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Jan 10, 2021
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Experiments on humans: how the human brain is examined

It is extremely difficult to recognize in this system, which has cosmic numerical parameters and is in constant motion, mechanisms that could be correlated with what we call memory and thinking. Sometimes for this you have to penetrate directly into the brain. In the most direct physical sense.

Whatever the defenders of wildlife may say, so far no one has forbidden researchers to experiment on the brain of monkeys and rats. However, when it comes to the human brain – a living brain, of course – experiments on it are practically impossible for reasons of law and ethics. You can get inside the “gray matter” only, as they say, for the company with medicine.

Brain research

One of those chances given to brain researchers was the need for surgical treatment of severe cases of epilepsy that do not respond to drug therapy. The cause of the disease is the affected areas of the median temporal lobe. It is these areas that need to be removed using neurosurgery methods, but first of all they need to be identified so that, so to speak, not to “cut off the excess”.

American neurosurgeon Yitzhak Fried from the University of California (Los Angeles) was one of the first to apply the technology of inserting 1 mm electrodes directly into the cerebral cortex in the 1970s. Compared to the size of nerve cells, the electrodes had cyclopean dimensions, but even such a crude instrument was enough to remove the average electrical signal from a number of neurons (from a thousand to a million). In principle, this was enough to achieve purely medical goals, but at some stage it was decided to improve the instrument. From now on, the millimeter electrode received an end in the form of a branching of eight thinner electrodes with a diameter of 50 μm. This made it possible to increase the measurement accuracy up to the fixation of the signal from relatively small groups of neurons. Methods have also been developed to filter out the signal sent by a single nerve cell in the brain from the “collective” noise. All this was done not for medical purposes, but for purely scientific purposes.

What is brain plasticity?

The plasticity of the brain is the amazing ability of our organ of thinking to adapt to changing circumstances. If we learn a skill and train the brain intensively, a thickening appears in the area of ​​the brain responsible for that skill. The neurons located there create additional connections, consolidating the newly acquired skills. In the event of damage to a vital part of the brain, the brain sometimes re-develops the lost centers in the intact area.

Named neurons

The objects of research were people who were awaiting surgery for epilepsy: while electrodes embedded in the cerebral cortex were reading signals from neurons to accurately determine the area of ​​surgical intervention, very interesting experiments were carried out along the way. And this was the very case when the icons of pop culture – Hollywood stars, whose images are easily recognizable by the majority of the world’s population, brought real benefits to science. Yitzhak Frida’s co-worker, physician and neurophysiologist Rodrigo Kian Quiroga, showed subjects on his laptop a selection of well-known visuals, including popular personalities and famous buildings such as the Sydney Opera House. When these pictures were shown, the electrical activity of individual neurons was observed in the brain, and different images “turned on” different nerve cells. For example, a “Jennifer Aniston neuron” was installed, which “fired” every time a portrait of this romantic actress appeared on the screen. Whatever photo Aniston was shown to the subject, the neuron “her name” did not fail. Moreover, it also worked when frames from the famous series in which the actress starred appeared on the screen, even if she was not in the frame herself. But at the sight of girls who only looked like Jennifer, the neuron was silent.

Brain research

The studied nerve cell, as it turned out, was associated precisely with the holistic image of a particular actress, and not at all with individual elements of her appearance or clothing. And this discovery provided, if not a key, then a clue to understanding the mechanisms of long-term memory retention in the human brain. The only thing that prevented us from moving forward was the very considerations of ethics and law, which were mentioned above. Scientists could not place electrodes in any other areas of the brain, except those that were subjected to preoperative research, and the study itself had a limited medical time frame. This made it very difficult to find an answer to the question of whether the neuron of Jennifer Aniston, or Brad Pitt, or the Eiffel Tower really exists, or maybe as a result of measurements, scientists accidentally stumbled upon only one cell from a whole network connected with each other by synaptic connections, which is responsible for preserving or recognition of a certain image.

Playing with pictures

Be that as it may, the experiments continued, and Moran Cerf joined them – an extremely versatile personality. Israeli by birth, he tried himself as a business consultant, hacker and at the same time a computer security instructor, as well as an artist and comic book writer, writer and musician. It was this man with a spectrum of talents worthy of the Renaissance who undertook to create a kind of neuromachine interface on the basis of the Jennifer Aniston neuron and others like him. This time, 12 patients of the Medical Center named after V.I. Ronald Reagan at the University of California. In the course of preoperative studies, 64 individual electrodes were inserted into the region of the median temporal lobe. In parallel, experiments began.

Brain research

The development of the sciences of higher nervous activity promises incredible prospects: people will be able to better understand themselves and cope with now incurable ailments. The problem is the moral and legal side of experiments on a living human brain.

First, these people were shown 110 images of pop culture themes. As a result of this first round, four pictures were selected, at the sight of which the excitation of neurons in different parts of the studied area of ​​the cortex was clearly recorded in the entire dozen subjects. Then, two images were displayed simultaneously on the screen, superimposed on each other, and each had 50% transparency, that is, the images were shown through each other. The subject was asked to mentally increase the brightness of one of the two images, so that he obscured his “rival”. At the same time, the neuron responsible for the image on which the patient’s attention was focused produced a stronger electrical signal than the neuron associated with the second image. The pulses were fixed by electrodes, entered the decoder and turned into a signal that controls the brightness (or transparency) of the image. Thus, the work of thought was quite enough for one picture to start “hammering” another. When the subjects were asked not to intensify, but, on the contrary, to make one of the two images paler, the brain-computer link again worked.

Light head

Was this exciting game worth the need to conduct experiments on living people, especially those with serious health problems? According to the authors of the project, it was worth it, because the researchers not only satisfied their scientific interests of a fundamental nature, but also groped for approaches to solving quite applied problems. If there are neurons (or bundles of neurons) in the brain that are excited at the sight of Jennifer Aniston, then there must also be brain cells responsible for concepts and images that are more essential for life. In cases where the patient is unable to speak or signal his problems and needs with gestures, direct connection to the brain will help doctors learn about the patient’s needs from neurons. Moreover, the more associations are established, the more a person can communicate about himself.

Brain research

However, an electrode embedded in the brain, even if it is 50 microns in diameter, is too crude a tool to accurately address a specific neuron. A more subtle method of interaction is optogenetics, which involves the transformation of nerve cells at the genetic level. Ed Boyden and Karl Thessot, who began their work at Stanford University, are considered to be among the pioneers of this direction. Their idea was to affect neurons using miniature light sources. For this, the cells, of course, must be made light-sensitive. Since the physical manipulations of transplanting light-sensitive proteins – opsins – into individual cells are almost impossible, the researchers suggested … infecting neurons with a virus. It is this virus that will introduce a gene that synthesizes a light-sensitive protein into the genome of cells.

This technology has several potential uses. One of them is the partial restoration of vision in an eye with a damaged retina by imparting light-sensitive properties to the remaining non-light-sensitive cells (there are successful experiments on animals). Receiving electrical signals triggered by the incident light, the brain will soon learn to work with them and interpret them as images, albeit of inferior quality. Another application is working with neurons directly in the brain using miniature light guides. By activating different neurons in the brain of animals with the help of a beam of light, it is possible to trace what behavioral responses these neurons cause. In addition, “light” intervention in the brain may have therapeutic value in the future.

Oleg Makarov



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