Although the organoids are an important step forward, the researchers are nowhere near being able to model circuits found in the functional central nervous system. Moreover, Knoblich said, sensory input is required for such functional circuits to form. A classical experiment showed that the optic cortex will not organize properly if it does not have input from an eye, he said.
Knoblich is also pessimistic about the idea of growing brain structures from stem cells with the intention of replacing faulty ones in human patients. The brain is so complex, and its regions so intimately integrated, that it would be difficult to repair any specific part through substitution.
A more promising possibility, he said, would be to put the stem cells directly into the patient and let them organize themselves. But the future of this line of research is still unknown.
Brustle, who was not involved in this research, called the study "remarkable" and noted that it "clearly puts neural aggregation cultures on the map of research tools for both developmental biology and biomedicine."
That's a lot from a little tissue.