home Analyzes How our brain works and how to improve its functioning. How does the human brain work?

How our brain works and how to improve its functioning. How does the human brain work?

The history of computer science as a whole boils down to scientists trying to understand how things work. human brain, and recreate something similar in its capabilities. How exactly do scientists study it? Let’s imagine that in the 21st century, aliens arrive on Earth, having never seen the computers we are used to, and try to study the structure of such a computer. Most likely, they will start by measuring the voltages on the conductors, and will find that the data is transmitted in binary form: exact value voltage is not important, only its presence or absence is important. Then perhaps they will realize that all electronic circuits are made up of the same "logic gates" that have an input and an output, and the signal within the circuit always travels in the same direction. If the aliens are smart enough, they will be able to figure out how combinational circuits work - they alone are enough to build relatively complex computing devices. Maybe aliens will figure out the role of clock signal and feedback; but it is unlikely that they will be able, when studying a modern processor, to recognize in it a von Neumann architecture with shared memory, a program counter, a set of registers, etc. The fact is that after forty years of chasing performance, a whole hierarchy of “memories” with clever synchronization protocols between them appeared in processors; several parallel pipelines equipped with branch predictors, so that the concept of a “program counter” actually loses its meaning; Each instruction has its own register contents associated with it, etc. To implement a microprocessor, several thousand transistors are sufficient; for its productivity to reach the level we are accustomed to, hundreds of millions are required. The point of this example is that to answer the question “how does a computer work?” there is no need to understand the operation of hundreds of millions of transistors: they only obscure simple idea, which underlies the architecture of our computers.

Neuron modeling

The human cerebral cortex consists of about one hundred billion neurons. Historically, scientists studying the functioning of the brain have tried to cover this entire colossal structure with their theory. The structure of the brain is described hierarchically: the cortex consists of lobes, the lobes are made up of “hypercolumns”, those are made up of “minicolumns”... A minicolumn consists of about a hundred individual neurons.

By analogy with the structure of a computer, the vast majority of these neurons are needed for speed and efficiency, for resistance to failures, etc.; but the basic principles of the brain are just as impossible to detect with a microscope, just as it is impossible to detect the program counter by examining a microprocessor under a microscope. Therefore, a more fruitful approach is to try to understand the brain at the lowest level, at the level of individual neurons and their columns; and then, based on their properties, try to guess how the entire brain could work. Something like this, aliens, having understood the operation of logic gates, could eventually build a simple processor out of them - and make sure that it is equivalent in its capabilities to real processors, even though they are much more complex and powerful.

In the picture just above, body neurona (left) - a small red spot at the bottom; all the rest - dendrites, the “inputs” of the neuron, and one axon, "exit". Multi-colored dots along the dendrites are synapses, by which the neuron is connected to the axons of other neurons. The operation of neurons is described very simply: when a voltage “spike” above a threshold level occurs on an axon (typical spike duration is 1 ms, level 100 mV), the synapse “breaks through” and the voltage surge passes to the dendrite. In this case, the surge is “smoothed out”: first, the voltage grows to about 1 mV over 5..20 ms, then decays exponentially; thus, the duration of the burst is extended to ~50ms.

If several synapses of one neuron are activated with a short time interval, then the “smoothed bursts” excited in the neuron by each of them add up. Finally, if enough synapses are active at the same time, then the voltage on the neuron rises above the threshold level, and its own axon “breaks through” the synapses of the neurons connected to it.

The more powerful the initial bursts were, the faster the smoothed bursts grow, and the shorter the delay will be until the next neurons are activated.

In addition, there are “inhibitory neurons”, the activation of which lowers the overall voltage on the neurons connected to it. Such inhibitory neurons make up 15..25% of the total number.

Each neuron has thousands of synapses; but at any given time no more than a tenth of all synapses are active. Neuron reaction time - units of ms; the same order of delay for signal propagation along the dendrite, i.e. these delays have a significant impact on the operation of the neuron. Finally, a pair of neighboring neurons, as a rule, is connected not by one synapse, but by about a dozen - each with its own distance to the bodies of both neurons, and therefore with its own delay duration. In the illustration on the right, two neurons, shown in red and blue, are connected by six synapses.

Each synapse has its own “resistance”, which reduces the incoming signal (in the example above - from 100mV to 1mV). This resistance is dynamically adjusted: if the synapse is activated just before activation of the axon - then, apparently, the signal from this synapse correlates well with the general output, so that the resistance decreases and the signal will make a greater contribution to the voltage on the neuron. If the synapse is activated right after activation of the axon - then, apparently, the signal from this synapse was not related to the activation of the axon, so the resistance of the synapse increases. If two neurons are connected by several synapses with different delay durations, then this adjustment of resistance allows you to choose the optimal delay, or the optimal combination of delays: the signal begins to arrive exactly when it is most useful.

Thus, the model of a neuron adopted by neural network researchers - with a single connection between a pair of neurons and with the instantaneous propagation of a signal from one neuron to another - is very far from the biological picture. In addition, traditional neural networks do not operate time individual bursts, and them frequency: The more frequently the neuron inputs spike, the more frequently the output will spike. Those details of the neuron structure that are discarded in the traditional model - are they essential or unimportant for describing the work of the brain? Neuroscientists have accumulated a huge amount of observations about the structure and behavior of neurons - but which of these observations shed light on the overall picture, and which are just “implementation details” and - like the branch predictor in the processor - do not affect anything other than operational efficiency? James believes that it is precisely the temporal characteristics of the interaction between neurons that allow us to get closer to understanding the issue; that asynchrony is as important for the functioning of the brain as synchrony is for the functioning of the computer.

