The brain of any living thing - perhaps the most mysterious and little-studied organ. The functioning of certain types of cells and parts of the brain is clearly elucidated and described, but science has not yet succeeded in explaining how the brain functions as a whole. Although, for the sake of authenticity, it must be said that in recent years, progress in such studies has nevertheless been observed.
- ablation method - is to remove one of the parts of the brain and then observe the behavior of the organism;
- transcranial magnetic stimulation - assessment of the excitability of the brain using magnetic impulses.
- electrophysiology - registration of electrical impulses of brain activity;
- electrical stimulation - stimulation of individual areas of the brain using electrical impulses.
Nauchfilm. Brain
Brain size of 20 different living creatures, encephalization index
Conducting research, scientists found that the size of the brain differentiated in different animals, and there is a different ratio of the size of the brain and body weight of a living creature. The greater the brain mass relative to body mass, the more brain tissue is used to solve cognitive tasks. Therefore, it was introduced such a thing as encephalization coefficient - the relative ratio of body weight and brain size of a mammal. It is calculated by the formula:
where m - brain mass, g; M - body weight,
The encephalization index provides an opportunity to explore the potential of various types.
Brain size does not affect intelligence
This axiom should be considered in more detail with examples of animals of various classes and species.
The classification starts with the largest number (the smartest of animals) and continues in descending order.
- Bottle-nosed dolphin. The brain weighs 1550 g, the encephalization rate is 4.14
- Fox - 53g, coefficient = 1.6
- Elephant - 7843 g, coefficient = 1.3
- Dog - 64 g, coefficient = 1.2
- Macaque - 62g, coefficient = 1.19
- Donkey - 370g, coefficient = 1.09
- Cat - 35 g, coefficient = 1.0
- Sparrow - 1.0 g, coefficient = 0.86
- Giraffe - 680g, coefficient = 0.66
- Horse - 510g, coefficient = 0.9
- Sheep - 140g, coefficient = 0.8
- Sperm whale - 7800 g, coefficient = 0.58
- Rabbit - 12g, coefficient = 0.4
- Rat - 2g, coefficient = 0.4
- Rhino - 500g, coefficient = 0.37
- Hedgehog - 3.3g, coefficient = 0.3
- Field mouse - 0.2 g, coefficient = 0.22
- Green lizard 0.1g, coefficient = 0.04
- Housefly - 0.0002g, coefficient = 0.02
- Viper - 0.1 g, coefficient = 0.005
So, the dolphin is the most similar to the person in terms of the encephalization rate.
As you can see, the stereotype about low mental abilities, for example, a donkey, a giraffe and a sheep has no basis.
An interesting fact: there is no brain in insects, the role of the central nervous system is played by the ganglia of the ganglia. Theoretically, if a cockroach is left without a head, he will die from what he cannot eat.
It was also brought that the mental abilities of the organism depend not only on the size of the brain, but to a large extent on the number of connections between neurons.
Prevention of brain drying in humans
It is necessary to consider in more detail the human brain, since it is this organ that can provide answers to the eternal questions concerning our development and life, if studied in more detail.
The brain of a newborn weighs 365 g, child 2 years old - 930 g, 6 years - 1211 g, adult - 1400 The enceffalization rate of the human brain over 18 years old is 6.74.
Interestingly, there is a difference between the brain of a man and a woman. The first recorded studies of the sexual differences of the brain were conducted by Francis Gatton as early as 1882. Later, scientists from reputable, world-renowned research institutes proved that the average male brain is 125 grams. more than a woman’s brain. In addition, there are also racial and national differences. For example, the owners of the lightest brain are the Australians - 1185 g, the heaviest are the Europeans - 1375. Moreover, the British have a brain that weighs an average of 1346 g, the French have 1280 g, the Koreans have 1376 g, the Japanese have 1313 The leaders are Germans, their brains weigh 1425 g. The brain of Russians is 26 grams less than German. African-American brains weigh an average of 1,223 grams, which is 100 grams less than the whites of the US population.
