The discovery offers an explanation for the phenomena of optical illusions related to wrong discrimination of movement
Illustration: The Weizmann Institute When Clint Eastwood disassembled a gun, the area responsible for the sense of touch "turned on" in all brains
By Marit Sloin, Haaretz
The brain / MRI scanning of subjects while watching a movie indicates a great uniformity in the brain activity of different people
The classic Western "The Good, the Bad and the Ugly" stars in a new Israeli study, which wanted to check what goes on in a person's mind when they watch a movie. The study, conducted by Prof. Raphael Malach from the Department of Neurobiology at the Weizmann Institute together with research student Uri Hasson, is unusual in its methodology. "All brain imaging studies in humans are done under controlled laboratory conditions," says Malach. "The person focuses his gaze on the images that are presented to him one by one and at the same time maps in his mind the areas of the brain that react to the sight of the images. But the world is dynamic - many things happen in it at once, in an unceasing flow. The question of what happens in a person's mind when exposed to such an environment full of stimuli has not been examined yet. We decided to create such an environment, and the way to do it was to screen a motion picture. When exposed to a film, the sensory system is intensively exposed to objects, sounds, colors and more. We decided to show the viewers-the subjects an action movie, which should captivate all the senses in a more distinct way than any other movie."
The group of researchers from the Weizmann Institute chose the movie "The Good, the Bad and the Ugly" starring Clint Eastwood. They showed volunteers a 30-minute clip of the film and examined what was going on in their brains using a functional magnetic resonance imaging (fMRI) system. The results yielded two surprises. It turned out that in all subjects the film evoked surprisingly similar brain responses. "Everyone's brain worked the same way while watching the movie," says Malach. "We expected to see differences arising from the personality of each individual, but this is not what we saw. It became clear to us that despite the rich amount of information that flowed to the viewers of the film, their brains 'ticked' in surprising harmony. In other words, despite the uniqueness of different people, it turns out that there is a great compatibility between people. In a certain sense, it can be said that when we are exposed to the same visual environment, the brains of all of us 'tick' together in synchronized patterns in time and space."
In addition to the discovery of uniform brain activity, the study provided a second surprise. Hasson and Malach discovered that different areas of the brain pick up from the motion picture the images and scenes suitable for their specialization and operate independently, ignoring other visual elements that activate other areas of the brain. A certain area "takes command", and at the same time other areas are silent. The viewer does feel that he is watching a uniform and continuous film, but in fact each area of his mind "sees" its own private and unique film. "In laboratory conditions this is expected, because the tasks are focused on certain functions", says Malach. "On the other hand, in a natural situation, where a wealth of images appear at once, we do not see each detail separately, but rather one flowing experience. Despite this, we see in the fMRI mapping that at every moment in the film certain areas are active and others are silent."
Prof. Malach's son, Eran, built a computer program that makes it possible to link each moment when strong activity was detected in certain brain areas and the scene in the movie that triggered this activity. The software cuts sections from the film and builds a clip consisting of all the sections that activated a certain area. This is how it turned out, for example, that the area of the brain specializing in facial recognition was activated only when close-up images of the actors' faces appeared on the screen. "When we looked at the clip, we saw that every time the director focused attention on the faces, the same area was activated," says Malach. "Near this area there is an area that, according to information, specializes in identifying places. The clip we made showed that this area was only activated when images of landscapes and buildings were projected on the screen. And so, even though you experience a continuous movie, the areas of the brain work like an orchestra. Each time a different instrument takes over, as if they let it play solo at that moment."
Malach calls the methodology used by the researchers "inverted matching" - instead of the classic form of research, where you give a stimulus and measure a response, here you take the response and use it to find out what the stimulus was. Thus, the use of motion picture allowed scientists to effectively discover the functional specializations of many different areas of the brain. The researchers were surprised, for example, to find that an area of the brain known to be specialized for the sense of touch was activated when scenes involving subtle hand movements, such as disassembling and assembling a gun, were shown. Malach thinks that this interesting connection between the sense of touch and seeing hand movements suggests a brain system related to imitation and motor learning.
"We found activity in many areas where it is not known what they are responsible for," says Malach. "Using our method we can find in the film what activates them, and from there find out what functions they fulfill in brain activity. The method allows you to select any area that seems interesting and see what activates it in the film." Hasson and Malach's research may allow researchers to locate areas in the brain responsible for cognitive and mental problems, vision problems, and more. "Since the activity measured by fMRI while watching movies is very similar from person to person, using the method will make it possible to compare the brain image of healthy people with that of people suffering from brain pathology. We have already started to test this in autistic people, and while watching the film we found in them a brain picture that is completely different from that of normal people", says Malach.
The scientists of the Weizmann Institute revealed the way in which the long-term implementation of "microprocessors" in the brain is carried out
26/3/04
A well-known visual trick occurs when we look at a square, which suddenly changes into an elongated rectangle. In practice, the square is erased and the rectangle appears, but it seems to us that the square gradually lengthens until it becomes a rectangle.