Another “implementation detail” is the unreliability of the neuron: with some probability it can activate spontaneously, even if the sum of the voltages on its dendrites does not reach the threshold level. Thanks to this, “training” of a column of neurons can begin with any sufficiently large resistance at all synapses: initially, no combination of synapse activations will lead to axon activation; then spontaneous bursts will lead to a decrease in the resistance of synapses that were activated shortly before these spontaneous bursts. In this way, the neuron will begin to recognize specific “patterns” of input bursts. Most importantly, the patterns similar to those on which the neuron was trained will also be recognized, but the spike on the axon will be weaker and/or later, the less the neuron is “confident” of the result. Training a column of neurons is much more efficient than training a conventional neural network: a column of neurons does not need a control response for the samples on which it is trained - in fact, it does not recognizes, A classifies input patterns. Additionally, training a column of neurons localized- the change in synapse resistance depends on the behavior of only two neurons connected by it, and no others. As a result of this, training leads to a change in resistance along the signal path, while when training a neural network, the weights change in the opposite direction: from neurons closest to the output to neurons closest to the input.

For example, here is a column of neurons trained to recognize the burst pattern (8,6,1,6,3,2,5) - the values denote the burst time at each of the inputs. As a result of training, the delays are adjusted to exactly match the recognized pattern, so that the voltage on the axon caused by the correct pattern is the maximum possible (7):

The same column will respond to a similar input pattern (8,5,2,6,3,3,4) with a smaller spike (6), and the voltage reaches the threshold level noticeably later:

Finally, inhibitory neurons can be used to provide “feedback”: for example, as in the illustration on the right, suppressing repeated spikes in the output when the input long time remains active; or suppress a spike in the output if it is too delayed compared to the input signals - to make the classifier more “categorical”; or, in a pattern recognition neural circuit, different classifier columns can be connected by inhibitory neurons so that activation of one classifier automatically suppresses all other classifiers.

Image recognition

To recognize handwritten numbers from the MNIST database (28x28 pixels in grayscale), James assembled an analogue of a five-layer “convolutional neural network” from the classifier columns described above. Each of the 64 columns in the first layer processes a 5x5 pixel fragment from the original image; such fragments overlap. The columns of the second layer process four outputs from the first layer each, which corresponds to an 8x8 pixel fragment from the original image. The third layer has only four columns - each corresponds to a fragment of 16x16 pixels. The fourth layer - the final classifier - divides all images into 16 classes: the class is assigned in accordance with which of the neurons is activated first. Finally, the fifth layer is a classic perceptron that correlates 16 classes with 10 control responses.

Classic neural networks based on MNIST achieve an accuracy of 99.5% and even higher; But according to James, his “hypercolumn” trains in a much smaller number of iterations, due to the fact that changes propagate along the signal path, and therefore affect fewer neurons. As for a classical neural network, the developer of a “hypercolumn” determines only the configuration of connections between neurons, and all the quantitative characteristics of the hypercolumn - i.e. resistance of synapses with different delays - acquired automatically during the learning process. In addition, the operation of a hypercolumn requires an order of magnitude fewer neurons than a neural network with similar capabilities. On the other hand, the simulation of such “analog neurocircuits” on electronic computer somewhat complicated by the fact that, unlike digital circuits that work with discrete signals and discrete time intervals, continuity of voltage changes and asynchrony of neurons are important for the operation of neurocircuits. James claims that a simulation step of 0.1ms is enough for his recognizer to work correctly; but he did not specify how much “real time” the training and operation of a classical neural network takes, and how much it takes to train and operate his simulator. He himself has been retired for a long time, and he devotes his free time to improving his analog neurocircuits.

The history of computer science as a whole boils down to the fact that scientists are trying to understand how the human brain works and recreate something similar in its capabilities. How exactly do scientists study it? Let’s imagine that in the 21st century, aliens arrive on Earth, having never seen the computers we are used to, and try to study the structure of such a computer. Most likely, they will start by measuring the voltages on the conductors, and will find that the data is transmitted in binary form: the exact value of the voltage is not important, only its presence or absence is important. Then perhaps they will realize that all electronic circuits are made up of the same "logic gates" that have an input and an output, and the signal within the circuit always travels in the same direction. If the aliens are smart enough, they will be able to figure out how combinational circuits work - they alone are enough to build relatively complex computing devices. Maybe aliens will figure out the role of clock signal and feedback; but it is unlikely that they will be able, when studying a modern processor, to recognize in it a von Neumann architecture with shared memory, a program counter, a set of registers, etc. The fact is that after forty years of chasing performance, a whole hierarchy of “memories” with clever synchronization protocols between them appeared in processors; several parallel pipelines equipped with branch predictors, so that the concept of a “program counter” actually loses its meaning; Each instruction has its own register contents associated with it, etc. To implement a microprocessor, several thousand transistors are sufficient; for its productivity to reach the level we are accustomed to, hundreds of millions are required. The point of this example is that to answer the question “how does a computer work?” there is no need to understand the operation of hundreds of millions of transistors: they only obscure the simple idea underlying the architecture of our computers.

Neuron modeling

The more powerful the initial bursts were, the faster the smoothed bursts grow, and the shorter the delay will be until the next neurons are activated.

In addition, there are “inhibitory neurons”, the activation of which lowers the overall voltage on the neurons connected to it. Such inhibitory neurons make up 15..25% of the total number.