During life, the brain can change its weight in the direction of drying out. Basically, the hippocampus is reduced in people suffering from depression and schizophrenics. Scientists now know that some parts of the brain are aging faster than others. Due to age-related changes, the loss in volume can go up to 10%. Scientists from the Rush University Medical Center have established that deficiency of vitamin B 12, as well as a disease such as diabetes, leads to the drying out of the brain at the highest level.
How to avoid this and prevent the gray matter from drying out?
The answer is simple: you need to often eat foods containing this very vitamin b 12. In the largest quantities it is found in milk, eggs, meat, poultry, fish.
In this regard, beans, beans, bananas, grain bread are very useful - these products contain glucides (slow carbons) that slow down the aging process of the brain. It is necessary to go in for sports: even insignificant loads stimulate the blood saturation with oxygen, respectively, much more nutrients enter the brain. It is very important to establish proper nutrition for oneself, the main rules of which are a limited amount of sweets, as well as diversity in food: the brain does not like diets, where it is necessary to eat monotonously for several weeks.
Only the correct approach to your own lifestyle will help preserve the youth of the brain and increase the level of IQ.
Scientists have long noticed that advanced intelligence and an evolutionary brain are present in humans and other animals, often demonstrating social behavior. This prompted the anthropologist and evolutionary psychologist Robin Dunbar to propose the social brain hypothesis. According to the theory, a person has developed a large brain in order to be able to live in large social groups. Although in the past 20,000 years, due to the “domestication” of man, his brain has decreased in size, but before this, evolution had to quickly increase the brain of hominids in a relatively short period so that people could unite into large tribes.
In social communication, it is very important to recognize the so-called “outside knowledge”, that is, to understand the hierarchy, social interrelations and relationships like “she knows what he knows” and the like. For example, an alpha male in a chimpanzee chooses any females for himself, but he is tolerant of attempts to mate with them from those who helped him reign on the throne. Without a sufficiently advanced brain, such subtleties of the social hierarchy cannot be learned.
Now a group of scientists from the USA and the UK has published a new scientific paper “The social and cultural roots of the brain of whales and dolphins,” which confirms the hypothesis of the social brain.
The representatives of the cetacean group (dolphins and whales) have the most advanced nervous system among all taxonomic groups, and they are highly rated for any characteristic of neuroanatomical complexity. At the same time, many cetaceans are also organized into hierarchical social structures and demonstrate an amazing breadth of cultural and social behavior, the features of which, which are rare for animals, are very similar to the social behavior of humans and primates. But so far very little evidence has been gathered of the correlation between the large brain, social structures and the cultural behavior of cetaceans.
Whales and dolphins have discovered a huge amount of signs of complex social behavior, including:
- relationship in complex alliances;
- social transfer of hunting techniques (training);
- joint hunting;
- complex singing, including singing in regional group dialects;
- speech mimicry (imitation of other people's voices);
- the use of "voice signatures-identifiers", unique to a particular individual;
- interspecific cooperation with humans and other animals;
- alloparental care for someone else's cub (for example, from the side of a female helper or “nurse”);
- social games.
The researchers collected a large array of data for each species of cetaceans: body weight, brain size, the degree of social intercourse on the above characteristics - and calculated the correlation between these indicators. The first diagram below shows the relationship between species and the size of the brain (red corresponds to a larger size, green to a smaller one). The second diagram shows social behavior indicators (social repertoire). In the end, below is a graph of the relationship between these two parameters.
Scientists have found that the evolutionary development of the brain is associated with the social structure of the species and with the size of the group. Moreover, the connection with the size of the group is quadratic, that is, the most developed brain and advanced social behavior demonstrate groups of medium size, and not small or large groups.
The authors of the research point to explicit parallels between marine mammals and primates / humans. In dolphins and whales, there is also a combination of simultaneously large brain, hypersocial behavior and a variety of behavioral patterns. It is these qualities that allowed a person to multiply in incredible quantities and populate the entire Earth. Scientists believe that dolphins and human intellectuals are able to manifest themselves in the course of evolution as a kind of evolutionary reaction to the need to live in a society of their own kind.
The elephant's brain is the largest brain among all land mammals that inhabit our planet. It is located in the back of the head and occupies a small part of the volume of the skull. Consider the main characteristics and characteristics of the brain of these animals, as well as compare it with the human brain.
