Revelations that brain waves have been detected in lab-grown human brains have prompted one Kiwi professor to ask, "Should science have a limit?"
Scientists in the United States have created miniature brains from stem cells which developed their own neural networks. The lab-grown human brains are roughly the size of a pea, and are the first observed to produce brain waves similar to preterm babies. The scientists' findings were previously reported in the Nature journal last year.
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Scientists have previously grown organoids with cellular structures similar to human brains, but none have developed human-like, functional, neural networks.
"The level of neural activity we are seeing is unprecedented in vitro," said University of California biologist Alysson Muotri on Friday, when a new paper on the brains was published in journal Cell Stem Cell.
"We are one step closer to have a model that can actually generate these early stages of a sophisticated neural network."
But Professor Jing-Bao Nie from the Centre for Bioethics at the University of Otago said the development suggests "it is time again to ask the fundamental questions".
"What is science ultimately for? How can unintended harmful and evil consequences be prevented in the pursuit of 'good'? Should science have a limit?"
Dr Nie said they were questions not just for scientists alone but to be "moderated by the inputs of each and every citizen".
"Are we sure what fate our collective hubris for science takes us to?"
Dr Muotri noted ethics committees were in place during the research.
"It might be that the technology is not ready yet, or we don't know how to control the technology."
Dr Muotri said growing the brains would help scientists understand human neurodevelopment, disease modelling, brain evolution, drug screening and even help inform artificial intelligence, and help people with neurological conditions by understanding them and giving them better treatments.
The brains were grown over 10 months, the scientists using 'multi-electrode arrays' to monitor their neural activity. At two months, bursts of brain waves were detected similar to what is found with very immature human brains.
But as the organoids grew, signals of the brain waves became more regular, suggesting the development of a neural network.
Despite the advancement, Dr Muotri says it is not likely the organoids have mental activities, like consciousness.
"The organoid is still a very rudimentary model - we don't have other brain parts and structures. So these brain waves might not have anything to do with activities in real brains.
"It might be that in the future, we will get something that is really close to the signals in the human brains that control behaviours, thoughts, or memory... But I don't think we have any evidence right now to say we have any of those."
A more positive response to the research came from Prof Bronwen Connor from the Centre for Brain Research at the University of Auckland, who said it presented an "exciting and significant advancement" and would help in investigating neurodevelopment disorders like autism.
"This capability will greatly enhance the ability to identify and develop new treatment strategies for currently untreatable neurodevelopmental conditions."