Historically, scientists have had a hard time studying early brain development because of how difficult it is to obtain fetal-tissue samples or examine the fetus in utero. However, this may soon change as scientists have grown ‘mini brains’ in dishes that have spontaneously produced human-like brainwaves with electrical patterns quite similar to those found in premature babies.
This was made possible thanks to the efforts of researchers led by neuroscientist Alysson Muotri of the University of California, who coaxed human stem cells to form tissue from the cortex. This is a region of the brain that controls cognition and interprets sensory information. The team grew hundreds of brain organoids (tiny, self-organized three-dimensional tissue cultures that are derived from stem cells) over a period of 10 months, testing individual cells to confirm that they expressed the same collection of genes seen in typical developing human brains.
The group presented their work at the Society for Neuroscience meeting in San Diego this month.
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Muotri and her team continuously recorded electroencephalogram (EEG) activity across the surface of the mini-brains. It was found that by six months, they were firing at a higher rate than brain organoids created previously and resembled firing patterns of babies born 25-39 weeks post-conception.
However, Muotri clarifies that the organoids are not close to being real human brains as they don’t contain all the cell types found in the cortex and don’t connect to other brain regions.
Regardless, the researchers continue to work to grow the organoids for longer to determine whether they will continue to mature. They also plan to explore whether the organoids can function like a normal cortex by hooking them up to organoids that simulate other parts of the human body.
Christof Koch, president and chief scientific officer of the Allen Institute for Brain Science in Seattle, Washington has said the project raises ethical questions about whether organoids could develop consciousness. “The closer they get to the preterm infant, the more we should worry,” he said.