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Lab-grown miniature brains produce brain waves

Researchers from the University of California, San Diego have detected brain waves similar to those found in preterm babies in lab-grown, stem cell-crafted, miniature brains, which are about a million times smaller than developed human brains

These findings are published in Cell Stem Cell.

“The level of neural activity we are seeing is unprecedented in vitro,” said biologist Alysson Muotri, from UC San Diego. “We are one step closer to have a model that can actually generate these early stages of a sophisticated neural network.”

These mini brains, called cerebral organoids, are grown from human pluripotent stem cells placed in a culture that mimics the ideal environment for brain development. The stem cells separate and organize themselves into 3D structures resembling that of a human brain.

However, until now, none of the prior models developed functional neural networks similar to that of a human brain. These networks show up when neurons mature and interconnect, and are essential for most brain activities.

“You can use brain organoids for several things, including understand normal human neurodevelopment, disease modeling, brain evolution, drug screening, and even to inform artificial intelligence,” Muotri said.

Muotri and team redesigned the procedure for growing stem cells in order to allow for neuron development. Their redesign resulted in more mature organoids that began to show bursts of brain waves at about two months old. The older they grew, the more regular the brain waves became.

Cross-section of a brain organoid, Image Credit: Muotri Lab/UCTV

The team then trained a machine learning algorithm with recorded brain waves from several premature babies between six and nine-and-a-half months old in order to compare these brain waves to those of their organoids.

The algorithm successfully predicted how many weeks the organoids had developed in culture, therefore suggesting that the organoids and human brain have a similar growth trajectory. But, it should be noted that these organoids are unlike human brains in that they do not have consciousness.

“The organoid is still a very rudimentary model — we don’t have other brain parts and structures,” Muotri said. “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 behaviors, thoughts, or memory. But I don’t think we have any evidence right now to say we have any of those.”

The hope is that these organoids will be able to help scientists better understand neural network diseases and diagnoses like autism, epilepsy, and schizophrenia. But in order to get there, scientists may face roadblocks when it comes to the discussion of ethics.

“As a scientist, I want to get closer and closer to the human brain,” Muotri said. “I want to do that because I see the good in it. I can help people with neurological conditions by giving them better treatments and better quality of life. But it’s up to us to decide where the limit is. It might be that the technology is not ready yet, or we don’t know how to control the technology. This is the same kind of discussion around CRISPR in babies, and that’s why we have ethics committees to represent all parts of the society.”

By Olivia Harvey, Staff Writer

Main Image Credit: Muotri Lab/UCTV

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