The scientific journal Nature.comreports an interesting experiment. Mini-brains grown in a culture plate spontaneously produced human-like brain waves for the first time, and the patterns of their electrical activity appear similar to those seen in premature babies. This advance could help scientists study the early stages of brain development. Research in this area has been slow, in part because it is difficult to obtain fetal tissue samples to analyze and it is nearly impossible to examine a fetus in utero. Many researchers have come to expect a lot from these "organoids" which, when grown as 3D cultures, can develop some of the complex structures seen in the brain. But this technology also raises questions about the ethics of creating miniature organs that could develop consciousness.
In this section of the brain organoid, more mature cortical neurons can be seen on the outer edge of the structure. A team of researchers led by Alysson Muotri, a neuroscientist at the University of California at San Diego, has induced human stem cells to form tissue from the cortex, a brain region that controls cognition and interprets sensory information. The researchers cultured hundreds of brain organoids for ten months, and tested single cells to confirm that they expressed the same set of genes seen in typical human brain development. The group presented the work at the Society for Neuroscience meeting held this month in San Diego. Scientists consistently recorded patterns of electrical activity, the electroencephalogram (EEG), along the surface of the mini-brains. At six months, the organoids began to activate at a higher rate than other previously created brain organoids.
In mature brains, neurons form synchronized networks that are activated with predictable rhythms. But the organoids showed irregular electroencephalographic patterns that resembled the chaotic explosions of synchronized electrical activity that occurred during brain development. When the researchers compared these rhythms with EEGs of premature babies, they found that the models of the organoids imitated those of children born after 25-39 weeks of conception.
The organoids are far from being true human brains, says Muotri. They do not contain all the types of cells found in the cortex, and the circuits do not connect to other brain regions.
But now his group is working to grow the organoids longer and see if they will continue to mature. Researchers also want to investigate whether these structures function as a normal cortex, linking them to organoids that mimic other parts of the brain or body.
"This is really fascinating and very surprising," says Hongjun Song, a neuroscientist at the University of Pennsylvania in Philadelphia. Although the work is preliminary, he adds, the similarities to EEG tracings of pre-term children suggest that organoids could be useful for studying brain development disorders, such as epilepsy or autism.
Song also believes that the study of how EEG traces originate in an organoid may help researchers understand how EEG rhythms emerge in a developing human brain.
But not everyone agrees. Just because the cerebral waves of the organoids resemble those of premature babies does not mean they're doing the same thing, says Sampsa Vanhatalo, the neurophysiologist at the University of Helsinki who developed the children's EEG database used by Muotri for comparison with the measurements obtained from the organoids.
And proving that this is the case will be difficult because researchers know very little about how children's brains are "wired", says Arnold Kriegstein, a neurologist at the University of California at San Francisco. Organoids, he adds, may not have key components that determine EEG patterns in the real brain.
But the project raises ethical questions about whether organoids can develop consciousness, says neuroscientist Christof Koch, president and scientific director of the Allen Institute for Brain Science in Seattle, Washington. "The closer they get to the pre-term infant, the more they have to worry."
But Koch recognizes that it may be difficult to know when an organoid is conscious, because the researchers do not even agree on how one can measure consciousness in adults, or when it appears in newborns.
Muotri says if there was evidence that the organoids have become self-conscious, he would consider discontinuing the project; but right now they are very primitive. "We are in a very gray area at this stage, and I don't think anyone has a clear vision of the potential of this research."
Source: https://www.nature.com/articles/d41586-018-07402-0