Types of elephants
Currently, there are three species of these animals on our planet:
- African elephants. They live in most of Africa and are the largest species of terrestrial animals. Large specimens of these animals reach 7.5 meters in length, 3.3 meters in height and weigh up to 6 tons. The tusks of this species of elephants grow all their lives, both in males and females. The African elephant has large ears to release more heat to the atmosphere. This species is endangered due to poaching.
- Indian elephants. This species of elephants lives mainly in India. Its specimens grow up to 6.4 m in length and up to 2-3.5 m in height. The elephant has a dark gray color. It occupies an important place in the culture of India.
- Asian elephants. These elephants are the largest. They reach 6.4 m in length and 3 m in height. The weight of an adult individual is within 5 tons. Unlike the African elephant, they have small ears that constantly move, cooling the head of the animal. Most males do not have tusks.
Some facts about the brain of elephants
Here are the important facts that characterize the brain of the largest land animals on the planet:
- the brain in newly born elephant pups accounts for 35% of the mass of the brain of an adult animal;
- elephants are among the most intelligent animals on earth;
- the brain of an African male has a mass of from 4.2 to 5.4 kilograms, while the brain weight of an African female is 3.6-4.3 kilograms;
- brain development in elephants is similar to that in humans.
The importance of brain size
Despite the fact that the brain of an elephant is the largest in size among mammals on Earth, it occupies only a small zone in the back of the head of the animal. If we take the ratio of brain weight to body weight, it turns out that this figure will be less for elephants than for humans. Anyway, the elephant is the only animal along with primates and sperm whales, which has a fairly high ratio of brain size to body size.
Brain size is important because it correlates with the flexibility of the animal’s thinking or, as they say, with its mind, and also determines the complex social structures and relationships in the population of these animals.
How much does the brain weigh in males and females?
In both African and Indian elephants, the size of the brain depends on whether the individual is a male or female. The brain weight of the male African elephant is greater than the weight of the females of this species, by 0.6–1.1 kg, and is 4.2–5.4 kg. It is important to note that this difference in the weight of the brain of animals does not affect their mental abilities.
Many studies on the behavior of elephants have demonstrated quite reasonable behavior of females, which are not inferior to male elephants. This is explained by the fact that not the weight of the brain itself is important for rational behavior, but the ratio of its mass to the weight of the body. Since females of an elephant are usually smaller than males, the difference in this ratio is almost zero. In addition, the consciousness itself in females is very different from that in males, since they are attached to their mothers and, starting from early childhood, form stable bonds with other females of their herd, which they maintain throughout their lives. Males are more lone nomads.
Brain development
It is interesting to note that the brain of elephants develops like the brain of primates, including humans. An elephant and a person are born with a small brain mass: in an elephant it makes up 35% of the adult brain mass, and in humans it is 26%.
These figures suggest that there is a possibility for significant brain development in animals during their growth. As the brain mass increases, various abilities, including mental ones, are actively developed in young elephants. Studies on the behavior of elephants, as well as the anatomy of their brains, suggest that elephants are very intelligent animals.
Elephants are intelligent animals
Thanks to a developed brain, elephants remember the location of oases with water during a drought period, they are able to recognize the bones of their dead relatives. They can even love. Elephants are able to identify whether a given person is dangerous for them or not, since animals distinguish people of different ethnic groups, human languages, age and gender. Dolphins and whales have similar abilities. It has been observed that young elephants learn from their older relatives throughout their lives.
For example, one of the populations of African elephants lives near the territory where the Masai tribes live. Elephants fear the people of this tribe, since conflicts often erupt between animals and the Masai because of the lack of vital resources, which is a frequent problem in Africa. Animals learned to recognize the smell and red color of the people of the tribe.
Scottish scientists from the University of St. Andrews found that the developed brain of elephants allows them to understand many human gestures without prior training. This fantastic discovery places elephants at the top of the list of animals that can understand humans in sign language. Thanks to this ability of animals, they were able to domesticate and establish a strong friendly connection between the elephant and its owner, despite all the danger of the elephant and its large size.
