How light and darkness control our biological rhythms

Content

• 1 Alpha rhythm 1.1 General characteristics.

Alpha rhythm

Alpha rhythm (α-rhythm) - oscillation frequency varies from 8 to 13 Hz. The amplitude is 5-100 µV, the highest amplitude occurs with closed eyes and in a darkened room. It is recorded mainly in the occipital and parietal areas (visual parts of the brain).

General characteristics.

It is registered in 85-95% of healthy adults. The alpha rhythm is associated with a relaxed state of wakefulness and rest. Alpha waves occur when we close our eyes and begin to relax.

Alpha rhythm depression

(deficiency of alpha waves) occurs when a person opens his eyes or thinks about a task that requires certain visual representations. With an increase in the functional activity of the brain, the amplitude of the alpha rhythm decreases until it disappears completely. It can also be a sign of anxiety, anger, fear, anxiety, causing depression; disorders associated, to one degree or another, with changes in the activity of the activating systems of the brain and, as a consequence, with an increased level of activation of the autonomic and central nervous systems.

Where is the clock hidden?

The biological clock is one of the body's systems, like the immune or cardiovascular.
All living things need these clocks to synchronize with the rhythms of nature - to adjust to the cycle of day and night or the changing seasons. Many body functions are controlled by the biological clock, including heat regulation, blood pressure, and hormone production. The clock that controls our body operates on three levels. The first is a tiny clock mechanism hidden in every cell. For its discovery, American researchers Jeffrey Hall, Michael Rosbash and Michael Young received the 2021 Nobel Prize in Physiology or Medicine.

The main role in it is played by special clock proteins, which are synthesized in all cells that have a nucleus - in animals, plants, and fungi. Some clock proteins are formed in the morning, activating metabolism in the cell, while others are formed in the evening, inhibiting metabolism. This is how the daily, or circadian (from the Latin circa - around and dies - day), the rhythm of the work of an individual cell is set. And if one of the genes that synthesize clock proteins mutates, various rhythms of the body may be disrupted: sleep and wakefulness, motor activity, and digestion. All these rhythms are connected - if a person does not sleep at night, this can lead not only to insomnia or depression, but also to diabetes, even to cancer.

A clock is needed not only for every cell, but also for the body as a whole. The rhythms of all cells are synchronized by a special hormonal gland in the brain called the pineal gland, or pineal gland, which produces melatonin and serotonin - hormones that regulate our sleep and wakefulness, as well as appetite and mood. During daylight hours, the pineal gland produces the “happiness hormone” serotonin, and during dark hours, serotonin is converted into the “sleep hormone” melatonin - it makes sleep deeper and more complete.

Melatonin is produced in sufficient quantities only in the dark; even dim light reduces its production - turn off all lamps and curtain the windows! Serotonin, on the contrary, needs light: the more light, the better the mood and higher performance.

Now let's move on to the third level. The highest control center for all rhythmic functions of the body is the suprachiasmatic nuclei of the hypothalamus. It is this group of nerve cells that receives a direct signal from the retina, which tells the watch whether it is day or night outside. This small area in the diencephalon is the main generator of circadian rhythms; its neurons adapt to external light signals and control the pineal gland.

Beta rhythm

Beta rhythm (β rhythm) - oscillation frequency varies from 14 to 40 Hz. The amplitude of the oscillation is usually up to 20 μV. Normally, it is very weakly expressed and in most cases has an amplitude of 3-7 μV. It is registered in the area of ​​the anterior and central gyri. Spreads to the posterior central and frontal gyri.

General characteristics.

Beta waves are the fastest. The beta rhythm is normally associated with higher cognitive processes and focusing attention, in a normal waking state, when we observe current events with open eyes, or are focused on solving any current problems.

Beta rhythm depression.

The beta rhythm is associated with somatic, sensory and motor cortical mechanisms and produces an extinction response to motor activation or tactile simulation. When performing or even mentally imagining a movement, the beta rhythm disappears in the zone of corresponding activity. An increase in beta rhythm is an acute reaction to stress.