The same column will respond to a similar input pattern (8,5,2,6,3,3,4) with a smaller spike (6), and the voltage reaches the threshold level noticeably later:

Finally, inhibitory neurons can be used to implement “feedback”: for example, as in the illustration on the right, to suppress repeated bursts in the output when the input remains active for a long time; or suppress a spike in the output if it is too delayed compared to the input signals - to make the classifier more “categorical”; or, in a pattern recognition neural circuit, different classifier columns can be connected by inhibitory neurons so that activation of one classifier automatically suppresses all other classifiers.

Image recognition

Classic neural networks based on MNIST achieve an accuracy of 99.5% and even higher; But according to James, his “hypercolumn” trains in a much smaller number of iterations, due to the fact that changes propagate along the signal path, and therefore affect fewer neurons. As for a classical neural network, the developer of a “hypercolumn” determines only the configuration of connections between neurons, and all the quantitative characteristics of the hypercolumn - i.e. resistance of synapses with different delays - acquired automatically during the learning process. In addition, the operation of a hypercolumn requires an order of magnitude fewer neurons than a neural network with similar capabilities. On the other hand, the simulation of such “analog neurocircuits” on an electronic computer is somewhat complicated by the fact that, unlike digital circuits that work with discrete signals and discrete time intervals, continuity of voltage changes and asynchrony of neurons are important for the operation of neurocircuits. James claims that a simulation step of 0.1ms is enough for his recognizer to work correctly; but he did not specify how much “real time” the training and operation of a classical neural network takes, and how much it takes to train and operate his simulator. He himself has been retired for a long time, and he devotes his free time to improving his analog neurocircuits.

In addition, the cerebellum is also responsible for regulation balance and balance muscle tone, while simultaneously working with muscle memory.

Also interesting is the ability of the cerebellum to adapt to any changes in the perception of information in the shortest possible time. It is implied that even with visual impairment (experiment with an invertoscope), a person adapts to the new state in just a few days and can again coordinate the position of the body, relying on the cerebellum.

Frontal lobes

Frontal lobes- this is a kind of dashboard human body. She supports him in vertical position, allowing you to move freely.

Moreover, precisely due to frontal lobes a person’s curiosity, initiative, activity and independence are “calculated” at the time of making any decisions.

Also one of the main functions of this department is critical self-assessment. Thus, this makes the frontal lobes something of a conscience, at least in relation to social markers of behavior. That is, any social deviations that are unacceptable in society do not pass the control of the frontal lobe, and, accordingly, are not carried out.

Any injuries to this part of the brain are fraught with:

behavioral disorders;
mood changes;
general inadequacy;
the meaninglessness of actions.

Another function of the frontal lobes is arbitrary decisions, and their planning. Also, the development of various skills and abilities depends on the activity of this department. The dominant share of this department is responsible for the development of speech and its further control. Equally important is the ability to think abstractly.

Pituitary

Pituitary often called a medullary appendage. Its functions are limited to the production of hormones responsible for puberty, development and functioning in general.

Essentially, the pituitary gland is something like a chemical laboratory in which it is decided what kind of person you will become as your body grows.

Coordination

Coordination, as the skill of navigating in space and not touching objects with different parts of the body in a random order, is controlled by the cerebellum.

In addition, the cerebellum controls such brain functions as kinetic awareness– in general, this is the highest level of coordination, allowing one to navigate the surrounding space, noting the distance to objects and calculating the possibilities of moving in free zones.

Speech

Such an important function as speech is managed by several departments at once:

Dominant part of the frontal lobe(above), which is responsible for the control of oral speech.
Temporal lobes are responsible for speech recognition.

Basically, we can say that speech is responsible left hemisphere brain, if you do not take into account the division of the telencephalon into various lobes and sections.

Emotions

Emotional regulation is an area controlled by the hypothalamus, along with a number of other important functions.

Strictly speaking, emotions are not created in the hypothalamus, but it is there that influence is produced. endocrine system person. Already after specific set hormones have been produced, a person feels something, however, the gap between the orders of the hypothalamus and the production of hormones can be completely insignificant.

Prefrontal cortex

Functions prefrontal cortex lie in the area of mental and motor activity of the body, which correlates with future goals and plans.

In addition, the prefrontal cortex plays a significant role in creating complex thought patterns,
action plans and algorithms.

home peculiarity the fact is that this part of the brain does not “see” the difference between regulating the internal processes of the body and following the social framework of external behavior.

When you find yourself faced with a difficult choice that was created largely by your own conflicting thoughts, give thanks for it. prefrontal cortex brain. It is there that differentiation and/or integration of various concepts and objects is carried out.

Also in this department it is predicted the result of your actions, and an adjustment is made in comparison with the result that you want to get.

Thus, we're talking about about volitional control, concentration on the subject of work and emotional regulation. That is, if you are constantly distracted while working and cannot concentrate, then the conclusion drawn prefrontal cortex, was disappointing and you won't be able to achieve desired result exactly this way.

The latest proven function of the prefrontal cortex is one of the substrates short term memory.

Memory

Memory is a very broad concept that includes descriptions of higher mental functions that allow one to reproduce previously acquired knowledge, skills and abilities at the right time. All higher animals possess it, however, it is most developed, naturally, in humans.

It is almost impossible to determine exactly which part of the brain is responsible for memory (long-term or short-term). Physiological studies show that areas responsible for storing memories are distributed over the entire surface of the cortex cerebral hemispheres brain.

Mechanism The same way memory works is that a certain combination of neurons is excited in the brain in a strict sequence. These sequences and combinations are called neural networks. Previously, the more common theory was that individual neurons were responsible for memories.

Brain diseases

The brain is an organ like all others in the human body, which means it is also susceptible to various diseases. The list of such diseases is quite extensive.