Comparison of the elephant and human brain
If mental capacity depended only on brain mass, then knowing how much a human’s brain weighs (approximately 1.4 kg), one could say that it is much more stupid than an elephant, because an animal’s brain weighs 3–3.5 times more.
It is also impossible to identify mental abilities with the ratio of the masses of the brain and the body. For example, for a man this indicator is equal to 1/40, and for an elephant - 1/560, but for small birds the ratio is 1/12.
The difference in mental capabilities is not associated with the mass or volume of the brain of an elephant and a person, but with the structural features. Most scientists are inclined to believe that a person’s mental abilities are associated with the complex structure of his cerebral cortex, which includes 16 billion neurons, and by this indicator significantly exceeds the brain of any animal, including an elephant, which has less in the cortex. 3 times neurons than in humans. Each human neuron is capable of forming tens of thousands of connections with others. In addition, all the neurons of the brain are packed in several layers, which leads to an increase in their density, in comparison with the brain of an elephant.
As for the elephant, it should be noted that the structure of the cortex of his brain is different from that of primates. In particular, its composition includes a greater number of cell types, which, according to scientists, plays an important role in the manifestation of the mental abilities of these animals.
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10 place - New brains
There is a myth that, when learning something new, a person has new gyrus. In fact, man is not born with convolutions, at the beginning of development the fetus has a smooth small brain. As they grow, neurons also grow and migrate to different areas of the brain, creating grooves and ridges. By the age of 40 weeks, the brain is almost as tortuous as an adult. That is, as learning new reliefs does not appear, we are simply born with them.
However, as we learn, the brain really changes - plasticity of the brain is responsible for this, but still, new gyrus does not appear.
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9th place - the human brain is the biggest
In proportion to the whole body, the human brain is really quite large, but a common misconception is that the human brain is larger than any other creature.
An adult's brain weighs approximately 1.3 kg and reaches 15 cm in length. The largest brain belongs to the sperm whale; it weighs over 8 kg. Another animal with a large brain is an elephant, its brain weight is about 5 kg.
Many will ask, but what about the ratio of the brain to the body? However, in this case people are inferior. A shrew has a brain weight of 10% of the total mass.
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8th place - The level of intelligence depends on the size of the brain
As practice has shown, the size of the brain does not affect the level of intelligence. For example, the brain of I.S. Turgenev weighed in 2012, and Anatol France’s brain was 1017 g. The heaviest brain, 2850 g, was found in an individual who suffered from epilepsy and idiocy. His brain was functionally inferior. So, there is no direct relationship between the mass of the brain and the mental abilities of the individual.
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7th place - The older the person, the weaker his memory
In fact, in most cases we see just such a picture - in the elderly people the process of thinking slows down, memory deteriorates, in some cases accompanied by senile marasmus.
However, it’s not age that is to blame, but a way of life that is led and led by each individual person. Some people kept their thinking clear to a great age. Of course, one desire is not enough for this - it is necessary to observe a certain mode of work, rest and food. It is advisable to use healthy foods, among which is worth noting fish, fresh fruits and vegetables. Intellectual exercises also keep thinking clear.
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6 place - the brain works like a computer
It is a myth. In fact, if we look at how modern computers work and how the brain works, we will see that the differences between them are fundamental. In a computer, a program stored in memory is executed using a processor, so the memory and calculations are spaced apart. In the brain, this separation is absent, in fact, memory and calculation in it are combined with each other due to the fact that memory is stored in the structure of connections between nerve cells, which perform the calculations.
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5th place - Alcohol kills brain cells
Alcoholism, of course, can lead to serious health problems, but experts do not believe that alcohol is the cause of neuron death. In fact, studies have shown that even constant drinking does not kill neurons.
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4th place - Damage to the brain makes a person a vegetable
It is not always so. There are different types of brain damage, and their effect on a person depends largely on where they are located and how serious they are. Mild concussion-type brain injuries are due to the fact that the brain moves inside the skull, which causes bleeding and tearing. The brain recovers remarkably well from minor injuries, and the vast majority of people who have experienced a slight brain injury do not become disabled for life.
