Tiny lab-grown 'brains' can gain consciousness and feel pain—and we're not ready for that.

Some scientists claim that miniature brain models grown in labs could soon achieve consciousness. However, our current regulations don't allow for this. (Image courtesy of Francesco Carta fotografo via Getty Images)

Scientists are getting closer to growing human brains in the lab, sparking ethical debates about the welfare of these lab-grown tissues.

Controversy surrounds “brain organoids,” sometimes mistaken for the “brains in boxes” of science fiction. However, these small structures of brain tissue, grown from stem cells, are too simple to function like a real human brain. Consequently, scientists have suggested that brain organoids lack consciousness, leading to lax research regulations.

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Most neuroscientists define consciousness as self-awareness or the ability to feel or experience something, University of California, San Diego neuroscientist Alisson Muotri told Live Science in an email. However, he notes, there is no universally accepted definition.

Some definitions of consciousness focus on the brain's ability to process information and respond to the environment through sensory organs such as vision and hearing. Brain organoids are cultured outside the body and cannot receive such signals, Lavazza noted. However, in the future, more advanced organoids could theoretically experience pain. In humans, the membranes covering the brain, called the meninges, contain neurons capable of sending pain signals to the organ. There is concern that the same could be realized in more complex organoids.

On the other hand, Boyd argued that “if an organoid possesses the internal neural architecture necessary for pain representation, then no external signal is required.” Thus, the presence of a pain signal from a neuron is not necessary for pain to occur; this is precisely how phantom pain occurs in people who have lost limbs.

Wood, however, noted that it's unclear whether the organoid can experience anything like phantom pain, as this may depend on the presence of a memory of the lost limb. In short, it's complicated.

How to measure consciousness?

The article noted that even in humans, scientists lack effective methods for objectively measuring consciousness. Lavazza stated that the only way to accurately determine the presence of consciousness is to ask a person what they are feeling. This doesn't mean that people who are unable to communicate lack consciousness, but it's more difficult to accurately measure.

According to Lomax, for patients in comas or with locked-in syndrome—a neurological disorder that paralyzes the body and severely impedes communication—doctors rely on indirect signals, such as electrical activity in the brain. From this activity, they can only infer consciousness, but not make precise measurements.

An array of microscopic images of chimeroids, a type of brain organoid grown from stem cells from several people.

Another measure includes “perturbative complexity,” which assesses the complexity of brain signals generated in response to a stimulus, such as a magnetic field applied to the scalp. Doctors believe that the more complex the neural activity patterns, the higher the likelihood that the patient is conscious, Lomax said.

However, some indirect signals of consciousness, including perturbative complexity, can be observed even in neurons grown in vitro, he emphasized. This suggests that they are not good indicators of this phenomenon.

Complexity breeds consciousness

Skeptics who doubt that brain organoids can become conscious argue that they lack the necessary anatomical complexity, including a wide range of cell types and blood vessels to deliver oxygen and the resources needed for complex signaling.

But in the next five to ten years, technological advances could allow scientists to create complex organoids with consciousness, Wood said. A study published in August reported a method for introducing blood vessels into brain organoids, while another, published in September, found ways to introduce an additional type of cell called microglia, which cannot be obtained from neural stem cells. Previously, scientists have grown brain organoids with rudimentary “eyes,” while another group of scientists grew organoids with a blood-brain barrier, which helps protect the organ from toxins and pathogens.

Although modern organoids resemble only a single brain region, neuroscientists can group them into “assembloids” representing multiple regions. Lavazza stated that such assembloids are likely capable of feeling pain if they carry the neural network necessary for pain perception—even if they lack pain neurons.

Should the rules change?

Regulations regarding brain organoid research are somewhat lenient, as the International Society for Stem Cell Research (ISSCR) maintains that these structures are incapable of pain perception. Its guidelines state: “There is currently no biological evidence to suggest any issues, such as consciousness or pain perception, in organoids corresponding to CNS [central nervous system] tissues that would require consideration under a specialized oversight procedure.”

However, experts Live Science spoke with agreed that the rules should be revised in light of recent breakthroughs in organoid development.

“This was a very conservative vision of the ISSCR and it needs to be revisited with a multidisciplinary team, not just stem cell biologists,” said Muotri, founder of Tismoo, a company that develops brain organoids.

Ethical concerns are partly related to the organoids' potential ability to feel pain and form their own thoughts. “The well-being of a conscious organoid once created must be considered, as it becomes a morally significant entity with its own interests,” Wood explained.