Clusters of human brain cells can integrate into rat brains, and that’s raising concerns about giving animals some form of human consciousness.
Researchers can grow stem cells into tiny clumps of cells, called organoids, that display similar activity and structure to human brains. To find out more about how exactly that works, read our primer from when we made the technique one of our Ten Breakthrough Technologies of 2015.
Now, though, reports Stat, several labs have inserted those organoids into rat brains and connected them to blood vessels; some of the organoids have even grown physical links with the rat brains. From Stat’s report:
Some of the axons grew as much as 1.5 millimeters, connecting to the corpus callosum, a bundle of neurons connecting the left and right cerebral hemispheres. When the scientists shined light on a rat’s eye, or stimulated brain regions involved in vision, neurons in the implanted organoid fired. That suggested the human brain tissue had become functionally integrated with the rat’s.
The aim of this kind of research is noble: to work out how lab-grown clusters of brain cells could be used to understand or even treat brain diseases or injuries. But while a handful of cells in a rat brain may not be a problem now, and the idea of imbuing animals with human characteristics or consciousness seems distant, the integration reported by the labs in Stat’s report is giving some ethicists cause for concern.
That’s especially the case as the number of organoids placed inside a rat’s head increases. “People are talking about connecting three or four,” says Stanford bioethicist Hank Greely to Stat. “But what if you could connect 1,000? That would be getting close to the number of cells in a mouse brain … At some future point it could be that what you’ve built is entitled to some kind of respect.”
The inside story of how ChatGPT was built from the people who made it
Exclusive conversations that take us behind the scenes of a cultural phenomenon.
How Rust went from a side project to the world’s most-loved programming language
For decades, coders wrote critical systems in C and C++. Now they turn to Rust.
Design thinking was supposed to fix the world. Where did it go wrong?
An approach that promised to democratize design may have done the opposite.
Sam Altman invested $180 million into a company trying to delay death
Can anti-aging breakthroughs add 10 healthy years to the human life span? The CEO of OpenAI is paying to find out.
Get the latest updates from
MIT Technology Review
Discover special offers, top stories, upcoming events, and more.