It will be easier to consider it if you divide them into several groups:

Viral diseases. The most common of these are viral encephalitis (muscle weakness, severe drowsiness, coma, confusion and difficulty thinking in general), encephalomyelitis ( elevated temperature, vomiting, loss of coordination and motor skills of the limbs, dizziness, loss of consciousness), meningitis (high fever, general weakness, vomiting), etc.
Tumor diseases. Their number is also quite large, although not all of them are malignant. Any tumor appears as the final stage of a failure in cell production. Instead of the usual death and subsequent replacement, the cell begins to multiply, filling all the space free from healthy tissue. Symptoms of tumors include headaches and seizures. Their presence can also be easily determined by hallucinations from various receptors, confusion and problems with speech.
Neurodegenerative diseases. By general definition these are also violations in life cycle cells in different parts brain. Thus, Alzheimer's disease is described as impaired conduction of nerve cells, which leads to memory loss. Huntington's disease, in turn, is the result of atrophy of the cerebral cortex. There are other options. The general symptoms are as follows: problems with memory, thinking, gait and motor skills, the presence of convulsions, tremors, spasms or pain. Also read our article about.
Vascular diseases are also quite different, although, in essence, they come down to disturbances in the structure of blood vessels. So, an aneurysm is nothing more than a protrusion of the wall of a certain vessel - which does not make it any less dangerous. Atherosclerosis is a narrowing of blood vessels in the brain, but vascular dementia characterized by their complete destruction.

HUMAN BRAIN
an organ that coordinates and regulates all vital functions of the body and controls behavior. All our thoughts, feelings, sensations, desires and movements are associated with the work of the brain, and if it does not function, the person goes into a vegetative state: the ability to perform any actions, sensations or reactions to external influences is lost. This article is devoted to the human brain, which is more complex and highly organized than the animal brain. However, there are significant similarities in the structure of the brain of humans and other mammals, as well as most vertebrate species. The central nervous system (CNS) consists of the brain and spinal cord. It is connected to various parts of the body by peripheral nerves - motor and sensory.
see also NERVOUS SYSTEM . The brain is a symmetrical structure, like most other parts of the body. At birth, its weight is approximately 0.3 kg, while in an adult it is approx. 1.5 kg. When examining the brain externally, attention is primarily drawn to the two cerebral hemispheres, which hide more deep formations. The surface of the hemispheres is covered with grooves and convolutions, increasing the surface of the cortex (the outer layer of the brain). At the back is the cerebellum, the surface of which is more finely indented. Below the cerebral hemispheres is the brain stem, which passes into the spinal cord. Nerves extend from the trunk and spinal cord, along which information from internal and external receptors flows to the brain, and in the opposite direction signals go to the muscles and glands. 12 pairs of cranial nerves arise from the brain. Inside the brain there are Gray matter, consisting mainly of nerve cell bodies and forming the cortex, and white matter - nerve fibers that form pathways (tracts) connecting various parts of the brain, and also form nerves that extend beyond the central nervous system and go to various organs. The brain and spinal cord are protected by bone cases - the skull and spine. Between the substance of the brain and the bone walls there are three membranes: the outer one is the dura mater, the inner one is the soft one, and between them is the thin arachnoid membrane. The space between the membranes is filled with cerebrospinal fluid, which is similar in composition to blood plasma, is produced in the intracerebral cavities (ventricles of the brain) and circulates in the brain and spinal cord, supplying it with nutrients and other factors necessary for life. Blood supply to the brain is provided primarily by the carotid arteries; at the base of the brain they are divided into large branches going to its various parts. Although the brain weighs only 2.5% of the body's weight, it constantly receives, day and night, 20% of the blood circulating in the body and, accordingly, oxygen. The energy reserves of the brain itself are extremely small, so it is extremely dependent on the supply of oxygen. There are protective mechanisms that can maintain cerebral blood flow in the event of bleeding or injury. Feature cerebral circulation is also the presence of the so-called blood-brain barrier. It consists of several membranes that limit the permeability of the vascular walls and the flow of many compounds from the blood into the brain matter; thus, this barrier performs protective functions. For example, many medicinal substances do not penetrate through it.
BRAIN CELLS
The cells of the central nervous system are called neurons; their function is information processing. There are from 5 to 20 billion neurons in the human brain. The brain also contains glial cells, there are about 10 times more of them than neurons. Glia fill the space between neurons, forming a supporting frame nerve tissue, and also performs metabolic and other functions.