Using brain waves, scientists determine how neurons juggle possible futures.

Decisions, decisions. We are all constantly forced to make conscious or unconscious choices. Not only when we're thinking about what to wear, what to eat, or how to spend the weekend, but also when we're deciding which hand to pick up a pencil or whether to distribute our weight differently when sitting in a chair. Even with a trivial choice, our brain goes through a bunch of “What if?” options. and weighs them. It seems that we carry out some actions automatically, for example, jumping to the side to avoid being run over by a car, but even in these cases, our brain manages to very quickly extrapolate past experience to the situation at hand in order to make predictions and determine our behavior.

This January in Cell

An article has been published by a group of Californian researchers who studied the functioning of the rat brain at the critical moment of decision-making. Scientists observed how at this moment the neurons rapidly analyzed the competing options available to the rats. It is possible that the mechanism described in the article underlies not only the ability to make decisions based on a choice of possible actions, but also the ability of animals to anticipate the emergence of more abstract possibilities, which is akin to imagination.

The group of scientists who published the article is led by neuroscientist Loren Frank from the University of California, San Francisco, UCSF. The team examined cellular activity in the hippocampus, a seahorse-shaped region of the brain known to play an important role in navigation and the storage and retrieval of memories. Scientists paid special attention to place cells—neurons nicknamed the “GPS of the brain,” which mentally display the location of the animal as it moves in space.

It has been shown that when an animal performs locomotion, place cells quickly “shoot” in certain bursts. This activity reflects the space within the range of motion, from what is immediately behind to what is directly in front of the animal. (According to the data obtained, mental coverage of the front space also carries information about the location of goals or rewards). These patterns of neural activity, called theta rhythms, repeat approximately eight times per second in rats and represent the animals' constantly updated virtual trajectory of movement.

Now Frank and his team have discovered that when an animal is about to act, neural activity associated with theta rhythms races back and forth along all sorts of future paths—not only to predict what is going to happen, but also to a kind of high-speed, scurrying back and forth, tasting dishes from the buffet of upcoming options for action.

Alternating scenarios in brain waves

The researchers trained rats to choose alternative routes in a W-shaped maze and recorded the activity of place cells using electrodes. Once in the central bend of the maze, the animals turned either left or right. Scientists noticed that as soon as the rodents were at the point of choosing the direction of further movement, their place cells began to behave somewhat strangely.

The rat brain has those place cells that “shoot” in the center of the maze just before (and at the very moment of) turning left, and others that “shoot” before (and at the very moment) turning right. It seemed logical that in a rat that found itself at a bending point, both sets of cells could sometimes “fire” together: at a given point in the maze, the joint activity of all these cells would reflect the choice situation in which the animal found itself. However, this has never been observed.

“It is possible that the mechanism described in the article underlies not only the ability to make decisions based on a choice of possible actions, but also the ability of animals to anticipate the emergence of more abstract possibilities, which is akin to imagination.”

Instead, sets of cells were “fired” one at a time. It was as if before the animal decided where to go, its hippocampus analyzed both the "left" and "right" versions of future locations, mentally alternating between them and never allowing them to connect.

“The brain was very careful not to mix these things up,” Frank emphasizes. “It was unclear why.”

Similar kinds of mental movements back and forth through potential futures that occur in the place cells of animals forced to navigate mazes have already been described in the work of David Redish, a neuroscientist at the University of Minnesota, and the late Adam Johnson ( Adam Johnson). However, these mental movements seemed to be associated with more deliberate actions. Moreover, Redish and Johnson did not investigate whether “left” or “right” representations arise randomly or systematically.

In contrast, the UCSF team found that the alternations it discovered were always closely aligned with other theta cycles. During one cycle, the hippocampus generated an image of turning left, and then switched to the opposite image, creating it during another, next cycle. These scenarios did not always alternate in the same way throughout the experiment—sometimes the same scenario persisted for several runs—but the structure of the signals remained the same. Apparently, the 125-ms sequences separated the brain's different hypotheses about the future in such a way that it resulted in a continuous and consistent overall structure.

