The origin and nature of conscious experiences - sometimes referred to by the Latin word such as — have been a mystery to us from the earliest antiquity until recently. Many philosophers of consciousness, including modern ones, consider the existence of consciousness to be such an unacceptable contradiction to what they believe is a world of matter and emptiness that they declare it an illusion. In other words, they either deny the existence of qualia in principle, or they claim that they cannot be meaningfully studied by science.
If this judgment were true, this article would be very short. And there would be nothing under the cut. But there is something there...
If consciousness is impossible to comprehend using the tools of science, it would only be necessary to explain why you, I, and almost everyone else are so sure that we have feelings at all. However, a bad tooth caused me a flux. A sophisticated argument to convince me that my pain is illusory will not save me one iota from this torment. I have no sympathy for such a dead-end interpretation of the connection between the soul and the body, therefore, perhaps, I will continue.
Consciousness is everything that you feel (based on information from the sensory organs) and then experience (through perception and comprehension).
A melody stuck in my head, a taste of chocolate dessert, a boring toothache, love for a child, abstract thinking and the understanding that one day all sensations will end.
Scientists are gradually approaching the solution of a mystery that has long worried philosophers. And the culmination of this scientific research is expected - a structured working theory of consciousness. The most striking example of the application of this theory is a full-fledged AI (this does not exclude the possibility of the appearance of AI without a theory of consciousness, but on the basis of already existing empirical approaches in the development of AI)
Most scientists take consciousness for granted and strive to understand its connection with the objective world that science describes. A quarter of a century ago Francis Crick and others decided to put aside the philosophical discussions about consciousness (which have preoccupied scientific men since at least the time of Aristotle) and instead embark on a search for its physical traces.
What exactly in the highly excitable part of the medulla generates consciousness? Knowing this, scientists can hope to get closer to solving a more fundamental problem.
In particular, neuroscientists are looking for neural correlates of consciousness (NCCs) − the smallest neural mechanisms collectively sufficient for any particular conscious experience of sensation.
What must be happening in the brain for you to experience a toothache, for example? Are some nerve cells supposed to vibrate at some magical frequency? Is it necessary to activate some special “neurons of consciousness”? In what areas of the brain could such cells be located?
Neural correlates of consciousness
In the definition of NKS, the clause "minimum" is important. After all, the brain as a whole can be considered the NCS - from day to day it generates sensations. And yet the location can be identified even more precisely. Take the spinal cord, a 46-centimeter flexible tube of nervous tissue inside the spine that contains about a billion nerve cells. If, as a result of an injury, the spinal cord is completely damaged up to the cervical zone, the victim will be paralyzed in the legs, arms and torso, he will not be able to control the intestines and bladder and will be deprived of bodily sensations. Nevertheless, such paralytics continue to experience life in all its diversity: they see, hear, smell, experience emotions and remember just as well as before the tragic incident radically changed their life.
Or take the cerebellum, the “little brain” at the back of the brain. This brain system, one of the oldest in the evolutionary sense, is involved in the control of motor skills, body position and gait, and is also responsible for the deft execution of complex sequences of movements.
Playing the piano, typing on the keyboard, figure skating or rock climbing - all these activities involve the cerebellum. It is equipped with the most famous neurons called Purkinje cells, which have tendrils that billow like coral sea fans and harbor complex electrical dynamics. The cerebellum also contains the largest number of neurons, about 69 billion (mostly star-shaped cerebellar mast cells) - four times morethan the whole brain put together (remember - this is an important point).
What happens to consciousness if a person partially loses his cerebellum as a result of a stroke or under a surgeon's knife?
Yes, almost nothing critical for consciousness!
Patients with this injury complain of several problems, such as less fluent piano playing or less dexterous typing on the keyboard, but never a complete loss of any aspect of their consciousness.
The most detailed study on the impact of cerebellar injury on cognitive function has been extensively studied in the context of . But even in these cases, in addition to coordination-spatial problems (above), only non-critical violations of the executive aspects of management, characterized by , absent-mindedness and a slight decrease in the ability to learn.
The extensive cerebellar apparatus has nothing to do with subjective experiences. Why? An important clue is contained in his neural network - it is extremely uniform and parallel.
The cerebellum is almost entirely a feed-forward circuit: one set of neurons feeds the next, which in turn feeds the third. It has no feedback loops that would resonate back and forth in terms of electrical activity. Moreover, the cerebellum is functionally divided into hundreds, if not more, independent computational modules. Each of them works in parallel, with separate and non-overlapping inputs and outputs that control movements or different motor or cognitive systems. They almost do not interact with each other, while in the case of consciousness, this is another indispensable characteristic.