The neuron, like all other cells, is surrounded by a semipermeable (plasma) membrane. Two types of processes extend from the cell body - dendrites and axons. Most neurons have many branching dendrites but only one axon. Dendrites are usually very short, while the length of the axon varies from a few centimeters to several meters. The body of a neuron contains a nucleus and other organelles, the same as those found in other cells of the body (see also CELL).
Nerve impulses. The transmission of information in the brain, as well as in the nervous system as a whole, is carried out through nerve impulses. They spread in the direction from the cell body to the terminal section of the axon, which can branch, forming many endings that contact other neurons through a narrow gap - the synapse; the transmission of impulses through the synapse is mediated by chemicals - neurotransmitters. A nerve impulse usually originates in dendrites - thin branching processes of a neuron that specialize in receiving information from other neurons and transmitting it to the neuron's body. There are thousands of synapses on dendrites and, to a lesser extent, on the cell body; It is through synapses that the axon, carrying information from the neuron body, transmits it to the dendrites of other neurons. The axon terminal, which forms the presynaptic part of the synapse, contains small vesicles containing the neurotransmitter. When the impulse reaches the presynaptic membrane, the neurotransmitter from the vesicle is released into the synaptic cleft. The axon terminal contains only one type of neurotransmitter, often in combination with one or more types of neuromodulators (see Brain Neurochemistry below). The neurotransmitter released from the presynaptic membrane of the axon binds to receptors on the dendrites of the postsynaptic neuron. The brain uses a variety of neurotransmitters, each of which binds to its own specific receptor. Connected to receptors on dendrites are channels in the semipermeable postsynaptic membrane, which control the movement of ions across the membrane. At rest, a neuron has an electrical potential of 70 millivolts (resting potential), while inner side the membrane is charged negatively in relation to the outer one. Although there are various transmitters, they all have either an excitatory or inhibitory effect on the postsynaptic neuron. The exciting influence is realized through increasing the flow of certain ions, mainly sodium and potassium, through the membrane. As a result, a negative charge inner surface decreases - depolarization occurs. The inhibitory effect is carried out mainly through a change in the flow of potassium and chlorides, as a result of which the negative charge of the inner surface becomes greater than at rest, and hyperpolarization occurs. The function of a neuron is to integrate all the influences perceived through the synapses on its body and dendrites. Since these influences can be excitatory or inhibitory and do not coincide in time, the neuron must calculate overall effect synaptic activity as a function of time. If the excitatory effect prevails over the inhibitory one and the depolarization of the membrane exceeds the threshold value, activation of a certain part of the neuron membrane occurs - in the region of the base of its axon (axon tubercle). Here, as a result of the opening of channels for sodium and potassium ions, an action potential (nerve impulse) occurs. This potential propagates further along the axon to its end at a speed of 0.1 m/s to 100 m/s (the thicker the axon, the higher the conduction speed). When the action potential reaches the axon terminal, another type of ion channel that depends on the potential difference is activated: calcium channels. Through them, calcium enters the axon, which leads to the mobilization of vesicles with the neurotransmitter, which approach the presynaptic membrane, merge with it and release the neurotransmitter into the synapse.
Myelin and glial cells. Many axons are covered with a myelin sheath, which is formed by the repeatedly twisted membrane of glial cells. Myelin is composed primarily of lipids, which gives the white matter of the brain and spinal cord its characteristic appearance. Thanks to the myelin sheath, the speed of the action potential along the axon increases, since ions can move through the axon membrane only in places not covered with myelin - the so-called. Ranvier interceptions. Between interceptions, impulses are conducted along the myelin sheath as if through an electrical cable. Since the opening of a channel and the passage of ions through it takes some time, eliminating the constant opening of the channels and limiting their scope to small areas of the membrane that are not covered with myelin speeds up the conduction of impulses along the axon by about 10 times. Only a portion of glial cells participate in the formation of the myelin sheath of nerves (Schwann cells) or nerve tracts (oligodendrocytes). Much more numerous glial cells (astrocytes, microgliocytes) perform other functions: they form the supporting framework of nervous tissue, provide its metabolic needs and recovery after injuries and infections.
HOW THE BRAIN WORKS
Let's look at a simple example. What happens when we pick up a pencil lying on the table? The light reflected from the pencil is focused in the eye by the lens and directed to the retina, where the image of the pencil appears; it is perceived by the corresponding cells, from which the signal goes to the main sensitive transmitting nuclei of the brain, located in the thalamus (visual thalamus), mainly in that part of it called the lateral geniculate body. There, numerous neurons are activated that respond to the distribution of light and darkness. The axons of the neurons of the lateral geniculate body go to the primary visual cortex, located in the occipital lobe of the cerebral hemispheres. Impulses coming from the thalamus to this part of the cortex are converted into a complex sequence of discharges of cortical neurons, some of which react to the boundary between the pencil and the table, others to the corners in the pencil’s image, etc. From the primary visual cortex, information travels along axons to the associative visual cortex, where image recognition occurs, in this case a pencil. Recognition in this part of the cortex is based on previously accumulated knowledge about the external outlines of objects. Planning a movement (i.e., picking up a pencil) probably occurs in the frontal cortex of the cerebral hemispheres. In the same area of the cortex there are motor neurons that give commands to the muscles of the hand and fingers. The approach of the hand to the pencil is controlled visual system and interoceptors that perceive the position of muscles and joints, information from which enters the central nervous system. When we take a pencil in our hand, the pressure receptors in our fingertips tell us whether our fingers have a good grip on the pencil and how much force must be exerted to hold it. If we want to write our name in pencil, other information stored in the brain will need to be activated to enable this more complex movement, and visual control will help improve its accuracy. The example above shows that performing a fairly simple action involves large areas of the brain, extending from the cortex to the subcortical regions. In more complex behaviors involving speech or thinking, other neural circuits are activated, covering even larger areas of the brain.
MAIN PARTS OF THE BRAIN
The brain can be roughly divided into three main parts: the forebrain, the brainstem, and the cerebellum. The forebrain contains the cerebral hemispheres, thalamus, hypothalamus and pituitary gland (one of the most important neuroendocrine glands). The brain stem consists of the medulla oblongata, pons (pons) and midbrain. The cerebral hemispheres are the largest part of the brain, accounting for approximately 70% of its weight in adults. Normally, the hemispheres are symmetrical. They are connected to each other by a massive bundle of axons (corpus callosum), which ensures the exchange of information.

Each hemisphere consists of four lobes: frontal, parietal, temporal and occipital. The cortex of the frontal lobes contains centers that regulate motor activity, and also, probably, centers of planning and foresight. In the cortex of the parietal lobes, located behind the frontal lobes, there are zones of bodily sensations, including touch and joint-muscular sensation. Adjacent to the parietal lobe is the temporal lobe, in which the primary auditory cortex, as well as the centers of speech and other higher functions, are located. Posterior sections the brain is occupied by the occipital lobe, located above the cerebellum; its cortex contains areas of visual sensation.

