A neural network derived from a cerebral organoid Takahashi et. al / Stem Cell Reports

Scientists growing miniature brains in a lab have created neural networks that act like those in the human brain. They hope the discovery will enable cheaper and easier research into brain diseases and drug development.

In recent years researchers have been working on creating small, three-dimensional human brains, or cerebral organoids. The hope is that they will eventually replace animal models, imaging techniques and autopsies as tools for understanding the brain.

These simplified organoids have some of the architecture of the brain’s cerebral cortex – which is responsible for many of the features that make us human, such as thinking, perceiving, memory and language.


They have already been used to model diseases such as microcephaly, Zika infection and glioblastoma. But little is known about how the neurons within them communicate with each other, says Hideya Sakaguchi of the Salk Institute for Biological Sciences in California.

Self-organising

To investigate, Sakaguchi and his colleagues at Kyoto University took a ball of stem cells and grew an organoid with layered tissues that had a similar structure to the cerebral cortex. After about three months, the team took individual cells from the tissue and grew them separately in another dish. These cells began to organise themselves into clusters and form networks with other nearby clusters.

The team then studied calcium ion binding, a method of detecting neural activity, to see how and when the neurons within the clusters fired.

Find out more about miniture organs: Vivian Li at New Scientist Live in London this October

Sakaguchi says that at first, neurons fire individually, but as they form networks and connections with other neurons they begin to operate in a synchronised fashion. This is an important discovery, because synchronised neural activity is believed to be the basis of various brain functions, including memory.

Another important finding was that the neurons would occasionally spontaneously fire. This is thought to be one of the ways that neurons in the brain grow and create new connections.

Ethical questions

Sakaguchi thinks the neural networks will help with drug discovery, better modelling of neuropsychiatric disorders and perhaps eventually open the door to regenerating chunks of the brain after disease or physical trauma.

But given that the cerebral cortex has an important role in human consciousness, ethicists will be watching the development of cerebral cortex-like organoids closely. Nevertheless, Sakaguchi says the current technology is a long way off a ‘thinking’ brain.

“To create higher brain function such as consciousness or thinking, I think organoids need subjective experiences, and it needs sensory input and motor output system at the same time,” he says.

Sakaguchi says that the current lab-grown organoids lack those experiences – but he is worried that future developments might bring them closer to consciousness.

Journal reference: Stem Cell Reports, DOI: 10.1016/j.stemcr.2019.05.029