The progress of science has meant that today almost all vital organs can be routinely transplanted, except for one: the brain. Given that the mind resides there and that, therefore, it is not simply an interchangeable piece—but what actually defines the person—it is evident that the preservation of the brain beyond death, its copying or its re-creation, all give rise to multiple questions and debates. But when dealing with what some consider the most complex object in the universe, the technological challenges are so immense that any ethical discussion often seems superfluous. However, some recent advances suggest that the possibility of simulating or preserving the human brain is no longer a mix between transhumanism and science fiction, but the emerging science of the 21st century.
Last March, neuroscientist Nenad Sestan from Yale University presented at a meeting of the National Institutes of Health of the USA a technique called BrainEx, which has managed to keep the brains of pigs alive for 36 hours after their removal from the body. Although Sestan prefers not to comment on the study because it is in the process of being published, MIT Technology Review explained that the method uses a pumping system and artificial blood to keep the brain nourished and oxygenated, and that the researcher described his results as “mind-boggling.” And although there is no indication that the brains of pigs maintain consciousness—it would be something like a coma—Sestan said the procedure could work for other species, including primates.
After Sestan’s announcement, the researcher and 16 other neuroscientists and bioethicists published an article in Nature last April in which they reflected on the implications of experimentation with human brain tissue. Experts agree that some of the proclamations disseminated in the media today are mere fantasy. Among them stands out the plan of the Italian neurosurgeon Sergio Canavero to transplant human heads, something that neuropsychiatrist Steven Hyman of the Broad Institute in Cambridge, Massachusetts told MIT Technology Review, “is not remotely possible.”
Transfer the mind to the computer
Other equally daring proposals are making headway, at least among a part of the scientific community. On the Janelia Research Campus, an institution of the Howard Hughes Medical Institute (USA) dedicated to cutting-edge research in neurobiology, Kenneth Hayworth is searching for the technique to preserve the brain beyond death and record all its connections to store them in digital form, in what would be equivalent to a transfer of the mind to the computer. The Brain Preservation Foundation chaired by Hayworth has recently awarded a prize to Nectome, a company founded by two graduates of the Massachusetts Institute of Technology (MIT) that aims to vitrify human brains with a view to the future digitalization of their contents, including their memories and, who knows, maybe their consciousness.
Nevertheless, efforts such as those of Hayworth and Nectome have provoked scepticism and rejection among other neuroscientists. Shortly after the announcement of the collaboration of Nectome with Edward Boyden, director of the Synthetic Neurobiology group of the MIT Media Lab, the institution decided to sever links with the company. “We no longer work with Nectome,” confirms Boyden to OpenMind. The break is based on the claim of Nectome to preserve still-living brains in patients, but also because “neuroscience has not sufficiently advanced to the point where we know whether any brain preservation method is powerful enough to preserve all the different kinds of biomolecules related to memory and the mind,” and that “it is also not known whether it will be possible to recreate a person’s consciousness.”
In fact, although a current trend favours the idea that we are simply the set of our neural connections (or connectome), not all experts support the hypothesis that our mind is limited to a high-resolution fixed picture of the brain structure. Hongjun Song, a neuroscientist at the University of Pennsylvania (USA) and one of the signatories of the Nature article on experimenting with human brains, tells OpenMind that: “My current view is that knowing the hardware, all the brain connections, will not be sufficient. We need to know the software as well, how our brain computes the information.”
Apart from these controversial projects, other lines of research are yielding spectacular advances, such as that of organoids or mini-brains. In this case, it is a bottom-up approach: using stem cells to generate neurons that interconnect with each other in structures that do not exceed the size of a grain of rice, but are capable of functioning as small-scale brains. Recently it has been possible to grow human mini-brains that create their own blood vessels. According to what Ben Waldau, director of this study and neurosurgeon at the University of California at Davis (USA), has told OpenMind, “the field will likely move towards generating parts of brains such as a motor cortex for transplantations. Vascularization may allow us to grow bigger grafts and have better survival after transplantation.”
This technology continues to surprise: researchers have also recently managed to transplant human mini-brains into the brains of live mice, and a project of the Max Planck Institute (Germany) aims to produce brain organoids with genes from our extinct ancestor, the Neanderthal. “There is tremendous progress in the field of brain organoids,” says Song, whose research covers this field.
The three-dimensional nature of the minibrains allows for more realistic experiments than a two-dimensional structure would. Credit: Hoffman-Kim Lab/Brown University
The main interest of the mini-brains is to offer a new experimental model to study the development and diseases of the brain, in addition to replacing laboratory animals in the trials of treatments and drugs. But to what degree can the simulation of the human brain reach in these organoids? One of the pioneers of this technology, Thomas Hartung, has said that the neuronal activity present in mini-brains, even if it is only something mechanical, amounts to “a primitive type of thinking.”
“We are making progress to generate organoids with functional neuronal connections and circuits,” summarizes Song, suggesting that these tissues may be able to function as small biological computers: “I think it will be possible to train the circuit to perform simple tasks.” But beyond this, on whether one day we will be able to build something similar to a human brain in vitro, an abyss opens up on which placing any bet would be too risky. “We do not have a clear idea what consciousness is, so we will not know the answer to that,” Song concludes.