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3rd place - brain hemispheres
The left hemisphere of the brain is responsible for rationality, and the right - for creativity. This is only partly true. The study of gifted schoolchildren, winners of high-level mathematical olympiads, showed that among them were distinct right-handers, left-handers and ambidexters (people with the same sleight of hand), that is, these students had a slightly different distribution of functions in the hemispheres.
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2 place - Brain is gray matter
Many of us have heard that the cells of the cerebral cortex are gray in color, and this statement is not subject to any doubts. However, only the cells of the dead brain, which left the host's body, have gray color. The natural color of the living brain is red. By the way, the brain tissue resembles the structure of the usual soft jelly.
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1st place - Myth of 10% of the used part of the brain
The myth is that most people use no more than 10% of the brain. Neuroscientist Barry Gordon describes the myth as "ridiculously erroneous," adding: "We use almost all parts of the brain, and they are almost always active."
Studies show that each section of the human brain has its own specific set of functions. If the 10% myth is true, then the chance to damage the brain would be much less - we should only worry that the small 10% of our brain would be safe. But in reality, even damage to a very small area of the brain can lead to serious consequences for our functioning. A brain scan also showed that there is a certain level of activity in the whole brain, even during sleep.
It seems that the situation with our brain is simpler than ever - the more “gray matter” the better. However, according to this logic, elephants should have become the dominant species on the planet, and not man. Fortunately for us, a larger brain size does not mean greater efficiency or better cognitive abilities, and sometimes even vice versa. Concepture publishes a translation of an article by Nautilus, in which the nervous system specialist Suzanne Herculano-Huzel talks about why our brain is the most efficient.
Brain mass and thinking
For a long time, we thought that we were the height of cognitive abilities among all animals. But from some rather important points of view, such a loud nomination is by no means a synonym for "the pinnacle of evolution." As Mark Twain noted in 1903, to assume that evolution is a long way leading to man as his last and highest goal would be as ridiculous as thinking that the only goal of building the Eiffel Tower was to paint its top.
In addition, evolution is not synonymous with progress, it is just a change over time. And people are far from being the “youngest”, that is, the recently evolved species. For example, more than 500 new species of cichlids (family of fish) in Lake Victoria (the youngest of the great African lakes) have emerged since its basin was first filled with water 14,500 years ago.
However, there is something truly unique in our brain that makes it able to reflect even on its structure and the reasons for the emergence of the hypothesis of its dominant role in relation to other types of brain. After all, we are the ones who study other animals, and they are not us - a weighty argument in favor of the special nature of the human brain.
The mass of the brain comes to mind as the most obvious solution to the riddle of which brain is best suited to developed thinking: if it is the brain that makes consciousness and cognition possible, the more you have it, the more cognitive abilities you have. But here it is easy, as they say, not to notice an elephant, not only figuratively, but literally: an elephant is a creature whose brain is bigger than a human, but at the same time it does not demonstrate such complex and flexible behavior as we do.
In addition, putting an equal sign between a large brain size and developed cognitive abilities, we assume that all brains are “done” in the same way, that is, we start from a similar ratio of brain size and number of neurons. But my colleagues and I already know that different types of brains are “made” differently.
Primates have a clear advantage over other mammals, which arose due to the confluence of evolutionary circumstances, which made it very “economical” to increase the number of neurons in the brain without the need for a significant increase in the average size of cells, which is observed in the case of other mammals.
“Hello, beauty!” From the late 1960s, psychologists wondered whether the ability to recognize oneself in the mirror was a sign of rationality and self-awareness.
So, besides the difference in the structure of the brain of different types, scientists also know the total number of neurons in some of them, so we can associate more developed cognitive abilities not just with the mass of the brain, which is somewhat rough, but with the number of neurons in it.
In addition, this hypothesis can be tested in practice. The total number of neurons was the next good answer to the question of how well the brain adapts to thinking, regardless of brain size. After all, if it is neurons that are what gives rise to conscious cognitive actions, then a greater number of neurons will mean more developed cognitive abilities. Is not it?
In fact, even though scientists previously believed that cognitive differences between species were qualitative, and some features were generally considered the exclusive prerogative of man, we now realize that cognitive differences between human beings and other animals are rather in their degree. development. In other words, we and animals have quantitative, rather than qualitative, differences.
