The story that enters the brain: what happens in the head during communication between people

Prof. Uri Hasson, Princeton: The brain of the listener listening to the story becomes very similar to the brain of the narrator while she is telling the story

The human mind is probably the most amazing machine that exists. Like the brain of animals, it is capable of rapidly translating a multitude of physical and chemical stimuli into assembling a detailed world picture. On top of that, he is able to recall in the blink of an eye memories of events that happened years ago or seconds ago and also make long-term plans and predict future events. He deciphered events that happened millions of years ago and built spaceships that fly billions of kilometers away. The human mind wrote wonderful musical compositions, devised the theory of relativity, deciphered the structure of matter and found cures for many diseases. In only one area of ​​research, he was left far behind - his own research. Compared to other fields of knowledge, the human mind is still a largely unknown land. Researchers are already familiar with the anatomy of the brain, which can also be studied in cadavers, but still only know very little about the processes that take place in the brain of a living person. With the limited tools available to science, it is possible to get a very general idea of ​​the activity of the brain. For example, we roughly know which areas are responsible for the various functions, such as learning, face recognition or speech, but our understanding is still very little about the mechanisms of action of brain functions such as memory, information processing or emotions, not to mention what goes wrong in the brain in a very long series of disorders, from schizophrenia to autism.

complex and deep

The brain is a tangled tissue of tens of billions of nerve cells. The cells have a tree-like part, each of whose branches can connect to another cell, so that each cell can form an information network with hundreds or even thousands of other cells. The number of connections between brain cells is estimated at more than 100 trillion (one million millions), and the level of complexity of the system is almost unimaginable. When a brain cell works, it produces an electrical signal, or a certain sequence of signals, which are transmitted to the other cells, by electrical or chemical means.
One way to try to understand how the brain works is to measure the electrical activity. Already in the 19th century, researchers discovered that it is possible to measure waves outside the brain that reflect its electrical activity. Over the years, the measurement has been refined and several types of waves have been characterized, but this method, known as EEG (ElectroEncephaloGram) has some notable limitations. First, it is very insensitive, and only very large areas of the brain can be characterized with it. Secondly, it naturally mainly reflects what happens in the more external areas of the brain, and not in the more internal parts, or in areas whose direction in relation to the skull does not allow effective measurement of the waves. A more advanced development of the method, including sticking electrical electrodes into the brain to measure the electrical activity in certain areas. This method is much more precise and sensitive, but the electrodes are very thin, still large in relation to the brain cells, and are able at best to measure the activity of thousands of cells, not single cells. This method also involves a certain methodological difficulty: the brain of most people shows a certain reluctance to the idea of ​​having electrodes ignited in it. Even if this reluctance is overcome, there is a fear that the very act of sticking the electrode will damage a certain area, or affect its function, so the ability to use this method for research is very limited. And there is another fundamental problem in the study of the brain: the scientists are trying to understand how it really works, but a situation in which a person wears a helmet to measure waves, or electrodes are stuck in their head, does not really reflect the reality of most people: the very unnatural situation already greatly impairs the researchers' ability to try to understand In these methods the normal activity of the brain.

to observe from the outside

One of the developments that gave a real boost to brain research is the fMRI. Since the human body consists mostly of water, which is hydrogen and oxygen, it has a tremendous abundance of hydrogen atoms. In a natural state, these atoms rotate around themselves freely. However, when you put them between magnets, they align in front of the magnetic field. If radiation is applied to them perpendicular to the direction of the field, for example radio waves, it causes them to change direction, and in the process emit energy. This emission can be measured using detectors, cross each measurement with the intensity of the radiation, and create a map of the nuclei with the help of a computer - that is, find out where there is more water, and where there is less. Since each type of tissue (blood, muscle, fat, etc.) contains different concentrations of water, it is possible to create an image of the soft tissues with this method, without penetrating the body, and without using harmful radiation (radio waves are relatively weak radiation, and not dangerous). Later, the device was refined so that the magnet rotates around the subject and makes it possible to photograph sections or layers of the body, and to assemble (with the help of a computer, of course) a detailed two-dimensional or three-dimensional image. Such devices are called MRI (Magnetic Resonance Imaging), and they have become a central tool in medical diagnosis, especially of what is happening in the brain. In the last two decades, functional MRI, or fMRI for short, came into the world. Here, a system that measures the concentration of oxygen atoms, mainly in the hemoglobin molecules, which carry the oxygen in the red blood cells, was added to the normal imaging system. This device is therefore able to measure where in the brain there is increased blood flow, which indirectly indicates increased electrical activity. The fMRI is also very far from accurate at the cellular level, but its ability to measure activity inside the brain, even in the deep layers, without the need for penetration and while the subject is able to function almost without interruption, has boosted the scientists' ability to study the intricacies of the brain.

Coupling and understanding

Even with the improvement in the ability to measure, the brain is still an extremely complex system, in which it is very difficult to isolate certain variables and test only them. Therefore, most researchers have so far preferred relatively simple experiments, hoping to decipher basic operations first. For example, the function is measured while the subject sees a picture of a cat, or utters the word cat, and checks which areas of the brain react. Therefore, although it is a subject who is conscious and functioning properly, the test is very far from what happens in the real world.

To examine a more realistic situation, a research group in the Department of Psychology and Brain Research at Princeton University decided to examine what happens in the brain while a person tells a story. Research student Lauren Silbert entered an fMRI machine, and recorded herself telling about her day's events, while the researchers, led by Prof. Uri Hasson, examine brain function. The result was surprising. Previously, the researchers thought that in such a situation only a limited area of ​​the left brain would be activated, mainly the area responsible for the motor function of the vocal cords. "We discovered that a much wider neural network is activated, on both sides of the brain, which includes areas related to language and many other functions," says Hasson. In the next step, the researchers checked what happens in the brain of a person who hears Lauren's story: they played the recordings to other subjects who were lying in the fMRI machine, and measured their brain functions. After that, the subjects were asked questions about the content of the story, to check how well they understood it. "We discovered to our surprise that the brain of the listener listening to the story became very similar to the mind of the narrator while she was telling the story. That is, the same areas start operating at the same times," Hasson explains. "There is a kind of coupling of the brains, and we saw that the stronger this coupling, the better the listener understood the story."

A wide research field

The study by Hasson and his colleagues was published this week in the American Academy of Sciences, PNAS (link to the research article - at the bottom of the page). Since it deals with real stimuli, and in a situation that is relatively close to reality, it may have far-reaching consequences, even though for now it is only basic science, and not applied research. "It is possible, for example, to measure with our method how well a teacher succeeds in conveying the material to his students, or how much a political speech affects the audience it is intended for," Hasson says. "In addition to that, we can check situations of lack of communication, and try to check what causes this failure." Another application of the experimental system may be in the understanding of clinical disorders such as autism, which are manifested by impairment of the patient's brain's ability to communicate with other brains.

"Until now, we were basically investigating a monologue situation," says Hasson. "One person speaks and one listens. In the next step we want to test a more real situation, of dialogue, a person who both speaks and listens. We have two MRI machines connected to each other, and we want to test such situations and measure what happens in the subjects' brains." In the coming years Hason intends to deepen the research in other directions. "We want to investigate the processes of dynamics between minds, what causes better or less understanding, communication disorders and clinical disorders", he concludes. "There is an extensive field of research here that will occupy us and the research groups that will join us for many years to come."

To the article on Itai Nebo's blog "The Little Light" - Pressing the speaker button will allow you to listen to the interview with Prof. Hasson on the program "Microscope"

The research paper in the journal PNAS

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