‘Cerebral organoids’ have much to teach us

For all our intelligence, we are still far from sure how the brain works

The human brain is the most mysterious, complex structure in the known universe. In affording us the capacity to reflect upon our own existence, it may be responsible for such horrors as, say, Napoleon’s march on Moscow; but it also allowed Leo Tolstoy to turn the slaughter into the soaring artistic achievement that is War and Peace.

For all our intelligence, however, and despite many decades of scientific endeavour, we are still far from sure how the brain works. And although we have come a long way in building technological versions, a computer is no real alternative – Deep Blue’s victory over Gary Kasparov says more about the nature of chess than about the nature of the human mind. Meanwhile, brain researchers have had only mathematical models, dead bodies and living people upon which to base their studies.

All that may be about to change. Now, for the first time, there is a real possibility of creating an organic brain.

The process itself is wondrous enough. Stem cells made from tweaked skin cells are used to produce neuroectoderm – the embryo cells from which brains develop. With the help of a gel “scaffold” and a spinning bioreactor, these then grow into a “cerebral organoid”, complete with recognisable structures such as cerebral cortices.

The research implications are more staggering still. At this stage, without a blood supply, a lab-brain grows to only 4mm, equivalent to that of nine-week-old foetuses. Even so, it could revolutionise both our understanding of brain development and the design of drug treatments.

But such steps forward bring ethical challenges. Scientists are already working on ways to allow the cerebral organoids to grow larger. At some point, though, a line will have to be drawn. Because at some point in a brain’s development it achieves its final form: human consciousness.