Areas of the cortex not directly associated with the regulation of movements or the analysis of sensory information are called the associative cortex. In these specialized zones, associative connections are formed between different areas and parts of the brain and the information coming from them is integrated. The association cortex supports complex functions such as learning, memory, language, and thinking.
Subcortical structures. Below the cortex lies a number of important brain structures, or nuclei, which are collections of neurons. These include the thalamus, basal ganglia and hypothalamus. The thalamus is the main sensory transmitting nucleus; it receives information from the senses and, in turn, forwards it to the appropriate parts of the sensory cortex. It also contains nonspecific zones that are connected to almost the entire cortex and probably provide the processes of its activation and maintenance of wakefulness and attention. The basal ganglia are a collection of nuclei (the so-called putamen, globus pallidus and caudate nucleus) that are involved in the regulation of coordinated movements (starting and stopping them). The hypothalamus is a small region at the base of the brain that lies beneath the thalamus. Richly supplied with blood, the hypothalamus is an important center that controls the homeostatic functions of the body. It produces substances that regulate the synthesis and release of pituitary hormones (see also pituitary gland). The hypothalamus contains many nuclei that perform specific functions, such as regulation of water metabolism, distribution of stored fat, body temperature, sexual behavior, sleep and wakefulness. The brain stem is located at the base of the skull. It connects the spinal cord to the forebrain and consists of the medulla oblongata, pons, midbrain and diencephalon. Through the midbrain and diencephalon, as well as through the entire trunk, there are motor pathways going to the spinal cord, as well as some sensory pathways from the spinal cord to the overlying parts of the brain. Below the midbrain there is a bridge connected by nerve fibers to the cerebellum. The most Bottom part trunk - the medulla oblongata - directly passes into the spinal cord. In the medulla oblongata there are centers that regulate the activity of the heart and breathing depending on external circumstances, as well as control blood pressure, peristalsis of the stomach and intestines. At the level of the brainstem, the pathways connecting each of the cerebral hemispheres with the cerebellum intersect. Therefore, each hemisphere controls the opposite side of the body and is connected to the opposite hemisphere of the cerebellum. The cerebellum is located under the occipital lobes of the cerebral hemispheres. Through the pathways of the bridge, it is connected to the overlying parts of the brain. The cerebellum regulates fine automatic movements, coordinating the activity of various muscle groups when performing stereotypical behavioral acts; he also constantly controls the position of the head, torso and limbs, i.e. participates in maintaining balance. According to recent data, the cerebellum plays a very significant role in the formation of motor skills, helping to remember sequences of movements.
Other systems. The limbic system is a broad network of interconnected areas of the brain that regulate emotional states and support learning and memory. The nuclei that form the limbic system include amygdala and hippocampus (part of the temporal lobe), as well as the hypothalamus and the so-called nuclei. transparent septum (located in the subcortical regions of the brain). The reticular formation is a network of neurons that extends through the entire trunk to the thalamus and is further connected with large areas of the cortex. It is involved in the regulation of sleep and wakefulness, maintains the active state of the cortex and promotes focusing attention on certain objects.
ELECTRICAL ACTIVITY OF THE BRAIN
Using electrodes placed on the surface of the head or inserted into the brain, it is possible to record the electrical activity of the brain caused by the discharges of its cells. Recording the electrical activity of the brain using electrodes on the surface of the head is called an electroencephalogram (EEG). It does not allow recording the discharge of an individual neuron. Only as a result of the synchronized activity of thousands or millions of neurons do noticeable oscillations (waves) appear in the recorded curve.

