There is a "natural" lab in a sprawling estate in New York inhabited by two scientists and a thousand bright yellow canaries and a thousand four hundred zebra finches. They want to find out how birds learn to sing and what happens to their brain cells (neurons particularly) when they do learn to sing. This is the lab that science-writer Michael Specter (New Yorker 2001) visited on his trail to investigate what could be one of the most important scientific mindshifts in neuroscience.
One of the most fundamental principles in neuroscience is that "higher" animals, including humans, are born with essentially all the brain cells (neurons) they will ever have. This explains why diseases that destroy neurons such as Alzheimer’s, strokes and other brain injuries are irreversible. Other brain parts may in some cases be able to compensate for the loss of functions of other damaged parts but no new neurons are produced. However, this long-held belief seems to be changing.
Fernando Nottebohm is one scientist who has blazed this trail to change the belief that we are essentially stuck with the same neurons in our brains till we die. Michael Specter followed him around, digging up Nottebohm’s researches starting with his fascination with birds in his native Argentina. Nottebohm wanted to know how these melodies from birds are born in the cellular level. In other words, he wanted to know if there is anything occurring in the brains of male canaries, known for their entirely new repertoire every season, that enable them to learn a new song. The insight from Nottebohm’s researches was this: as far as canaries are concerned, thousands of new neurons are produced each day. This process is called neurogenesis. This has caused the fundamental shift in thinking in the neurosciences. Neurons are born in the adult brain.
So what if bird brains can learn new songs and get rid of old ones? One important reason these scientists even bother is that it may shed light on the human brain. Birds sing for specific evolutionary purposes – to attract mates, to scare predators, even to signal weather change. These are clearly challenges that birds make calculations and mental maneuvers for, in order to meet and what do you know, in the process, these may even help or even cause their brain regenerate.
Neurogenesis research is still far from being conclusive in its application to human beings. But it is getting closer. Elizabeth Gould, a scientist from Princeton University, is reaching critical mass in terms of followers and critics in this field. Specter also interviewed her and he was told that her most recent work on Old World Monkeys (the ones from Africa and Asia), which are more closely related to humans, revealed that indeed new neurons were found even in the neocortex, considered the most sophisticated region of the brain responsible for language and thought. What is even more insightful is that it seems that there is a strong link between the number of neurons generated and the type of mental challenge the primate faces. Her research suggests that indeed the more primates engage minds to meet the challenges of living, the more equipped they become in terms of mental cells and circuitry.
What if it is really proven, at the cellular level, that engaging the mind in order to live, really gives birth to literal "new-rons"?
There were jokes going around before that some brains are indeed desirable for transplant because they have never been used. That joke may not be so funny if neurogenesis research turns out to be conclusive and applicable to the human brain because then that brain that was never used would be dead from non-use. So to give some thought to everything we do may really be good not only ethically. It may even make good biological sense to do so.