Alternative futures in a cyclic signal.
Illustration: Lucy Reading-Ikkanda / Quanta
.
Translation: “ XX2nd century
”.

“What is surprising is the orderliness. "It's absolutely incredible," says György Buzsáki, a neurologist at the New York University School of Medicine who was not involved in the study. “It’s a one-to-one relationship: one cycle is left, the next is right, then left, the next is right.” According to Buzsáki, the benefit of this strict structure may be that each "What if" scenario? checked in a balanced, orderly manner.

When Frank and his colleagues examined neural activity during theta rhythms more closely, they found that the first part of each cycle corresponded to the rat's current location, and the second part represented the left or right alternative. The whole pattern looks something like this: current location, option to go left, current location, option to go right, and so on.

Keeping all options available

Experiments with rats have revealed other intriguing patterns. For example, researchers have found that during theta rhythms, more than just switches from left to right options and vice versa occur. Apparently, sometimes individual loops include the option to change the route to the opposite direction. This discovery puzzled scientists, because in rats there seemed to be no need to consider this option.

According to Kenneth Kay, PhD from Columbia University and first author of the Cell

, this fact contradicts the idea that the hippocampus merely predicts what the animal will encounter. "This is evidence that cyclic structure may be a universal way of connecting the different things that the hippocampus encodes."

In this case, Frank believes, “it looks like the following reflection is presented in expanded form: “What would happen if I took a different path, and should I turn back?”

It therefore appears that the theta rhythm has a more general purpose when it comes to encoding hypothetical propositions. Each cycle, says Mark Brandon, a neuroscientist at McGill University who was not involved in the study, "has its own specific content." “This could be a 'turn left' or 'turn right' task. But, if we take a broader approach, we can say that in each 125-ms portion of theta oscillations, a specific memory or a specific event occurred is encoded.”

Redish, who was not involved in this study, agrees with Brandon. “It's not just a representation of space, but in some ways the structure of the episode,” he says. “This is truly a reflection on the options available.”

Perhaps, the researchers say, the theta rhythm is a fundamental computational unit that the hippocampus uses to consider such abstract options. In most cases, the content of the cycle is likely to be based on experience, allowing the animal to respond quickly and flexibly to a changing environment—say, when fleeing a predator. However, Fr.

This possibility requires seeing the hippocampus not so much as a region of the brain that, through its memory-related functions, helps make decisions, but rather as a learning structure that generates images of an imagined future and carries out their selection, thereby modeling options for action so that other regions of the brain can evaluate and use. Finding out how all this works, apparently, is only possible if we consider theta rhythms as a starting point.

These subsecond chunks of time may also be extremely important for understanding other cognitive processes and neurological conditions. Often, researchers of neural processes take into account only the average cellular activity observed during the experiment; Frank's team's work demonstrates the importance of analyzing information in extremely short periods of time.

Frank and his colleagues are now studying the mechanism that produces the alternating patterns they observed and how this activity affects other parts of the brain during decision-making. In addition, scientists conduct experiments in a maze that requires choosing from more than two scenarios. Although rats' brain rhythms are different from those of humans, the researchers hope their findings can be extrapolated to many species.

“So far, our knowledge of the fine temporal structure of cognition and imagination is superficial,” says Kay. “It’s a very exciting thing to think about.”

Delta rhythm

Delta rhythm (δ rhythm) - oscillation frequency varies from 1 to 4 Hz. the amplitude ranges from 20-200 μV (high-amplitude waves).

General characteristics.

The delta rhythm (slow waves) is associated with restorative processes, especially during sleep, and low levels of activation. In many neurological and other disorders, delta waves are noticeably enhanced. An excess of enhanced delta waves virtually guarantees the presence of impairments in attention and other cognitive functions. It occurs during natural and narcotic sleep, and is observed in the same way as when recording from areas of the cortex bordering the area affected by the tumor.

Theta rhythm

Theta rhythm (θ rhythm) - the oscillation frequency of this rhythm is from 4 to 8 Hz. The amplitude ranges from 20 to 100 µV. Registered in the frontal zones and hippocampus.