Why is this happening? What does this say about the brain's ability to analyze, process and understand reality as it should, according to the data that is transmitted to it from the sensory organs, such as the eye? Prof. Amiram Greenold from the Department of Neurobiology at the Weizmann Institute of Science, recently discovered what causes the brain to make a mistake in understanding the reality of the square alternating with the rectangle. This finding, which has far-reaching implications for the brain's data processing strategies, was published today in the scientific journal Nature.
This research is a milestone in the ongoing scientific effort to decipher the brain's neural code, something that will make it possible to understand the unknown operating principles of the brain's "operating system". Prof. Greenold says that deciphering the neural code will lead to a leap forward in brain research, similar to the rapid development that occurred in molecular biology following the decoding of the genetic code. The optical imaging also contributes to the development of a new era in the field of medicine.
In the past, Prof. Grinold discovered that cell groups that process different data in the brain are organized in fixed geometric contexts, that is, that the processing of information in the brain is based on a geometric-modular division of defined cell groups, which repeats itself over and over again. Thus, for example, a group of cells engaged in a unique task creates a characteristic spatial structure, which integrates - while maintaining a fixed geometric relationship - into another structure, created by another group of cells, which handles the processing of other parts of the information. For example, when the brain receives visual information, the groups of cells that process the depth dimension fit together like a kind of Lego game blocks, or join (puzzle) groups of cells that deal with color processing, and other groups of cells that process the shape data.
The precise geometric-modular combination, repeated over and over again, of all these "joining" components, creates in the brain a sort of massive array of "microprocessors" identical in structure and shape. Such processors cover the entire field of vision, breaking down the image into its various components (depth, movement,
color and other visual features), process each feature separately and then build, the perception of vision in superior areas of the brain.
This discovery, as well as other discoveries, were made using a unique optical imaging system developed by Prof. Greenold. The system is based on a fast and extremely sensitive camera and a series of colors developed in Grinold's laboratory by the chemist Dr. Rina Hildesheim. These dyes, which adhere to the membrane of living brain cells, change the intensity of their illumination (fluorescence) according to the level of activity of the cells. The high-speed camera is able to notice these color changes, and thus the researchers can know which cell "fires" an electrical nerve signal, and when exactly it does so. The main advantage of this viewing method is that it allows the electrical activity of millions of cells to be recorded together, in real time, instead of tracking each individual nerve cell using an electrical contact (electrode). Processing the data collected in this system allows researchers to accurately map the activity of the functional arrays of the neural networks in the brain.
Another important feature of the system and method developed by Prof. Greenold is that it makes it possible to distinguish the activities of the nerve cells in the brain even when they are engaged in the "priming" of sending nerve signals. In other words, the system is not limited to a narrow two-dimensional distinction between a cell that "fires" a neural signal (a suprathreshold signal) and a cell that does not "fire" (a subthreshold state), but is able to distinguish many intermediate states that occur below the signal's firing threshold the nervous This ability allowed Prof. Greenold and the members of the research group he heads to identify different states of cells, each of which lacks a different amount of activity to reach the threshold from which the cell "fires" and sends an electrical nerve signal to its members in the network. This is how they were able to remap the groups of cells responsible for analyzing the data of various visual phenomena (vertical movement, horizontal movement, color, etc.).
Here we can return to the visual trick we started with. What makes the brain "think" that the eye has observed a movement event, that the square gradually lengthens and turns into a rectangle? The researchers noticed a graded threshold that the image of the square creates in the cerebral cortex, which means that the distance to the critical threshold (for sending nerve signals) gradually increases, as you move away from the place of supraspinal activity of the square itself. With the appearance of the elongated rectangle, another activity appears that crosses the threshold
Gradually, as you move away from the initial focus. Therefore an illusion of movement is created. In which processing unit in the brain, exactly, does this "failure" in processing information take place? Many scientists believed that the processing of the movement feature was done in a group of cells located in the "depth" of the visual data processing system in the brain, in which no less than 36 processing stations have been discovered working one after the other. But thanks to the unique optical imaging method developed by Prof. Grinold, he was able to discover that this processing station is located precisely in one of the first layers of the data processing array in the brain. To directly view the film showing both the optical illusion and the results of the optical imaging see at this link.
----
His research in the field of brain research earned Prof. Grinold, recently, the Dan David Prize which will soon be awarded to him in the capacity of the President of the State, Moshe Katsav. Prof. Greenold is the first Israeli to win this prestigious international award. The Dan David Prize, administered by Tel Aviv University, is given for outstanding excellence and many achievements, originality, creativity, breaking through fields, contribution to humanity and in the field of brain research, dozens of candidates from 17 countries competed for it. The award's steering committee includes, among others, Prof. Itamar Rabinovitch, president of Tel Aviv University, Dr. Bruce Alberts, president of the US National Academy of Sciences, Prof. Yehoshua Yurtner, former president of the Israel Academy of Sciences, and Dr. Henry Kissinger, former Secretary of State of the United States.