An important lesson to be drawn from the analysis of the spinal cord and cerebellum is that the genius of consciousness is not born so easily in any place of excitation of the nervous tissue. Something else is needed. This additional factor lies in the gray matter, which makes up the infamous cerebral cortex - its outer surface. All available evidence indicates that sensations are produced by tissue.
It is possible to narrow the area of location of the center of consciousness even more. Take, for example, experiments in which the right and left eyes are exposed to different stimuli. Imagine that the photograph of the Lada Priora is visible only to your left eye, and the photograph of the Tesla S is only visible to your right. It can be assumed that you will see some new car from Lada and Tesla overlays on each other. In fact, for a few seconds you will see Lada, after which he will disappear and Tesla will appear - and then she will disappear, and Lada will appear again. The two pictures will alternate in an endless dance - scientists call this binocular competition, or rivalry of the retinas. The brain receives ambiguous information from the outside, and it cannot decide: is it Lada or Tesla?
If you're lying inside a CT scanner that records brain activity, scientists can detect activity in a wide range of cortical areas, collectively referred to as the "posterior hot zone" (posterior hot zone). These are the parietal, occipital, and temporal regions of the posterior cortex, and they play the most important role in keeping track of what we see.
Interestingly, the primary visual cortex, which receives and transmits information from the eyes, does not reflect what a person sees. A similar division of labor is also observed in the case of hearing and touch: the primary auditory and primary somatosensory cortex do not directly contribute to the content of auditory and somatosensory experience. Conscious perception (including the images of Lada and Tesla) is generated by subsequent stages of processing - in the back hot zone.
It turns out that visual images, sounds and other life sensations originate within the posterior cortex of the brain. As far as neuroscientists can tell, almost all conscious experiences originate there.
Awareness counter
For operations, for example, patients are anesthetized so that they do not move, maintain stable blood pressure, do not experience pain, and subsequently have no traumatic memories. Unfortunately, this is not always possible: every year, hundreds of patients under the influence of anesthesia are conscious to one degree or another.
Another category of patients with severe brain damage as a result of trauma, infections or severe poisoning can exist for years without being able to talk or respond to calls. To prove that they feel life is an extremely difficult task.
Imagine an astronaut lost in the universe listening to mission control's attempts to contact him. A broken radio does not broadcast his voice, which is why the world considers him missing. Something like this would describe the hopeless situation of patients whose damaged brain has deprived them of contact with the world - a kind of extreme form of solitary confinement.
In the early 2000s, Giulio Tononi of the University of Wisconsin-Madison and Marcello Massimini pioneered a method called to determine whether a person is conscious or not.
Scientists applied a coil of sheathed wires to their heads and sent out an electric shock (zap), a strong blast of magnetic energy that caused a short-term electrical current. This excited and inhibited the partner cells of the neurons in the connected regions of the circuit, and the wave resonated through the cerebral cortex until the activity faded.
A network of head-mounted electroencephalogram sensors recorded electrical signals. As the signals gradually spread, their tracks, each corresponding to a specific point under the surface of the skull, were transformed into a movie.
The recordings didn't show any typical algorithm, but they weren't completely random either.
Interestingly, the more predictable the flashing and fading rhythms were, the more likely it was that the brain was unconscious. The scientists measured this assumption by compressing the video data using an algorithm that archives computer files in ZIP format. The compression provided an estimate of the complexity of the brain's response. Volunteers who were conscious had a "perturbation complexity index" of 0,31 to 0,70, with the index falling below 0,31 if they were in deep sleep or under anesthesia.
The team then tested zip and zap on 81 patients who were minimally conscious or insane (in a coma). In the first group, which showed some signs of non-reflexive behavior, the method correctly showed that 36 out of 38 were conscious. Of the 43 patients in the "vegetable" state, with whom relatives at the head of the hospital bed have never been able to establish communication, 34 were classified as unconscious, and nine more were not. Their brains responded similarly to those who were conscious, which meant that they were also conscious, but unable to communicate with their loved ones.
Current research aims to standardize and improve the technique for neurological patients, as well as to extend it to patients in psychiatric and pediatric departments. Over time, scientists will identify a specific set of neural mechanisms that generate experiences.
Ultimately, what we need is a convincing scientific theory of consciousness that will answer the question under what conditions a particular physical system—be it a complex circuit of neurons or silicon transistors—experiences sensations. And why is the quality of experience different? Why does a clear blue sky feel different than the rasp of a badly tuned violin? Do these differences in sensation have any particular function? If so, which one? The theory will allow us to predict which systems will be able to sense something. In the absence of a theory with verifiable predictions, any conclusion about the minds of machines is based solely on our gut instinct, which the history of science has shown to be relied upon with care.