With continuous recording of the EEG, cyclic changes are revealed, reflecting general level individual activity. In a state of active wakefulness, the EEG records low-amplitude, non-rhythmic beta waves. In a state of relaxed wakefulness with eyes closed alpha waves predominate with a frequency of 7-12 cycles per second. The onset of sleep is indicated by the appearance of high-amplitude slow waves (delta waves). During periods of dreaming sleep, beta waves reappear on the EEG, and the EEG may give the false impression that the person is awake (hence the term “paradoxical sleep”). Dreams are often accompanied by rapid eye movements (with the eyelids closed). Therefore, dreaming sleep is also called rapid eye movement sleep (see also SLEEP). EEG allows you to diagnose some brain diseases, in particular epilepsy
(see EPILEPSY). If you record the electrical activity of the brain during the action of a certain stimulus (visual, auditory or tactile), then you can identify the so-called. evoked potentials are synchronous discharges of a certain group of neurons that occur in response to a specific external stimulus. The study of evoked potentials made it possible to clarify the localization brain functions, in particular, to connect speech function with certain areas of the temporal and frontal lobes. This study also helps to assess the condition sensory systems in patients with sensory impairment.
BRAIN NEUROCHEMISTRY
The most important neurotransmitters in the brain include acetylcholine, norepinephrine, serotonin, dopamine, glutamate, gamma-aminobutyric acid(GABA), endorphins and enkephalins. In addition to these well-known substances, the brain probably functions a large number of others not yet studied. Some neurotransmitters only act in certain areas of the brain. Thus, endorphins and enkephalins are found only in the pathways that conduct pain impulses. Other neurotransmitters, such as glutamate or GABA, are more widely distributed.
Action of neurotransmitters. As already noted, neurotransmitters, acting on the postsynaptic membrane, change its conductivity for ions. This often occurs through activation of a second messenger system in the postsynaptic neuron, such as cyclic adenosine monophosphate (cAMP). The action of neurotransmitters can be modified by another class of neurochemicals - peptide neuromodulators. Released by the presynaptic membrane simultaneously with the transmitter, they have the ability to enhance or otherwise alter the effect of transmitters on the postsynaptic membrane. Important has a recently discovered endorphin-enkephalin system. Enkephalins and endorphins are small peptides that inhibit the conduction of pain impulses by binding to receptors in the central nervous system, including higher zones bark. This family of neurotransmitters suppresses the subjective perception of pain. Psychoactive drugs- substances that can specifically bind to certain receptors in the brain and cause changes in behavior. Several mechanisms of their action have been identified. Some affect the synthesis of neurotransmitters, others affect their accumulation and release from synaptic vesicles (for example, amphetamine causes the rapid release of norepinephrine). The third mechanism is to bind to receptors and imitate the action of a natural neurotransmitter, for example, the effect of LSD (lysergic acid diethylamide) is attributed to its ability to bind to serotonin receptors. The fourth type of drug action is receptor blockade, i.e. antagonism with neurotransmitters. Commonly used antipsychotics such as phenothiazines (eg, chlorpromazine or aminazine) block dopamine receptors and thereby reduce the effect of dopamine on postsynaptic neurons. Finally, the last common mechanism of action is inhibition of neurotransmitter inactivation (many pesticides interfere with the inactivation of acetylcholine). It has long been known that morphine (a purified product of the opium poppy) has not only a pronounced analgesic effect, but also the property of causing euphoria. That is why it is used as a drug. The effect of morphine is associated with its ability to bind to receptors of the human endorphin-enkephalin system (see also DRUG). This is just one of many examples that a chemical substance of a different biological origin (in this case, plant) can influence the functioning of the brain of animals and humans by interacting with specific neurotransmitter systems. Another well-known example is curare, which is derived from a tropical plant and can block acetylcholine receptors. Indians South America they lubricated arrowheads with curare, using its paralyzing effect associated with the blockade of neuromuscular transmission.
BRAIN RESEARCH
Brain research is difficult for two main reasons. Firstly, direct access to the brain, which is well protected by the skull, is not possible. Secondly, brain neurons do not regenerate, so any intervention can lead to irreversible damage. Despite these difficulties, research on the brain and some forms of its treatment (primarily neurosurgery) have been known since ancient times. Archaeological finds show that already in ancient times man performed craniotomy to gain access to the brain. Particularly intensive brain research was carried out during periods of war, when a variety of traumatic brain injuries could be observed. Brain damage as a result of a wound at the front or an injury received in peacetime is a kind of analogue of an experiment in which certain areas of the brain are destroyed. Because it's the only thing possible form"experiment" on the human brain, others important method research began with experiments on laboratory animals. By observing the behavioral or physiological consequences of damage to a particular brain structure, one can judge its function. The electrical activity of the brain in experimental animals is recorded using electrodes placed on the surface of the head or brain or inserted into the brain substance. In this way, it is possible to determine the activity of small groups of neurons or individual neurons, as well as to detect changes in ion flows across the membrane. Using a stereotactic device, which allows you to insert an electrode into a certain point of the brain, its inaccessible deep parts are examined. Another approach is to remove small sections of living brain tissue, then maintain it in the form of a slice placed in a nutrient medium, or the cells are isolated and studied in cell cultures. In the first case, it is possible to study the interaction of neurons, in the second - the vital activity of individual cells. When studying the electrical activity of individual neurons or their groups in different areas of the brain, the initial activity is usually recorded first, then the effect of a particular influence on cell function is determined. Another method uses an electrical impulse through an implanted electrode to artificially activate nearby neurons. This way you can study the effect of certain areas of the brain on other areas of the brain. This method of electrical stimulation has proven useful in the study of brainstem activating systems passing through the midbrain; it is also used when trying to understand how learning and memory processes occur at the synaptic level. Already a hundred years ago it became clear that the functions of the left and right hemispheres are different. The French surgeon P. Broca, observing patients with cerebrovascular accident (stroke), discovered that only patients with damage to the left hemisphere suffered from speech disorders. Subsequently, studies of hemispheric specialization were continued using other methods, such as EEG recording and evoked potentials. IN last years Complex technologies are used to obtain images (visualization) of the brain. Thus, computed tomography (CT) has revolutionized clinical neurology, making it possible to obtain intravital detailed (layer-by-layer) images of brain structures. Another imaging technique, positron emission tomography (PET), provides a picture of the metabolic activity of the brain. In this case, a person is injected with a short-lived radioisotope, which accumulates in various parts of the brain, and the more, the higher their metabolic activity. Using PET, it was also shown that speech functions in the majority of those examined were associated with the left hemisphere. Because the brain operates using a huge number of parallel structures, PET provides information about brain function that cannot be obtained using single electrodes. As a rule, brain studies are carried out using a complex of methods. For example, the American neurobiologist R. Sperry and his colleagues performed transection as a therapeutic procedure corpus callosum(a bundle of axons connecting both hemispheres) in some patients with epilepsy. Subsequently, the specialization of the hemispheres was studied in these split-brain patients. It was found that the dominant (usually left) hemisphere is primarily responsible for speech and other logical and analytical functions, while the non-dominant hemisphere analyzes spatiotemporal parameters external environment. So, it is activated when we listen to music. The mosaic pattern of brain activity suggests that numerous specialized areas exist within the cortex and subcortical structures; the simultaneous activity of these areas supports the concept of the brain as a parallel processing computing device. With the advent of new research methods, ideas about brain function are likely to change. The use of devices that make it possible to obtain a “map” of the metabolic activity of various parts of the brain, as well as the use of molecular genetic approaches should deepen our knowledge of the processes occurring in the brain.
see also NEUROPSYCHOLOGY.
COMPARATIVE ANATOMY
U various types The brain structure of vertebrates is remarkably similar. When compared at the neuronal level, there are clear similarities in characteristics such as the neurotransmitters used, fluctuations in ion concentrations, cell types and physiological functions. Fundamental differences are revealed only when compared with invertebrates. Invertebrate neurons are much larger; often they are connected to each other not by chemical, but by electrical synapses, which are rarely found in the human brain. In the nervous system of invertebrates, some neurotransmitters are detected that are not characteristic of vertebrates. Among vertebrates, differences in the structure of the brain concern mainly the relationship of its individual structures. By assessing the similarities and differences in the brains of fish, amphibians, reptiles, birds, and mammals (including humans), several general patterns can be derived. Firstly, in all these animals the structure and functions of neurons are the same. Secondly, the structure and functions of the spinal cord and brain stem are very similar. Thirdly, the evolution of mammals is accompanied by a pronounced increase in cortical structures, which reach their maximum development in primates. In amphibians, the bark is only a small part brain, whereas in humans it is the dominant structure. It is believed, however, that the principles of functioning of the brain of all vertebrates are almost the same. The differences are determined by the number of interneuron connections and interactions, which is higher the more complex the brain is organized. see also