General characteristics.

Theta waves appear when a calm, relaxed wakefulness turns into drowsiness. Vibrations in the brain become slower and more rhythmic. This state is also called “twilight”, since in it a person is between sleep and wakefulness. Normally, theta waves are associated with changes in the state of consciousness. Often this state is accompanied by the vision of unexpected, dream-like images, accompanied by vivid memories. Most people fall asleep as soon as a noticeable amount of theta waves appear in the brain.

The theta rhythm is associated with search behavior, increases with emotional stress, and is often observed in psychotic disorders, states of confusion, and concussions.

A high level of theta rhythm can indicate a state of drowsiness and fatigue, which can be a manifestation of asthenic syndrome, chronic stress.

Frequencies or rhythms of the human brain: advantages, disadvantages, control

Our brain, as numerous studies show, depending on the type of activity we are engaged in and the state in which we find ourselves, operates at different frequencies. That is, these are electromagnetic waves that our brain emits during its work, and, depending on how active we are at a given moment in time, whether we are sleeping or awake, these waves can have different frequencies. Scientists believe that thanks to the emission of electromagnetic waves, our brain synchronizes work between individual parts, and, depending on which brain frequencies predominate at a given moment in time, we solve the problems facing us differently and feel differently and we lead. And most importantly, we can control what brain rhythms appear in our head, and we can receive certain benefits of brain wave activity.

In this article you will find a brief description of gamma, beta, alpha, theta and delta frequencies, as well as a table with the advantages of predominance of one or another brain frequency, the disadvantages of excessive frequency activity, as well as ways to increase the activity of brain frequencies.

Gamma wave activity of the brain.

Gamma brain waves are in the frequency range 38 – 70 Hz (in some sources 30 – 100 Hz), have a tiny, almost imperceptible amplitude. Typically associated with increased levels of compassion and happiness, these waves provide a different perspective on reality and increased mental capacity. They can be found in almost every part of our brain, where they serve as a connecting mechanism between all parts of the brain and help improve memory and perception. This is the highest frequency at which the brain operates. This frequency begins to predominate when you are working hard on solving complex logical or mathematical problems.

Beta wave activity of the brain.

Beta brain waves are considered “fast brain waves”, thanks to these waves the active state of the brain is ensured; the brain achieves greater activity with a predominance of gamma waves. When you are awake, beta waves are the predominant frequency of the brain, and to be more precise, they predominate in the left hemisphere. The frequency of beta waves is between 12-38 Hz. Beta mode of the brain is considered normal for adults, this is the state of wakefulness in which we remain during almost the entire day when we are not sleeping. It is believed that the lower your brain frequency, the less active you are in solving problems.

Alpha wave brain activity.

The brain in a state of alpha activity is considered relaxed, I would even say it is a slight relaxation - a state between sleep and wakefulness. Alpha waves range from 8 to 12 Hz and are typically generated in the right hemisphere or synchronously distributed between the right and left hemispheres. A person enters the alpha state when the mind and body are relaxed, in the absence of stress and anxious thoughts. Alpha waves dominate the brains of people who are completely relaxed, creative and clear-minded, and this is also a common state for children. People with a predominant alpha frequency are usually dreamy and have a well-developed imagination. Close your eyes, relax your body, and alpha waves will begin to appear in your head.

Theta wave activity of the brain.

Theta brain activity is considered the next relaxed state of your brain to alpha activity, and typically occurs during the time we dream. The frequency range of theta waves is from 4 to 8 Hz, most of the theta frequencies are generated by the right hemisphere. Theta waves begin to appear in greater numbers when we are least emotional, relaxed, intensely daydreaming, or dreaming. Typically, theta activity is higher in people with attention deficit disorder, as well as in children, and there are slightly fewer theta waves in the brains of creative people than in children.

Delta wave brain activity.

