NEWS FEATURE 27 OCTOBER 2020
Can lab-grown brains become conscious?
A handful of experiments are raising questions about whether clumps of cells and disembodied brains could be sentient, and how scientists would know if they were.
tiny structures, known as brain organoids, are grown from human stem cells and have become a familiar fixture in many labs that study the properties of the brain. Muotri, a neuroscientist at the University of California, San Diego (UCSD), has found some unusual ways to deploy his. He has connected organoids to walking robots, modified their genomes with Neanderthal genes, launched them into orbit aboard the International Space Station, and used them as models to develop more human-like artificial-intelligence systems. Like many scientists, Muotri has temporarily pivoted to studying COVID-19, using brain organoids to test how drugs perform against the SARS-CoV-2 coronavirus.
But one experiment has drawn more scrutiny than the others. In August 2019, Muotri’s group published a paper in Cell Stem Cell reporting the creation of human brain organoids that produced coordinated waves of activity, resembling those seen in premature babies1. The waves continued for months before the team shut the experiment down.
This type of brain-wide, coordinated electrical activity is one of the properties of a conscious brain. The team’s finding led ethicists and scientists to raise a host of moral and philosophical questions about whether organoids should be allowed to reach this level of advanced development, whether ‘conscious’ organoids might be entitled to special treatment and rights not afforded to other clumps of cells and the possibility that consciousness could be created from scratch.
The idea of bodiless, self-aware brains was already on the minds of many neuroscientists and bioethicists. Just a few months earlier, a team at Yale University in New Haven, Connecticut, announced that it had at least partially restored life to the brains of pigs that had been killed hours earlier. By removing the brains from the pigs’ skulls and infusing them with a chemical cocktail, the researchers revived the neurons’ cellular functions and their ability to transmit electrical signals2.
Other experiments, such as efforts to add human neurons to mouse brains, are raising questions, with some scientists and ethicists arguing that these experiments should not be allowed.
The studies have set the stage for a debate between those who want to avoid the creation of consciousness and those who see complex organoids as a means to study devastating human diseases. Muotri and many other neuroscientists think that human brain organoids could be the key to understanding uniquely human conditions such as autism and schizophrenia, which are impossible to study in detail in mouse models. To achieve this goal, Muotri says, he and others might need to deliberately create consciousness.
The ethics of experimenting with human brain tissue
Researchers are now calling for a set of guidelines, similar to those used in animal research, to guide the humane use of brain organoids and other experiments that could achieve consciousness. In June, the US National Academies of Sciences, Engineering, and Medicine began a study with the aim of outlining the potential legal and ethical issues associated with brain organoids and human–animal chimaeras.