We have written a lot about what types of thinking exist, how our way of thinking affects our lives, but have you thought about how specific the work of our brain is? Does ambient temperature affect its productivity? At what time of day are you most mentally active? Does talking to yourself help you think better?

Our brains are infinitely complex. As we learn something new about him, we add even more questions to the unknown. Before you get behind the wheel of a car, you learn about the mechanisms of its operation, so your main center information processing should not be an exception. We'll tell you something you probably didn't know.

How much energy does the brain use?

An amazing fact is that during the active process of thinking you use a little more energy than when the brain is in a calm state. The energy consumed is almost the same as when relaxing or watching a show. In other words, in those moments when brain activity smallest. Scientists from Pennsylvania came to this conclusion when they conducted their experiment, which consisted of comparing the oxygen consumption of people who were idle and those who solved difficult mathematical problems. The difference was minimal. We can say that the energy consumed by the brain is needed only to maintain its vital functions.

What stage of solving any problems is the most labor-intensive for the brain?

You will be surprised, but you spend much more energy preparing to solve a problem, that is, at the moment when you think about it. At the very moment of solution, much less energy consumption is required. This once again proves that if you have some problems that need to be solved, then it’s better not to think about them, but get down to business right away. You will save both nerves and energy.

Does the body tense up while the brain is working?

An experiment was conducted in which a device to measure muscle activity and a device to measure brain activity were connected to the subject's body. It has been discovered that while a person makes strong mental efforts, tension spreads through the body like waves. That is, at the moment when one muscle relaxes, another begins to tense, and so on throughout the body.

What time of day is best for mental work?

It can be individual for everyone. An ideal time to be active brain activity is the middle of waking time, but better job start a couple of hours after waking up. The important fact is that active and productive is 3 to 5 hours maximum.

Do we think faster than we speak?

Much, much faster. Research at the Department of Psychology has shown that a common person speaks at a speed of 125 to 169 words per minute, and thinks 4 times faster.

Is it good to talk to yourself?

Undoubtedly. Dr. Albert Goss, professor of psychology at the University of California, suggests that the measure of human intelligence may be based on how well we can communicate with ourselves. Someone even manages to conduct such a dialogue out loud, although there are not very many such people.

Often we pronounce the actions that need to be performed, for example, to remember the road, we will mention each turn, and this helps to remember the route. When going to the store, you can often meet people muttering to themselves: bread, milk, sausage, chocolate... We do this to better assimilate information and use it at the right time.

How much memory does the brain have?

Our memory is a universal thing, because some memories can be deliberately erased by the brain, as they cause trauma to mental health. The size of each person's brain is a little different, but the amount of memory it can store is phenomenal. If measured by books, the brain is capable of storing about nine million volumes of information. In other words, you are unlikely to ever overload him with information.

Which part of the brain do we really need?

Apparently, we could function normally with half our brain. Proof of this are numerous cases confirming this fact. Many people who have had surgery to remove part of their brain due to tumors have continued their lives successfully. labor activity, including many doctors, lawyers, engineers and other professions. A similar study was conducted among veterans who received penetrating head wounds during combat. After recovery, they passed the same test as when enlisting. The results were no worse. When one area of the brain is severely damaged, another is able to take over its functions, so that a person’s intellectual abilities are practically not impaired.

Intelligence and manual dexterity are equivalent

Oddly enough, but yes, the more dexterous a person is, the more intelligence he is gifted with. This does not mean that people with "holey hands" are universally stupid, but those who can coordinate the work of their hands and head at the same time are more likely to have high intelligence.

Is it possible to study while sleeping?

Chances are, you've heard plenty of stories about people going to bed with headphones on while listening to lectures or information that needs to be absorbed. Since we have several stages of sleep, brain activity changes as we move from one phase to another. An experiment was conducted in which the subject went to bed wearing headphones and listened to a lecture on history. Sensors monitored his condition, and when he fell asleep, scientists recorded at what point in the lecture this happened. The next morning, the subject remembered everything he listened to, even when he was in a sleepy state, but could not remember a single word of what sounded in his headphones after he fell asleep.

The mental abilities of women and men differ

No, studies have shown that the mental abilities of women and men are the same, but they are different. So, under equal conditions, men cope 50% better with emergency situations than women, nevertheless, the concept of intelligence is formed from many factors. Men better than women in history, they are better oriented in terrain and space, while women are superior to men in learning languages, spelling and arithmetic.

Is there a connection between genius and madness?