Researchers attending the world's largest annual meeting of neuroscientists in Chicago this week will discuss the ethics of growing lumps of human brain in labs, and what they do with it.

"If there's even a possibility of the organoid being sentient, we could be crossing that line," said Dr. Elan Ohayon, the director of the Green Neuroscience Laboratory in San Diego, California.  "We don't want people doing research where there is potential for something to suffer."

There's good reason to develop these lumps of human brain tissue called "organoids":  Researchers use them to investigate schizophrenia and autism, of anything else that might go wrong with the natual development of a human brain such as the microcephaly that occurs in babies who are infected with the Zika Virus while in the womb.  Research applications could range from searching for ways to prevent Alzheimer's and Parkinson's to seeking sures for age-related macular degeneration.

But in some research, organoids have been transplanted into lab animals.  Dr. Fred Gage of the Salk Institute in San Diego led a team that transplanted human brain organoids into mouse brains and found that they connected up to the animal's blood supply and sprouted fresh connections.  

Harvard researchers found that organoids develop a rich diversity of tissues, from cerebral cortex neurons to retinal cells.  Organoids grown for eight months developed their own neuronal networks that sparked with activity and responded when light was shone on them.

And some created brain waves similar to those seen in premature babies, leading many to wonder if science hasn't crossed an ethical line.

"We're already seeing activity in organoids that is reminiscent of biological activity in developing animals," said Dr. Ohayon, who will bring his presentation to the Society for Neuroscience meeting in Chicago.  Ohayon and his colleagues Ann Lam and Paul Tsang will argue that checks must be in place to ensure that brain organoids do not experience suffering.