We have developed an impressively complex ability to use tools, we even make tools to make other tools, but ... chimpanzees use branches as tools for digging out termites, monkeys are learning to use rakes to get food they don’t see, but crows are not only made of wire tools that help them get food, but also set them aside for future use.
Alex, an African gray parrot whose owner was psychologist Irene Pepperberg, learned to pronounce words that symbolized objects, and chimpanzees and gorillas, although they cannot articulate sounds for anatomical reasons, learn to communicate using sign language.
Chimpanzees can master hierarchical sequences: they play games where they have to touch the squares in an ascending order with respect to the numbers previously shown, and they fulfill the requirements of the game as well and as quickly as very trained people. Chimpanzees and elephants can work together to get food that is not accessible to each of them. Chimpanzees, as well as other primates, demonstrate the ability to assess the mental state of others, and this is a necessary prerequisite for the ability to deceive.
Even the birds seem to have an understanding of the mental state of other individuals: for example, magpies can defiantly hide food in the presence of strangers, and then, when strangers leave, pull out food and hide it somewhere else. Chimpanzees and gorillas, elephants, dolphins, and magpies also show signs that they recognize themselves in the mirror, which they use to inspect the label that the researchers put on their heads as part of the experiment.
Does the brain of an African elephant really have more neurons?
We mentioned fundamental discoveries that confirm the cognitive abilities of species that differ from ours, but such isolated observations cannot serve as the basis for the interspecific comparison that we need to make if we want to find out what this is in our brain, which allows it to perform cognitive feats inaccessible to others. And here we are faced with another problem - in fact, the biggest at this stage: how to measure the cognitive abilities of many species and to do it in such a way that for each of them to get values comparable to each other.
In 2014, a study was conducted that focused on self-control (cognitive ability, which is based on the prefrontal, associative part of the cerebral hemispheres cortex) on the example of several species of animals - mostly primates, but also small rodents, dog-like predators, the Asian elephant and some species the birds.
The results of the study showed that the value that best correlated with the correct behavior during the self-control test was absolute brain volume. With the exception of the elephant, which, despite the fact that its brain was the largest among the "participants", was completely unable to complete the task properly.
The reasons for this can come up with a lot, from "He just didn't give a damn about food or a task," to "He liked to annoy researchers with a refusal to perform a task." (I like to think that the reason why monkeys turn out to be so hard to teach actions that people very quickly get used to is that monkeys feel offended by the obviousness of the task: “Come on, you want me to move from place to do so.” ? Give me something more complicated! Give me a video game! ")
Susana Herculano-Hozel explores the question of what exactly makes the human brain so special, allowing it to perform much more complex operations than those to which animals exhibit abilities. Photos from the performance for TED.
From my point of view, the most interesting opportunity to explain the poor results shown by an elephant is the assumption that the African elephant simply does not have all the pre-frontal neurons in the cerebral cortex that are necessary to solve the task of self-control (like those encountered in experiment).
Since we recognized that the brains of primates and rodents are “made” differently and have different numbers of neurons, even if their sizes are comparable, we made a further logical assumption, which said that the brain of an African elephant, if it is arranged according to the type of brain of rodents, there should be only 3 billion neurons in the cerebral cortex and 21 billion neurons in the cerebellum, compared with our 16 billion and 69 billion, respectively.
On the other hand, if the brain of an African elephant is arranged as a primate brain, then it must contain a fabulous number of neurons: 62 billion in the cerebral cortex and 159 billion neurons in the cerebellum. But elephants, of course, do not belong to primates, nor to rodents; They belong to the Afrotheria superorder (Afrotheria), as well as a number of small animals, such as the long-eared jumper and goldfish, which have already been investigated before, and as a result of these studies, scientists have concluded that their brains function very similarly to the brains of rodents.
Why spend $ 100,000 if the butcher’s knife fit?
so , Is it true that the brain of an African elephant, which is more than three times heavier than ours, contains more neurons? If this turns out to be true, then my hypothesis, which states that cognitive abilities are values derived from the number of neurons, will be refuted.
