Stem cell research has been a hotly debated issue for years already, but groundbreaking work utilizing stem-cell-grown human brain tissue is about to challenge even the most lax definitions of medical ethics. Two groups of researchers are poised to present their work regarding the implantation of human “mini brains” into rodents, and the potentially horrifying results that followed.

The two papers, summaries of which have reportedly been submitted prior to their presentations at this year’s meeting of the Society for Neuroscience, reveal that not only did the human brain tissue survive for extended periods of time, but that it actually began to integrate with the hosts in unexpected and incredible ways.

The tiny brain blobs, which scientists call “organoids,” were able to be successfully implanted from their lab-grown conditions into living mice. Once implanted, the brain tissue melded with the rodent’s circulatory system, allowing it to remain alive for an extended period of time. Then — and this is the part that should really send a chill up your spine — the human brain tissue actually managed to connect itself to its host’s nervous system, sending the tiny “wires” that carry nerve signals to “multiple regions” of the mouse’s own brain.

The researchers stopped short of saying whether or not this clear connection between the human brain tissue and the rodent brain caused the test subjects to behave differently, or if it appeared as though the mice had any shifts in intelligence or reasoning, but that is likely to be expanded upon once the research is formally presented.

“It brings up some pretty interesting questions about what allows us, ethically, to do research on mice in the first place — namely, that they’re not human,” Josephine Johnston, a bioethicist with The Hastings Center, says. “If we give them human cerebral organoids, what does that do to their intelligence, their level of consciousness, even their species identity?”

These are all questions researchers will have to answer as they continue to consider the implications of using artificial human brains in experiments and trials such as these. At the moment, it seems as though ethics is taking a back seat to scientific glory.

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