One of the main theories of consciousness is the theory (GWT), put forward by psychologist Bernard Baars and neuroscientists Stanislas Dehan and Jean-Pierre Changeux.
To begin with, they argue that when a person is aware of something, many different areas of the brain get access to this information. Whereas if a person acts unconsciously, the information is localized in the specific sensory-motor system involved (sensory-motor). For example, when you type quickly, you do it automatically. If you are asked how you do it, you will not be able to answer, because you have limited access to this information, which is localized in the neural circuits that connect the eyes with quick finger movements.
Global accessibility generates only one stream of consciousness, since if a process is available to all other processes, then it is available to all of them - everything is connected to everything. This is how the mechanism of suppression of alternative pictures is realized.
Such a theory well explains all sorts of mental disorders, where failures of individual functional centers associated with patterns of neural activity (or an entire area of the brain) introduce distortions into the general flow of the “workspace”, thereby distorting the picture in comparison with the “normal” state (of a healthy person) .
Towards a fundamental theory
The GWT theory claims that consciousness comes from a special type of information processing that has been familiar to us since the dawn of AI, when special programs had access to a small public data store. Any information written on the "bulletin board" became available to a number of auxiliary processes - working memory, language, planning module, recognition of faces, objects, etc. According to this theory, consciousness arises when the incoming sensory information recorded on the board is transmitted into many cognitive systems - and they process data for speech reproduction, storage in memory or performing actions.
Since space on such a bulletin board is limited, we can only have a small amount of information at any given moment. The network of neurons that transmit these messages is presumably located in the frontal and parietal lobes.
Once this sparse (scattered) data is uploaded to the network and made public, the information becomes conscious. That is, the subject is aware of it. Modern machines have not yet reached this level of cognitive complexity, but it is only a matter of time.
The "GWT" theory claims that the computers of the future will be conscious
The General Information Theory of Consciousness (IIT), developed by Tononi and his associates, uses a very different starting point—experiences themselves. Each experience has its own specific key characteristics. It is immanent, exists only for the subject as a "master"; it is structured (the yellow taxi slows down while the brown dog crosses the street); and it is concrete - different from any other conscious experience, like a single frame in a movie. In addition, it is whole and definite. When you sit on a park bench on a warm, clear day and watch children play, the various elements of the experience—the wind blowing your hair, the feeling of joy from the laughter of babies—cannot be separated from each other without the experience ceasing to be what it is.
Tononi postulates that such properties - that is, a certain level of awareness - have any complex and conjugated mechanism, in the structure of which a set of cause-and-effect relationships is encrypted. It will feel like something coming from within.
But if, like the cerebellum, the mechanism lacks complexity and contingency, it will not be aware of anything. As this theory says,
Consciousness is an inherent random ability associated with such complex mechanisms as the human brain.
The theory also derives from the complexity of the underlying interconnected structure a single non-negative number Φ (pronounced “fy”) that quantifies this awareness. If F is equal to zero, the system is not aware of itself at all. Conversely, the larger the number, the greater the inherent random power of the system and the more conscious it is. The brain, which has enormous and highly specific connectivity, has a very high F, and this suggests a high level of awareness. The theory explains various facts: for example, why the cerebellum is not involved in consciousness or why the zip and zap counter really works (the numbers issued by the counter are F in a rough approximation).
The IIT theory predicts that an advanced digital computer-based simulation of the human brain cannot be conscious—even if its speech is indistinguishable from human speech. Just as a simulation of the massive gravitational pull of a black hole does not warp the space-time continuum around the computer using the code, programmed consciousness will never give rise to a conscious computer. Giulio Tononi and Marcello Massimini, Nature 557, S8-S12 (2018)
According to IIT, consciousness cannot be calculated and calculated: it must be built into the structure of the system.
The main task of modern neuroscientists is to use the increasingly sophisticated tools at their disposal in the study of the endless connections of various neurons that make up the brain, to further delineate the neuronal traces of consciousness. Given the confusing structure of the central nervous system, this will take decades. And finally formulate the main theory on the basis of existing fragments. A theory that will explain the main puzzle of our existence: how an organ that weighs 1,36 kg and resembles bean curd in composition embodies the feeling of life.
One of the most interesting applications of this new theory, in my opinion, is the possibility of creating an AI that has consciousness and, most importantly, sensations. Moreover, the fundamental theory of consciousness will allow the development of methods and ways to implement a faster evolution of human cognitive abilities. Man is the future.
Source: habr.com