But if it turns out that the human brain has a significantly larger number of neurons than the brain of an African elephant, which is much larger than it, it will support my suggestion that the simplest explanation for the cognitive abilities of the human species is a remarkable number of neurons in the brain that is no longer observed in one species, regardless of the size of its characteristic brain. In particular, I expected the number of neurons in the human cerebral cortex to be greater than in the cortex of the African elephant.
My guess was based on the logic of sources in cognitive science, which for a long time proclaimed the cerebral cortex (or, more precisely, the prefrontal part of the cerebral cortex) as the only “residence” of consciousness, which means abstract thinking, an integrated decision-making process and planning future actions.
However, almost the entire cerebral cortex is connected to the cerebellum by communication loops, which connect the information processing devices of the cortex and cerebellum with each other, and more and more studies have suggested that the cerebellum is involved in the cognitive function of the cerebral cortex. Thus, it can be said that these structures work in tandem. And since these structures together possess the greatest number of neurons in the brain, cognitive abilities must equally well correlate with the number of neurons in the whole brain and in the cerebral cortex, as well as in the cerebellum.
Brain Soup Gallon
The hemisphere of the brain of an African elephant weighs 2.5 kilograms and this meant that it would have to be cut into hundreds of small pieces for processing and counting neurons, since turning the brain into soup to determine the number of neurons can be done only with pieces of tissue no more than 3-5 grams each . I wanted the cuts to be made systematically, and not how God would put it on my soul. There was a question about the most appropriate tool.
Susana Herkulo-Hozel has developed her own method of counting the number of neurons in nervous tissue: for this, a fragment of the brain is exposed to a solvent that dissolves cell membranes, but leaves the nucleus intact. It turns out a kind of "soup." The convenience of counting nuclei in it is ensured by the fact that, if it is thoroughly shaken, the nuclei will be distributed almost evenly in it. After that, it will be possible to calculate the number of nuclei of neurons in 4-5 drops and extrapolate the result to the whole volume - approx. per. by materialsTed.
We used the usual cutter to get a series of thin sections from the hemisphere of the human brain for research. The cutter was convenient to separate the cortical gyrus, but it had one significant drawback: too much brain material remained on the disc-shaped knife, which made it difficult to determine the exact number of cells in the hemisphere. If we wanted to find out the total number of neurons in the elephant's brain, we needed to cut it manually into thicker pieces in order to minimize the inevitable loss, down to a negligible value.
One fine morning, my daughter and I (school holidays had just begun) went to the store of household goods in search of an L-shaped bracket, which was supposed to serve as a stable, flat, regular shape frame for cutting the elephant's brain, as well as the longest knife hold in one hand.
It was an adventure that the teenager could not miss, because years later we could say: “Hey, mom, remember how we cut the elephant's brain?”. Having bought everything we needed and safely drove home, we set to work: for a start, we cut down the structural reinforcement from the L-shaped bracket, then placed an elephant's brain in it. Of course, there are cars worth hundreds of thousands of dollars that would do the job in the most perfect way, but why spend so much money if the usual manual butcher's knife fits?
I laid the hemisphere with the flat side on the work surface and positioned it between the two supports of the bracket. One of the students held the supports in place while I held the hemisphere with my left hand and cut it firmly but carefully. A few cuts later, we had an elephant's brain completely cut and ready for processing: 16 slices through the cerebral cortex, eight through the cerebellum, as well as a whole brain stem and a huge olfactory bulb weighing 20 grams (10 times heavier than the brain of a rat), everything it was decomposed separately.
Counting neurons. Susana Herkulano-Khuzel and her students made sections of the elephant's brain, shown in this photo, to determine the number of neurons it contains and compare it with similar indicators of the human brain.
It was the largest amount of fabric we ever processed. One person, processing one fragment per day, would spend an entire year analyzing such a volume, and working without days off. It was obvious that group work was needed here, especially since I wanted to get results within six months. But even with a small army of assistants consisting of students, the work took a lot of time: two months passed, and we processed only one tenth of the elephant's brain. Something needed to be invented.
