Human Consciousness: What Are the Ethics of Experimenting with Brain Tissue?

One of the most exciting scientific developments of recent years has been the development of relatively advanced human brain surrogates, which are enabling researchers to understand more about a host of neurological disorders

This avenue of research is incredibly exciting as it provides scientists with a much more accurate representation of brain function than studying the brains of animals. Often, a significant number of treatments that are developed in animals fail to work in people.

However, like many groundbreaking scientific developments, these new approaches raise a number of ethical issues that need to be considered, especially as these surrogates become more and more similar to real human brains.

In light of this, an interdisciplinary group of researchers—including biologists, philosophers and ethicists—has outlined the issues surrounding experimentation on human brain surrogates in a new comment article published in the journal Nature.

"It's incredibly important that the research be able to go forward in order to alleviate a tremendous amount of human suffering that arises from injury to the human brain," Nita A. Farahany, a leading expert on the ethical, legal and social implications of biosciences, told Newsweek. "But some of the questions about how to ethically make progress in this area, include asking some difficult questions."

For example, what if these brain surrogates appeared to display semblances of consciousness or sentience? Would they deserve special protections, like those afforded to human or animal research subjects?

Currently, there are three main classes of brain surrogates that offer researchers a way to investigate how the living brain works, "without the need for potentially risky—if not ethically impossible—procedures in people," the authors wrote in the article.

These three approaches are "organoids", "ex vivo brain tissue" and "chimaeras."

Brain organoids are 3D multicellular structures, which are essentially like lab-grown 'mini-brains'. Scientists use stem cells—which can develop into any type of cell—to grow structures that resemble certain regions of the human brain and mimic their basic features.

"These are tiny, on the order of two or three million cells, compared to around 86 billion in the human brain, so we're talking about very small scale right now," Farahany said.

Ex vivo brain tissue is another type of model that involves removing slices of human brain tissue from individuals during a surgical procedure. This tissue can be kept alive in the lab and studied.

Chimaeras, meanwhile, involve the transplantation of human cells—derived from stem cells—into the brains of animals, such as rodents, either while the animal fetus is developing or after it's born. This provides researchers with a more natural environment for the human brain cells to mature in.

A real human brain being displayed as part of an exhibition at the @Bristol attraction on March 8, 2011 in Bristol, England. One of the most exciting scientific developments of recent years has been the ability of researchers to develop various surrogates of the human brain in order to learn about neurological diseases. Matt Cardy/Getty Images

As these brain surrogates become ever larger and more sophisticated, the researchers argue that there is a possibility they may begin to experience certain characteristics associated with sentience.

"Such capacities could include being able to feel (to some degree) pleasure, pain or distress; being able to store and retrieve memories; or perhaps even having some perception of agency or awareness of self," the authors wrote.

While we may still be a long way away from this scenario, what factors do scientists, funding bodies and review boards need to discuss?

Detecting consciousness

Firstly, would it even be possible to gauge if a brain surrogate was displaying some form of consciousness?

"I think there's certainly a potential for the development of some sentient capabilities and in order to figure out whether any of them do have any sentient-like capabilities, we need much better metrics to measure what that even means," Farahany said.

"We have a sense in a human being who has consciousness what it looks like when they lose consciousness. But that doesn't mean we're very good at detecting if a different organism, or a different species, or in this case something that starts with human cells, has, or can develop any sentient-like capabilities."

We could say for example, that before an "organoid is allowed to grow quite large that we'd want to see some additional tests," she added.

Human-animal blurring

With the advent of chimaeras that have been implanted with living human brain tissue, the researchers examine the question of how we should define the boundaries of this kind of research.

"We need to ask hard questions about human-animal blurring, for example," Farahany said. "Which things we're comfortable putting into animals and which ones we're not; whether that changes the status of how we treat those animals in research and how we come to regard them.


Brain surrogates could even challenge our understanding of life and death. The idea that a person whose brain has ceased to function can be declared dead—known as brain death—forms part of the legal systems of nations around the world. But any technology that could restore brain functionality could potentially undermine this diagnosis because the cessation of brain function may no longer be irreversible, according to the authors.

Stewardship and ownership

According to Farahany, questions regarding the stewardship of brain surrogates may revolve around " whether we think, ultimately, that any of [them] could develop to a point where they may have some welfare interests that are at stake, and if so, what those interests may be," she said.

For example, a chimaera implanted with human brain tissue may require someone loosely akin to a guardian, who is independent from the researchers, to make decisions on their behalf.

And "who, if anyone, should 'own' ex vivo brain tissue, brain organoids or chimaeras?" the authors ask. "At present, brain tissue samples are owned by the researchers or organizations collecting the tissue or doing the science. If significant developments in the field one day lead us to regard any of these brain surrogates as having greater moral status than we would currently give them, might greater privileges and protections be appropriate?"

Post-research handling

After most experiments on human tissue, the biological material is disposed of once the study is over. And currently, all brain surrogates are disposed of following standard practices. But if researchers one day create mice with advanced cognitive abilities using human brain tissue, for example, should these animals be destroyed in the same way? Nowadays, some research animals, such as chimpanzees, are taken to sanctuaries rather than being destroyed after researchers have finished with them.

Data concerns

There is also a possibility that ex vivo brain tissue could reveal information such as the memories or disease status of the donor. So, the benefits and risks of sharing data obtained from such tissue needs to be seriously considered, the researchers argue. They suggest that there may need to be special requirements for the data sharing and use of such brain tissue.

Farahany concludes that the new article should be a discussion guide, which will enable the research to go forward "responsibly".

"We hope that this spurs a lot more discussion among scientists, among oversight bodies, among the public, to really figure out how do we enable this progress to go forward in a way that we're all comfortable with," the expert said.