved. One question that scientists try to answer through these studies is whether sleep evolved only once or multiple times. To understand this, they look at sleep patterns in different classes of animals whose evolutionary histories are fairly well-known and study their similarities and differences.
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Thalamic Neurons Drive Sleep
Prof. Adamantidis and team used optogenetics to selectively switch neurons on and off in mices 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 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 extended period of being awake.
The studys senior author also weighs in on the clinical significance of the findings.
Dhomeostatic And Circadian Sleep Regulation
The sleep/wake cycle is not solely under circadian control. Homeostatic regulatory mechanisms pose another important influence on sleep-propensity. Sleep propensity clearly builds up when the time spent awake increases. Furthermore, an extended period of wakefulness is followed by a compensatory increase of sleep afterward. Several experimental paradigms have been developed to disentangle the circadian and homeostatic contributions to sleep regulation. Examples include constant routine studies in which the influence of environmental and behavioral factors are kept as constant as possible over the experimental period, so that the 24-hour variation measured in a variable can be attributed mainly to the endogenous pacemaker. Forced desynchrony studies use a sleep/wake schedule with a period clearly different from 24 hours that is forced upon the subjects, under constant dim-light conditions that do not entrain the circadian pacemaker. In this paradigm there is an increasing loss of synchronization between the rhythms imposed by the circadian pacemaker and the artificially induced sleep/wake cycle. This makes it possible to determine the influence of both circadian and homeostatic processes on a certain variable under study.
W.R. Pigeon, M.A. Grandner, in, 2013
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Box 1can Reports Be Trusted To Accurately Convey Internal Experiences In Sleep
Do dream reports obtained by awakening a sleeping subject accurately convey subjective experiences in sleep? At one extreme, we could be fully conscious throughout sleep but remember dreams well, little, or not at all depending on the brain state when we are awakened. Indeed, we know that dreaming often goes unreported some people claim they rarely dream, but systematic awakenings in sleep labs have revealed that we greatly underestimate how often and how much we are conscious during sleep. On the other hand, neurological patients who report loss of dreaming are no more likely to have memory disorders than those who report dreaming, suggesting that lack of dream reports indeed reflects lack of experience rather than changes in memory alone. Further studies may illuminate this issue since, for example, memory-related regions in the medial temporal lobe are highly active in REM sleep .
Functional neuroanatomy of human REM sleep: a meta-analysis of PET results
Blood Supply To The Brain
Two sets of blood vessels supply blood and oxygen to the brain: the vertebral arteries and the carotid arteries.
The external carotid arteries extend up the sides of your neck, and are where you can feel your pulse when you touch the area with your fingertips. The internal carotid arteries branch into the skull and circulate blood to the front part of the brain.
The vertebral arteries follow the spinal column into the skull, where they join together at the brainstem and form the basilar artery, which supplies blood to the rear portions of the brain.
The circle of Willis, a loop of blood vessels near the bottom of the brain that connects major arteries, circulates blood from the front of the brain to the back and helps the arterial systems communicate with one another.
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Benefits Of Good Sleep
Having a good mattress can be a key component to sleeping well. Getting a regular and good amount of sleep each night can be very beneficial. 7-9 hours of sleep nightly can be rewarding for your health.
Memory Being able to remember and learn is affected by the amount of sleep you obtain. While you are sleeping, your brain is processing all of the information that you learned during that day. It processes and stores this information. If you arent getting the amount of sleep needed, your brain cant process this information correctly and your memory will suffer because of it.
Mood A study showed that individuals who received less than 4.5 hours of sleep reported feeling sad, angry, and mentally exhausted. Getting the sleep that your body needs allows you to have a better control over your emotions and impulses.
Skin While sleeping, your body produces collagen. With a lack of collagen, occurring during sleepless nights, you are likely to notice an increase in wrinkles and fine lines.
Stress When you are stressed, its often hard to fall and stay asleep. But, this can even cause more stress the next day and even a harder time falling asleep . Managing your stress can significantly help your sleep patterns.
Weight Control This one may be very surprising. Individuals who sleep well every night have an ability to lose 50% more fat than those who arent well rested. This is because your metabolism doesnt function correctly if you arent getting a proper nights sleep.
Effects On The Hypothalamus
Narcolepsy develops as a result of changes in the hypothalamus region of your brain. This small gland is located above your brain stem.
The hypothalamus helps regulate the release of hormones that affect numerous parts of your body. For example, its responsible for releasing hypocretins, which help regulate sleep.
Aside from regulating your sleep cycles, the hypothalamus also plays a role in the following processes:
- heart rate
A rare form of narcolepsy can develop as a result of damage to the hypothalamus from a brain injury. This is known as secondary narcolepsy.
Secondary narcolepsy is a severe neurological condition that can lead to irregular sleep cycles as well as memory loss and mood disorders.
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Renormalizing The Synaptic Strength
Sleep can also serve to weaken synaptic connections that were acquired over the course of the day but which are not essential to optimal functioning. In doing so, the resource demands can be lessened, since the upkeep and strengthening of synaptic connections constitutes a large portion of energy consumption by the brain and tax other cellular mechanisms such as protein synthesis for new channels. Without a mechanism like this taking place during sleep, the metabolic needs of the brain would increase over repeated exposure to daily synaptic strengthening, up to a point where the strains become excessive or untenable.
When To See A Doctor
Everyone experiences a headache from time to time. But, according to the Mayo Clinic, you should see a doctor if your headaches:
You should seek emergency care if you ever have a headache alongside:
- Confusion or trouble understanding speech
- High fever, greater than 102 F to 104 F
- Numbness, weakness or paralysis on one side of your body
- Stiff neck
- Nausea or vomiting
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What Your Brain Does While You Sleep
- Sleep Stage 1: As you enter this first stage of sleep, your brain slowly changes from wakefulness to sleep. If there is a change in your surroundings, you are likely to wake up.
- Sleep Stage 2: Your heart rate and brain waves slow during stage 2 sleep, preparing your mind and body for restorative deep sleep.
- Sleep Stage 3: During stage 3 sleep, your brain waves reach their lowest frequency, and it would be hard for anything to disturb your slumber. As a result, stage 3 sleep is also known as slow wave sleep or deep sleep. How much deep sleep you get will dictate how well-rested you feel come morning.
- REM Sleep: Finally, you reach the final stage of sleep: rapid eye movement sleep . Your brain is the most active that it will be as you sleep. According to the National Institutes of Health, most of your dreams will occur now as your body is temporarily paralyzed. This sleep stage is pivotal for your memory and learning potential.
This cycle will take around 90 minutes. After you complete your first cycle, it will start over again.