Delta brain waves are considered the lowest brain frequencies at which our brain operates, ranging from 0.5 to 4 Hz. Like other slow brain frequencies, delta waves are generated predominantly in the right hemisphere. The delta brainwave range is associated with empathy, the subconscious, and a reduced sense of awareness. We fall into deep sleep when delta waves begin to dominate other frequencies in our brain, maintaining delta wave activity while awake is almost impossible, but these waves increase in number when we meditate or are half asleep.

Mu rhythm

Mu rhythm (μ rhythm) - often rhythm fluctuations from 8 to 13 Hz. The amplitude usually does not exceed 50 μV. It is registered in the Rolandic region, that is, according to the distribution of the beta rhythm (localized in the region of the Rolandic sulcus).

General characteristics.

It has parameters similar to the alpha rhythm, but differs in the shape of the waves, which have rounded tops and therefore look like arches. Occurs in 10-15% of individuals. Associated with tactile and proprioceptive stimulation and motor imagery. Activated during mental stress and mental stress.

Tau rhythm, lambda rhythm, sleep spindles

The oscillation frequency of the tau rhythm (τ rhythm) lies in the range from 8 to 13 Hz, the oscillation frequency of the lambda rhythm (λ rhythm) and sleep spindles coincides and ranges from 12 to 14 Hz. Registration of tau and lambda rhythms occurs in the temporal cortex of the brain. Sleepy spindles are recorded throughout the cerebral cortex, but are most pronounced in the central leads.

general characteristics

The tau rhythm responds with blockade to sound stimuli. In turn, sleep spindles are peculiar bursts of activity.

Rhythm ratio

When a person is excited or alert, alpha waves are replaced by low-voltage, irregular, fast vibrations. An increase in beta activity with a decrease in alpha activity may indicate an increase in psycho-emotional stress and the appearance of anxiety states (with eyes closed). A decrease in alpha rhythm and an increase in theta rhythm indicates the manifestation of depression (with eyes closed).

Strengthening the beta component and simultaneously weakening the theta component is effective for various epileptic syndromes, attention deficit hyperactivity disorder, post-stroke disorders (spasticity, paresis, plegia), post-traumatic syndromes, etc.

Theta and delta oscillations can occur in a waking person in small quantities and with an amplitude not exceeding the amplitude of the alpha rhythm. The contents of δ and θ are considered pathological if they exceed 40 μV in amplitude and occupy more than 15% of the recording time.

How not to break your watch

What about owls and larks—do they have clocks set differently? We don't really know. Maybe there are also “pigeons” - people who are active during the day, but sleepy in the morning and evening. But it is known for sure that, no matter what kind of bird you are, you need to sleep at night and be awake during the day. This is how we are genetically programmed; to live differently means to shorten our lives.

It is especially harmful to constantly change your routine. For example, scientists from the University of Michigan studied the database of the Nurses Health Study project - a multi-year study of the health of more than 120 thousand American nurses - and found that shift work (both day and night) increases the risk of ischemic stroke by 4% every five years. Other studies based on the same data have shown that working night shifts at least three nights a month for 15 years or more may increase the risk of colorectal cancer as well as breast cancer.

The reason is desynchronosis, that is, a mismatch of biological rhythms, which is a risk factor for the development of cardiovascular diseases and cancer. Desynchronosis is accompanied by prolonged increased fatigue, decreased performance and sleep disturbances.

Single desynchronosis is known to everyone who has experienced jet lag - a syndrome that occurs during a sudden change in time zone, when a person crosses more than three or four time zones. After this, the stage of resynchronization begins - when the biological rhythms of the body adapt to new conditions. Interestingly, if the flight was from east to west, the average recovery speed will be 92 minutes per day, and if from west to east, it will be one and a half times lower, 57 minutes per day. It turns out that it is more difficult to adapt when flying to the east.

Our body also feels desynchronization when we while away time with a smartphone. It is the blue, short-wavelength part of the color spectrum that suppresses the production of melatonin. The photopigment melanopsin in the cells of the retina of the eye reacts to blue light - it is on it that the brain’s opinion of whether it is night or day depends on it. When the light is red, the brain does not understand that it is daytime outside. But gadget screens emit bright and cold blue light, needlessly encouraging the brain in the middle of the night.