Anyone who suffers from insomnia knows all too well the impatience and dissatisfaction that accompanies sleep deprivation, as you struggle to turn off the light in your head and silence your inner voice.
You long for a button or switch that can instantly reduce all that mental activity.
The idea of a mental mute switch is not as far-fetched as it might seem at first glance.
Most neuroscientists today agree that our alertness exists on some kind of continuum.
It is coordinated by a complex network of brain regions, at the center of which is a tiny bundle of neurons known as the "locus coeruleus", which means "blue dot" in Latin.
That is also its literal description: neurons in locus coeruleus-u The sapphires are colored by the production of a special neurotransmitter, called norepinephrine.
This is also a hint at the function of this blue dot, since norepinephrine controls our physiological and psychological alertness.
For a long time, scientists assumed that the locus coeruleus was dormant during sleep, but it is now becoming clear that it is never completely quiescent, with low levels of intermittent activity that could regulate the depth of our sleep.
A better understanding of this process could help treat disrupted sleep associated with conditions such as anxiety.
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Brain gear shifting system
Locus coeruleus It is located in the brainstem, just above the nape of the neck – and contains about 50.000 cells, a tiny fraction of the 86 billion neurons in the average central nervous system.
Marie Antoinette's physician Felix Vik d'Azir was the first to record its existence in the late 18th century, but for a long time it failed to attract much attention.
That began to change in the 20th century, when it became clear that the blue pigment locus coeruleus plays a key role in signaling in the brain.
Norepinephrine (also known as noradrenaline) increases the chance that a neuron will experience a "peak" of electrical discharge.
When activated, cells in the locus coeruleus forward bundles of this neurotransmitter along their projections to other areas of the brain – thereby enhancing communication between neurons in that given area.
This process is quite complex.
Depending on the type of receptors they have, some neurons are more sensitive to smaller amounts of norepinephrine, while others only respond to higher thresholds.
This means that, as the activity locus coeruleus As it grows, it begins to affect some brain areas more than others, which can have dramatic effects on things like our attention, concentration, and creativity.
In her book "Hyperefficient: Optimize your brain to transform the way you work", neuroscience researcher and writer Mitu Storoni describes locus coeruleus, and its control over norepinephrine signaling, as a gear shifter in the brain, with different modes best suited to certain types of activity.
First speed: very gentle activity in the blue dot. Low levels of norepinephrine mean that our attention is scattered and our brains are wandering from thought to thought.
Second speed: moderate firing in the blue dot, accompanied by occasional spikes in reactions to the most relevant stimuli.
The prefrontal cortex, which is involved in self-control and abstract thinking, is most sensitive to this concentration of norepinephrine.
In this brain state, it might be easiest for us to stay focused on intellectual tasks.
Top gear: a constant high firing in the blue dot, which releases high levels of norepinephrine.
This starts to trigger activity in brain areas associated with the "fight or flight" response, while the prefrontal cortex starts to shut down.
Thanks to increased communication between neurons, you are extremely sensitive to your environment, but it can be difficult to separate signals from noise.
It becomes harder to concentrate and you may start to feel fatigued.
A number of different factors determine what speed we are in, such as the time of day, since the activity of the blue dot changes with our circadian rhythm.
It is usually lowest when we first wake up, rises during the day, and then falls in the evening.
Night vigil
Given the role of the blue dot in awakening, it makes sense that it is calmest at night during sleep.
It is not, however, completely silent, but rather fires sporadically, and recent research by Anita Luti at the University of Lausanne, Switzerland, suggests that this activity may determine the quality of our sleep.
Throughout the night, we alternate between different stages of sleep.
There is a phase of "rapid eye movement" (REM) sleep, which, as its name suggests, is marked by the blinking of our eyeballs.
It is associated with vivid dreams and is thought to be crucial for processing and consolidating our memories.
The bulk of our rest, however, is spent in the non-REM (NREM) stage of sleep, during which the brain may engage in deep cleansing, clearing out cellular waste that could lead to neuronal dysfunction if allowed to accumulate.
