Whether the cell mass and isolated brain are conscious; How do scientists judge whether they are conscious or not?
Mutori discovered some unusual ways to cultivate human brain organs. He connected brain organs with walking robots, modified the genome of organs with Neanderthal genes, launched it into the orbit of the International Space Station, and used this as a model to develop an artificial intelligence system more similar to human beings.
It is mentioned that they created a human brain organ (1), which can generate coordinated activity waves similar to those seen in premature infants. This wave lasted for several months before the team completed the experiment.
The team's findings have led ethicists and scientists to ask a series of moral and philosophical questions, namely whether organisms should be allowed to reach this level of development, whether "conscious" organisms have the right to special treatment and rights that other cell groups do not have, and whether consciousness can be created by human beings.
Many neuroscientists and bioethicists have an idea that there is no body and a self-conscious brain. Just a few months ago, a team at Yale University in New Haven, Connecticut, announced that they had partially recovered the brain of a pig that was killed a few hours ago. By removing the brain from the pig's skull and injecting chemical mixed reagents, the researchers restored the cellular function of neurons and the ability to transmit telecommunications (2).
Other experiments, such as adding human neurons to the brain of mice, have caused some doubts. Some scientists and ethicists think that these experiments should not be allowed.
These studies have laid the foundation for the debate between those who wish to avoid creating consciousness and those who regard complex organs and organisms as tools to study devastating human diseases. Muotri and many other neuroscientists believe that human brain organs may be the key to understanding unique human diseases such as autism and schizophrenia, which cannot be studied in detail in mouse models. Mutori said that in order to achieve this goal, he and others may need to create consciousness deliberately.
Researchers are now calling for a set of guidelines similar to those used in animal research to guide the humanized use of brain organs and other experiments that can realize consciousness. In June this year, the National Institute of Science, Engineering and Medicine began a study to outline the potential legal and ethical issues related to brain organs.
Concerns about cultivating brains in the laboratory also highlight a blind spot: neuroscientists have no consistent way to define and measure consciousness. Without a workable definition, ethicists worry that they will not be able to stop these experiments before they cross the line.
Some current experiments may magnify this problem. Anil Seth, a cognitive neuroscientist at the university, said that if scientists think that an organism has gained consciousness, they may need to agree on how consciousness is generated. However, he said, if one person's favorite theory holds that the body is conscious and another person's theory holds that it is not, then any confidence that consciousness has appeared will disappear. "Confidence depends largely on what theory we believe. This is a cycle. "
Perceptual state
Creating a conscious system may be much easier than defining it. Researchers and clinicians define consciousness in many different ways for different purposes. Therefore, it is difficult to synthesize them into a concise and practical definition to determine the state of cultivating brains in a laboratory.
Doctors generally evaluate the level of consciousness of vegetative patients according to whether they blink or shrink because of pain or other stimuli. In addition, using electroencephalogram (EEG) readings, researchers can also measure the brain's response to electrical pulses. Compared with the simple and regular activity pattern of the unconscious brain, the conscious brain will show more complex electrical activity.
But this test may not fully explore whether a person lacks consciousness. In the study of brain imaging of comatose or vegetative people, scientists have found that unresponsive people can show some brain activities similar to consciousness-for example, the activities in the motor area when asked to think about walking (3).
During the development of human brain organs, pre-neuron cells (red) become neurons (green) and are connected into a network (white).
In any case, it is difficult for standard conscious medical tests to be applied to brain cells grown in Petri dishes or to completely transform animal brains. When Muotri suggested that the discharge pattern of his organism was as complicated as that seen in premature infants, people didn't know how to deal with this problem. Some researchers believe that the brain activity of premature infants is not complicated enough to be classified as conscious. Organisms, on the other hand, don't blink and don't like the stimulation of pain, so they won't pass the clinical test of consciousness.
In contrast, the whole brain of the recently killed pig is more likely to have the necessary consciousness structure and neural circuits created by the memory and experience of the animal when it is alive. Jeantine Lunshof, a philosopher and neuroethicist at Harvard University in Cambridge, Massachusetts, said, "It is hard to imagine that a brain has been filled with these things." Renshov added: "I don't know what they can do mentally, but they are certainly not empty." Like the Yale team, a certain degree of consciousness may be restored by bringing the dead brain back to life, although scientists have painstakingly used chemical blockers to stop the whole brain from moving.
The researchers agree that they need to take seriously the questions raised by these studies. The meeting of scientists, philosophers and students aims to establish and publish an ethical framework for future experiments. But the paper has been delayed for several months, partly because several authors can't agree on the basic requirements of consciousness.
An increasingly complex theory
Almost all scientists and ethicists believe that so far, no one has created consciousness in the laboratory. But they are all asking themselves what to pay attention to and which theories about consciousness are most relevant. For example, according to a viewpoint called integrated information theory, consciousness is the product of dense connection of whole brain neuron networks. The more interactions between neurons, the higher the level of consciousness-this quantity is called phi. If phi is greater than zero, the organism is considered conscious.
According to this theory, most animals can reach this standard. Christof Koch, of the Allen Institute for Brain Science in Seattle, Washington, thinks that all existing organisms can't reach this threshold, but he admits that more advanced organisms may reach this standard.
Other competitive consciousness theories refer to sensory input or coordinated electrical patterns across multiple brain regions. For example, a view called global workspace theory holds that the prefrontal cortex of the brain is like a computer, processing sensory input and interpreting it, thus forming a sense of existence. Because the organism has no prefrontal cortex and cannot accept input, it cannot become consciousness. "Without input and output, neurons may talk to each other, but this does not represent human thoughts."
However, it may be a fairly simple task to connect a body similar to an organ with an organ. In 20 19, Lancaster's team cultivated human brain organs next to the spinal column and back muscles of mice. When the nerves of human organs are connected to the spine, muscles begin to contract spontaneously.
