Building Your Own Brain
Scientists are using human stem cells to produce ‘brain organoids’
The mass of tissue weighing 1.4 kilograms that lies inside our skull makes up the most complex organ of our body — the brain. This enigmatic organ is made up of neurons, which scientists have been researching for the past 100 years to understand how they develop, connect, function and lead to behaviour.
Brain research is hard. Over 7 billion dollars is invested in neuroscience research per year, but innovations in this area have stalled in late 20th century; the number of novel therapeutics meant for the brain is decreasing. One of the many reasons that studying the brain is difficult is because of the use of animal models.
There is a lot to learn from the posthumous human brain, but it is limited in scope. It cannot tells us what the brain is doing when alive. Animal models, such as rodents or primates, are used as proxies to study the human brain based on the key assumption that certain species of animals have similar brain structures, diseases and behaviours to those seen in humans. Scientists justify this approach because mice and humans share a common brain architecture: they have many of the same types of nerve cells and rely on essentially the same parts of the brain to carry out shared mental processes.
Despite these similarities, there are some fundamental differences between animal brains and those of humans. Thus, the conclusions we draw from clinical trials or research that depend on animal models often do not accurately represent the human brain. This has led researchers to figure out how else to conduct experiments on the human brain.
That’s how we got to building human brains in the lab. Human stem cells can be used to grow miniature brains known as brain organoids. The appropriate signalling factors are combined with pluripotent stem cells causing them to differentiate and self-organize into three-dimensional structures that look like certain regions of the human brain. This process resembles the development of the human foetal brain, which is otherwise impossible to investigate. Additionally, neuroscientists can also gain insights into the development of two types of glial cells: astrocytes and oligodendrocytes.
“Brain organoids offer an in vitro approach to study aspects of human brain development and disease.” They do not simulate model neurological processes; they are those processes.
Evidently, there are constraints to how reliable brain organoids can be. They are too small to fully recapitulate the functioning of the human brain and they also do not always recapitulate distinct cellular subtypes. But, that did not stop Trujillo et al. (2019) from observing coordinated waves of brain activity, similar to those found in premature babies. To many, this is indicative of consciousness.
Understanding the neural correlates of consciousness has been a long endeavour for neuroscience. Certain electrophysiological features have been proposed to be signals of a conscious brain. But, researchers do not agree on one definition. Recent years have seen a rise in the number of theories about the biological and physical basis of consciousness.
This paper has spurred the debate between those who do not want to play god and create consciousness and those who want to continue using organoids has a way to study the human brain. The authors think “that human brain organoids could be the key to understanding uniquely human conditions such as autism and schizophrenia, which are impossible to study in detail in mouse models. To achieve this goal, [they]… might need to deliberately create consciousness.”
The potential for consciousness is an important determination, to many, for determining the moral status of an entity. Should these organoids be deemed conscious, what moral status would we assign them? Would researchers be required to ask for consent? Would they suffer from pain?
In 2021, The National Academies of Science published a report on the ethics and governance of human neural organoids as an attempt to provide guidelines for these emerging questions. One challenge with governing this field is the broad inconsistency in views, knowledge and opinions held by key decision-makers globally. Existing oversight mechanisms in the use of human stem cells, informed consent and the use of biospecimens in research are sufficient to govern the current state of neural organoids. When they become more complex is the issue.
Guidance is definitely welcomed by the scientific community. The question we need to ask is if we are willing to play God to help treat those who really need it.