Measuring brain activity in sleeping mice, Luti discovered that NREM sleep is associated with temporary bursts of activity locus coeruleus-a every 50 seconds.
This seems to activate the thalamus, a pair of egg-shaped areas located in the middle of the brain that are involved in processing sensory information.
As a result, the animal was more sensitive to external stimuli, such as noise, without fully waking up.
"It generates this state of heightened alertness," says Luti.
"It gives you an idea that alertness can have gradations in the brain."
Luti suggests that these regular periods of heightened vigilance for potential threats were crucial for survival in the wild.
"Sleep is essential, but it must be complemented by a mechanism that allows for a certain level of wakefulness," he says.
"You have to remain somewhat aware of your surroundings."
The onset of REM sleep is almost always associated with low activity. locus coeruleus-a, suggesting that it plays a key role in the shift to this dream-filled state of existence as well.
"This transition into REM sleep has to be very controlled," Luti says, "because in REM sleep we have atonia."
It is a temporary paralysis of our body, which prevents us from physically realizing our dreams.
"We are completely disconnected from our environment."
Luti emphasizes that her experiments were conducted on rodents, so we still need to confirm that the blue dot plays a similar role in human sleep.
If so, she suspects that the altered activity locus coeruleus-a may play a role in anxiety, which can contribute to sleep disturbance.
She found that exposing laboratory mice to mild sources of stress, such as knocking on their cage, increased blue dot activity and increased their alertness during the night, resulting in disrupted sleep.
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Finding mental peace
A greater understanding of this neural pathway is leading some scientists to investigate whether different types of brain stimulation can quiet the blue spot to improve sleep.
A team in South Korea, for example, recently tested a helmet that sends a mild electrical charge through one of the nerves in the forehead associated with the blue dot to temporarily reduce its activity, although it is not yet known whether this reduces insomnia.
For now, we can just think a little more carefully about our behavior in the evening and avoid overstimulation just before going to sleep.
"If you force yourself to keep pushing when you're tired, your brain copes by revving up to provide maximum horsepower for the spinning machinery—so much so that it almost gets stuck in a higher gear," Storoni writes in Hyperefficient.
Simply allowing our brains to unwind before bed - without the TV, phone or tablet - has long been considered good "sleep hygiene".
We could also use two-way traffic between locus coeruleus-a and fabric.
The blue dot is part of the autonomic nervous system, which controls physiological functions such as breathing, heart rate, and blood pressure.
It is divided into two branches: the sympathetic nervous system, responsible for initiating the stress response, and the parasympathetic nervous system, which prepares the body for rest and relaxation.
And it seems that we can selectively activate each branch with different physical activities.
Moderate to vigorous exercise - walking, running, rowing, cycling or boxing - can activate the sympathetic branch, accelerating the activity of the blue dot and enhancing our mental alertness.
That's great news if you're feeling groggy in the morning and need to wake up, but less useful when you're trying to calm your mind after a busy day.
You might think that physical exhaustion will tire you out, but if you already have trouble falling asleep, late-night gym trips are a bad idea.
Gentle stretching, on the other hand, can trigger a relaxation response in the parasympathetic nervous system that simultaneously calms our thoughts and feelings.
Controlled breathing exercises, such as pranayama - an ancient breathing technique that originated in yoga practice - seem to achieve the same effect, with slower breathing rhythms that reduce overall alertness.
We can turn this to our advantage as we relax before bed.
Various tests have shown that meditation and mindfulness movements can reduce the time it takes to fall asleep and improve our overall sleep quality, better than standard treatment for insomnia.
We don't really have a physical switch that can turn off our mental activity whenever we want.
But by managing our daily routine, however, and utilizing our mind-body connection, we will have a better chance of getting the deep rest we so desperately need.
* David Robson is an award-winning science journalist and author. His latest book is "The Laws of Connection: 13 Social Strategies That Will Transform Your Life." He is @davidarobson on Instagram and Threads and writes the Psychology in 60 Seconds newsletter on Substech.
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