Madeleine Lancaster, a developmental biologist, studied brain tissue and disorders through the study of similar organs in the laboratory of Cambridge University in England.
Most organoids are formed only to copy a part of the brain-the cortex. However, if human stem cells develop long enough and have the right growth factors, they will spontaneously rebuild many different parts of the brain, and then these parts will begin to coordinate their electrical activities. In a study published on 20 17, Paola Arlotta, a molecular biologist at Harvard University, induced stem cells to develop into brain organs composed of many different cell types, including photoreceptor cells found in the retina. When exposed to light, neurons in the organ-like body begin to discharge. But the fact that these cells are active does not mean that these organs can see and process visual information, Arlotta said. This simply means that they can form the necessary circuits.
Arrota and Lancaster think that their organs are too primitive to produce consciousness because they lack the necessary anatomical structure to create complex EEG patterns. Nevertheless, Lancaster admits that for higher organs, it depends on its definition. She said: "If you think a fly is conscious, then the organs may also be conscious."
However, Lancaster and most other researchers believe that things like activated pig brains are more likely to gain consciousness than organs. The team studying pig brain, led by neuroscientist Nenad sestan, tried to find a new way to restore organ vitality instead of creating consciousness. Researchers can activate a single neuron or a group of neurons and be careful to avoid generating a wide range of brain waves. However, when sestan's team saw similar coordinated EEG activity in one of the brains, they immediately stopped the project. Even after neurologists confirmed that this pattern was inconsistent with consciousness, the research team still used brain anesthesia as a preventive measure.
Sestan also contacted the National Institutes of Health (NIH) for guidance on how to proceed. The agency's neuroethics team, including Renshoff and Insoo Hyun of Case Western University in Cleveland, Ohio, evaluated the work and agreed that sestan should continue to anesthetize the brain. However, the organization did not make more general regulations, nor did it routinely require bioethical evaluation of suggestions for similar organs, because its members thought that consciousness was unlikely to appear. Nor does the National Institutes of Health define consciousness. Hyun said, "It's very flexible. Everyone has his own meaning." "If it is not clear that we are talking about the same thing, this is a big problem."
Fuzzy definition
Some people think that even trying to identify consciousness in any kind of brain preserved in the laboratory is futile. "Since we don't understand consciousness, he started some awareness of imaging and taking measures when people were in a vegetative state." We should not be too arrogant. He said that further research should be carried out with great caution.
Laureys and others pointed out that the experience of similar organs may be very different from that of premature infants, adults or pigs, and cannot be directly compared. In addition, the structure of the simulation device may be too small to accurately measure their activities, and the similarity between the simulation device and the EEG pattern of premature infants may be just a coincidence. Other scientists who study brain-like organs also agree with Laureys that the question of whether the system is conscious cannot be answered. Many people completely avoid this idea. "I don't know why we ask this question, because this system is not a human brain." They are composed of neurons, which are electrically active, but we should carefully consider how to compare them. "
Muotri hopes that his organ-like system can rival the human brain in at least some aspects, so that he can study human diseases and find a cure. His motivation is personal: his 14-year-old son suffers from epilepsy and autism. "He fought against life," Mutori said. Brain-like organs are a promising way because they reproduce the earliest stage of brain connection, which cannot be studied during the development of human embryos. But he said that studying human brain diseases without a fully functional brain is like studying a pancreas that can't produce insulin. "To this end, I need a brain organ model that really looks like a human brain. I may need a conscious organ.
Mutori said that he didn't know what definition to use to determine whether a quasi-organ reached consciousness. He said that to some extent, organs similar to organs can even help researchers answer the question of how the brain produces a state of consciousness. Develop an algorithm to describe how the brain produces consciousness. His project is partly funded by Microsoft, and its goal is to create an artificial system that works like human consciousness.
At present, there are no laws and regulations in the United States and Europe that can prevent researchers from creating consciousness. The team of the National Academy of Sciences plans to release a report early next year, summarizing the latest research and judging whether it is necessary to formulate relevant laws and regulations. Members plan to express their opinions on some issues, such as whether people's consent is needed to develop their cells into brain-like organs, and how to study and treat them humanely. The International Society for Stem Cell Research is also studying the guide to organs, but it doesn't mention consciousness because it thinks that science hasn't done this yet.
Hyun said that the neuroethics team at the National Institutes of Health has not seen any suggestions on creating complex and conscious organ-like bodies, which will require new guidelines. Muotri said that he didn't know anyone who was deliberately trying to create conscious quasi-organs, although according to some definitions, a sufficiently complex quasi-organ might unexpectedly reach this state.
However, Mutori and others say they welcome some guidelines. This may include asking scientists to prove the number of human brain organs they use, using them only for research that cannot be carried out in any other way, limiting the pain that may be imposed on them, and treating them humanely.
Making such suggestions in advance will help researchers weigh the costs and benefits of creating conscious entities. Many researchers emphasize that such experiments may produce important insights. Lancaster said: "There are some truly conscious people who suffer from neurological disorders, but there is no treatment." "If we really stop all research because of this philosophical thinking experiment," she added, "it will be very bad news for people who really need some new treatments."
However, this treatment can still be tested in brain organs and tissues made of mouse stem cells or in conventional animal models. Such experiments can also provide information for ethical discussions about the use of human organs. For example, Hyun wants to see researchers compare the EEG patterns of rat brain organs with those of living brain organs, which may show how effective human organs are in replicating human brains.
In Mutori's view, there is no difference between studying human organs and tissues and experimental mice. "The animal model we use is conscious and there is no problem," he said. "We need to move forward. If it turns out that they are conscious, to be honest, I think it's no big deal. "