Molecular biology — biology at the level of its constituent DNA, RNA, proteins, lipids and sugars — beginning with Watson and Crick’s catalytic discovery of how DNA codes genetic information in the arrangement of its four bases, has been one of science’s greatest achievements in the last almost 75 years.
One astounding part of this story is that just as cells differentiate from a single fertilized eggs into hundreds of different mature cell types each with highly specific jobs to do, so can mature highly differentiated cells such as adult human fibroblasts, be coaxed to return to a much earlier stage in development, from which they can be redirected to develop into cells capable, for example with the right molecular prompts, of developing into version of layered foetal neocortex.
These miniature versions of fetal neocortex tissue form organoids, clumps a few millimetres at their widest, which faithfully reproduce the genetic script governing early cell differentiation, migration and the formation of the neocortex, including some budding connections between neurons.
But that’s as far as they go, because without a blood supply, and dependent on diffusion in tissue culture for oxygen, they’re doomed to go only so far, but no further.
Neat as these organoids may be, why would we be interested in creating something that lasts only for a matter of days? Because many genetically transmitted diseases of the nervous system influence the earliest stages of cell differentiation, migration and connections.
Beyond those diseases, the study of brain organoids provides a detailed map of differentiation at the genetic and molecular level, otherwise impossible for humans. That in itself is valuable but has its curious side interests. For example, it turns out that a difference in one amino acid in one protein, created by one gene, can make a huge difference in how the organoid neocortex develops.
A neanderthal version of this one gene leads to a simpler version of the neocortex — fewer neurons and fewer connections — compared to a human version of the same gene. Who would have guessed that a single gene, indeed a difference in one amino acid, in one protein, could make such a big difference in the development of the brain? Not me until I read the article.
Recently, similar tactics have been used to create organoids of a complete system. One example, one study created a motor system from cells in the motor cortex and their connections with motor nerve cells in the brainstem and spinal cord. Another system created a sensory version including sensory cells in the spinal cord, thalamus and sensory cortex.
Readers can see where this might be going. If sub-systems in the nervous system can be created and connected with each other in meaningful ways, could a brain be created from its constituent systems?
Certainly not any time soon, for without a proper vascular system to nourish the nervous system, development would be as stunted as it is in current versions of nervous system organoids. However, incorporating a vascular system with an artificial pump to begin with, might do the trick or perhaps a more natural heart could be developed later.
There’s another problem. For any nervous system to work properly, different regions have to talk to one another and just as important, to the body’s systems and the outside world through some version of vision, hearing and other sensory inputs. Who would want to do all that, and is it even possible, or desirable, or even unethical to try?
Some readers will recall the Star Trek series in the later twentieth century. It was science fiction at its best sometimes and never better than one show in which Data, a very clever robot serving on the Star Ship Enterprise was challenged by a scientist who claimed that as Data was a robot, he wasn’t sentient and if not sentient, could be taken apart to understand how he was created.
A court was summoned to hear arguments pro and con, and eventually, the final judgement was made that Data was indeed sentient and therefore entitled to all the rights and privileges of humans.
The same issue is often posed these days with artificial intelligence. Could future generations of AI be considered sentient and as with the case of Data and the Star Trek court, might AI be entitled to all the privileges and respect of humans?
Certainly, it won’t be long, if we’re not there already, when AI will possess general intelligence equivalent to and probably well beyond humans. Some versions of AI already show evidence of social and emotional intelligence beyond some national leaders these days.
And then there’s the case of hybrids of AI and humans. Such combinations already exist for those who have lost their speech or, in some instances, their ability to walk, and at least one paper claimed recently that a similar device could read human thoughts.
Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.
