MARY LOUISE KELLY, HOST:
Next up - scientists say clusters of human brain cells grown in a lab can produce brain waves like those of a premature baby. But as NPR's Jon Hamilton reports, this sort of research is raising some ethical questions.
JON HAMILTON, BYLINE: They start out as just a few stem cells in a dish. But with the right sort of assistance from researchers, they can grow into spheres the size of a pea. And these minibrains - scientists prefer to call them brain organoids - begin to look and act like human brain tissue. So Alysson Muotri of the University of California, San Diego, decided to have his lab monitor the electrical signals coming from these organoids. He says, early on, there were just a few spikes of electrical activity, and then...
ALYSSON MUOTRI: We realized that the number of spikes from these electrodes were too many. We'd never seen that before.
HAMILTON: As the organoids matured, the spikes became even more common, and they started to occur at different frequencies.
MUOTRI: And what we could tell is that not only the neurons are connecting to each other, but they are forming microcircuitries. That's when we started seeing these brain waves.
HAMILTON: Muotri says it became clear that brain cells were communicating with one another and forming networks.
MUOTRI: We thought, wow, I mean, it's nice that we have this system, but how close is that to the human brain?
HAMILTON: To find out, the team trained a computer to recognize the brain waves produced by babies born prematurely. Muotri says then they had the computer look at the brain waves from organoids as they grew and matured in the lab.
MUOTRI: After 25 weeks, the machine gets really confused. It can no longer distinguish the brain waves coming from the human brain and the brain waves coming from the organoids.
HAMILTON: The research appears in the journal Cell Stem Cell. And Muotri says it suggests that organoids offer a way to study a wide range of brain problems that start before birth.
MUOTRI: For example, psychiatric conditions such as schizophrenia, bipolar, depression, or neurological conditions such as autism, that have origins in the very early stages of brain development.
HAMILTON: Ethicists say brain organoids do have huge potential, but that this sort of research needs some guidelines. Nita Farahany of Duke University is a member of the Neuroethics Working Group assembled by the National Institutes of Health.
NITA FARAHANY: If we're starting to see spontaneous brain activity that grows and develops as the organoid grows and develops, then we need to have some concerns about how ought we regard these things. Do they have some moral status?
HAMILTON: Farahany says there is still a big difference between an actual human brain and a brain organoid. For example, the human brain has a million times more cells, and it's connected to the world through our senses. But she says organoids keep getting more complex and capable, and they can now live for years in a lab.
FARAHANY: The big questions in organoids are, will they ever develop any sentience-like capabilities, you know, any perceptions of pain or perception whatsoever?
HAMILTON: On the other hand, she says organoid research is really important because scientists have been unable to replicate many human brain problems in animal models.
FARAHANY: If we don't have good models to study the human brain, the potential for being able to address so much human suffering, disease - things that are very difficult to model in animals - we'll never reach. And so we have to figure out an ethical way to enable this research to progress.
HAMILTON: Farahany says the NIH and other organizations recognize the problem and are beginning to offer scientists some guidance.
FARAHANY: There's work that's being done, but that work needs to speed up because the science is going very quickly.
HAMILTON: For example, scientists at Harvard have already developed brain organoids that respond to light.
Jon Hamilton, NPR News.
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