For years, scientists have been growing miniature, pea-sized clusters of neurons and other cells—called brain organoids—in the lab. These remarkable structures, derived from human skin cells, mimic the early stages of brain development, offering a powerful new tool for understanding how our brains form and what goes wrong in neurological disorders.
Growing Brains in a Dish: A Novel Research Approach
In a Harvard lab, Dr. Paola Arlotta and her team routinely inspect racks of “scientific muffin pans.” Within each cavity sits a pool of pink liquid, housing dozens of translucent nuggets – brain organoids composed of up to two million cells. These aren’t actual brains, Dr. Arlotta emphasizes, but rather “reductionist replicas” that allow scientists to study aspects of brain development without the ethical complexities of working with human brains.
A Decade of Development: From Skin Cells to Maturing Neurons
The journey begins with skin cells donated by volunteers, which are transformed into progenitor cells resembling those found in the fetal human brain. These cells then multiply, developing into neurons and other brain cell types, establishing connections and pulsing with electrical activity. Dr. Arlotta’s oldest organoids are now seven years old and offer a unique record of brain development. Remarkably, the neurons within these organoids demonstrate a progression mirroring that of a developing human brain, resembling those of a kindergartner in a five-year-old organoid.
Expanding Applications in Neuroscience
The field of brain organoid research is rapidly expanding, enabling scientists to:
- Trace cellular development: Observe how cells develop and migrate during fetal development.
- Study external influences: Investigate how factors like sugar and other compounds affect brain development.
- Model neurological conditions: Generate brain organoids from cells of individuals with conditions like autism to study how genetic mutations affect neurons.
“Every month, you don’t know what is coming,” says neuroscientist Benoit Laurent, highlighting the dynamism of the field.
Ethical Considerations and the Rise of “Organoid Intelligence”
As brain organoids become more sophisticated, the need for ethical oversight grows. Dr. Arlotta and 16 other scientists recently called for global oversight, emphasizing the importance of focusing on what organoids actually are, rather than speculative possibilities. Start-up companies promoting “organoid intelligence” and building A.I. computers using organoids face scrutiny, with some critics calling their claims premature.
The P.R. has gone way ahead of what’s been done,” says neuroscientist Sergiu Pașca, cautioning against attributing intelligence to simple cell cultures.
Assembloids and the Study of Pain Signals
Scientists are now combining multiple organoids into networks called “assembloids” to study more complex processes. One such creation by Dr. Pașca and his team replicated the pain pathway, observing how neurons responded to stimuli, even exhibiting synchronized firing—a key aspect of pain processing. By introducing a mutation known to increase pain sensitivity, they showed that synchrony was amplified, offering a model for further investigation.
Exploring Artificial Intelligence with Brain Organoids
Biomedical engineer Feng Guo is pushing the boundaries of organoid research by exploring their potential for processing information. His Brainoware system allows electrical signals to be delivered to and from organoids, enabling researchers to observe their electrical activity. In one experiment, Brainoware successfully decoded vowel sounds after a short training period, demonstrating a rudimentary form of artificial intelligence.
Addressing Concerns About Consciousness and Suffering
While full-blown consciousness remains a distant possibility, bioethicist Insoo Hyun raises concerns about the potential for organoids to exhibit memory and a continuity of experience, especially in larger, more intricate networks. Despite the possibility of rudimentary forms of consciousness, Dr. Hyun stresses the more pressing concern: the potential for organoids to suffer.
What I’d be more concerned about is memory, and a continuity of experience,” Dr. Hyun said.
Dr. Arlotta’s ongoing experiments involving light stimulation on her oldest organoids suggest they could continue to evolve, potentially adding complexity and longevity to these unique biological models. The future of brain organoid research promises continued advancements in our understanding of the human brain, its development, and the complexities of neurological disease.
