A team of researchers led by Duygu Kuzum, an assistant professor at the University of California San Diego's Department of Electrical and Computer Engineering, conducted an experiment by implanting a human brain organoid in mice.
For the first time, such an experiment gave positive results as the implanted human brain organoids proved able to establish connections with the animal's brain cortex.
"No other study has been able to record optically and electrically at the same time," Madison Wilson, the paper’s co-author, said. "Our experiments reveal that visual stimuli evoke electrophysiological responses in the organoids, matching the responses from the surrounding cortex."
To observe the experiment's results, scientists placed a transparent graphene electrode on top of the organoid cells. When combined with two-photon imaging, this allowed the brain tissue to be studied to a thickness of up to one millimeter. Thus, the team was able to see how the blood vessels of the mouse's brain penetrated the organoid and begin to nurture it with everything the organoid cells need to live. Electrode sensors captured neuronal activity in the organoid and in the native visual cortex of the mouse's brain.
The experiment showed that flashes of light in front of the mouse's eyes were accompanied by the activity of organoid tissues. To put it simply, the tissues of the "human" mini-brain were implanted into the structure of the mouse brain and began to react to external stimuli which enabled the scientists to say with certainty that for the first time an artificial brain has responded like a real one.
"This experimental set-up opens up unprecedented opportunities for investigations of human neural network-level dysfunctions underlying developmental brain diseases," Kuzum said.