Next, we had to internal structures (striatum, thalamus, hippocampus) from the cortex, then cut the cerebral cortex into smaller pieces for processing, and then separate each of these pieces into gray and white matter. In general, we have 381 pieces of fabric, most of which were several times more than 5 grams by weight, and so much can be processed at a time.
The principles of capitalism proved to be most welcome. I did some calculations and found that I have “extra” 2500 dollars - about one dollar per gram of fabric that needs to be processed. I put together a team and made them an offer: anyone can help with the work and at the same time receive a financial reward for it. Small partnerships were quickly formed: one student chopped up the cloth, the second did the counting and both shared the income. The work went like magic.
My husband, arriving at the laboratory, was amazed by the friendly crowd of students, who were talking animatedly among themselves and working diligently (most of the students worked in shifts, since the laboratory was rather small). Jairo Porfirio took a huge amount of work on antibody staining, and I performed the counting of neurons using a microscope and in just six months we processed the entire hemisphere of the brain of an African elephant — as planned.
And the winner is ...
Heed The brain of an African elephant has more neurons than the human brain. And not just a little more: three times more - 257 billion against our 86 billion. But - and this is a truly important "but" - 98 percent of these neurons were located in the cerebellum, in the back of the brain. In the case of any other mammal that we have already investigated, the cerebellum also contained most of the neurons, but this indicator never exceeded 80 percent.
The extraordinary distribution of neurons in the brain of an African elephant left some 5.6 billion neurons in the cerebral cortex. Despite the size of the cortex of the African elephant, 5.6 billion neurons in it fade when compared with an average of 16 billion neurons concentrated in the much more modest human cortex.
So, we received the required answer: no, the human brain does not contain more neurons than the much larger brain of an elephant, but the human cerebral cortex has three times more neurons than the elephant's cerebral cortex, which is larger than the human. Obviously, the huge number of neurons in the elephant's brain does not help him in the development of cognitive abilities. This gives us the right to say that the number of neurons in the cerebellum is not a decisive factor in determining the best fitness of the brain for thinking. .
It turns out that only the cerebral cortex remains. Nature conducted the experiment we needed, proving the lack of connection between the number of neurons in the cerebral cortex and the number of neurons in the cerebellum. The superior cognitive abilities of a person can be explained (and this is the only explanation) simply by an impressively large number of neurons in the cortex of our brain.
Although today we do not have data on the measurement of cognitive abilities that are necessary for comparing all types of mammals, or at least those, the number of neurons in the cerebral cortex of which we know, we can already make verifiable assumptions based on these numbers. If the absolute number of neurons in the cerebral cortex is the main limiting factor in the development of the cognitive abilities of a species, then I assume that the classification by this indicator should look like this:
And this seems to be more plausible than the currently valid classification according to the mass of the brain, which has, for example, a giraffe, above primates. In this interpretation, the hierarchy looks like this:
It turns out that there is a simple explanation for why the human brain and only it can at the same time be so similar to the brain of other species in its evolutionary limitations, and so different from them, endowing us with the ability to reflect on our own material and metaphysical origin.
First, we are primates, and this gives us the advantage of a large number of neurons “packed” in a small cortex. And secondly, thanks to the technological innovations introduced by our ancestors, we avoided the energy limitations that are responsible for the fact that other animals have fewer neurons in the cerebral cortex (after all, only that amount they can afford on a strict diet in the wild nature).
So, in the end, do we have what other animals don't have? I argue that this is a huge number of neurons in the cerebral cortex, the largest in comparison with the currently known species. And what do we do such that no other animal does, and what allowed us to collect so many neurons in one place?
The answer, it seems to me, is very simple: we cook our food. That is, we are able to provide our brain with the nutrition necessary for its development, which is not the case with animals in the wild. And our brain consumes a lot of energy (about 25% of all the energy that we get from food). Thus, simplifying the process of obtaining food and making it more balanced and nutritious, a person contributed to the development of his brain, and the brain, in turn, contributed to the development of human society.
About the author: Susana Herculano-Hozel is a nervous system specialist from Brazil. She is an Adjunct Professor and Head of the Laboratory of Comparative Anatomy at the Institute of Biomedical Sciences of the Federal Institute of Rio de Janeiro.
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