What is Neurogenesis?: Regrowing Your Brain
“…I have experience recovering from a stroke. At the age of seven I underwent a stroke that almost took my life and paralyzed me on the left side of my body as well as from the waist down, leaving me in a wheelchair. But through years of therapy, working alongside neurologists, and my brain’s neurogenesis ability, my body and brain have recovered and I am in full health”
“Can you grow new brain cells?”
You may have heard at some point in your life that you cannot grow new brain cells. You may have been taught that from the moment you are born to when you die you can only lose brain cells. It is believed that this is due to hits to the head, consuming alcohol and narcotics, and from lack of cognitive stimulation. Well do not despair because your brain is not in danger, you can in fact “grow” new brain cells in a process called neurogenesis.
Before I explain this process, I would like to get you up to speed to clear any confusion. As you may know or have learned, what people typically refer to as a “brain cell” is the more colloquial term for the neuron. These are the cells that make up the nervous system including the brain and through the communication of neurons, we achieve thought, actions, and everything that makes a brain a functioning organ.
It is typically believed that we develop billions of neurons during fetal development and that is it! After our brains develop, it is believed that the only changes that occur in our brains are the pruning and changing of synapses (the junction between neurons used for communication). So through this belief, it is believed that concussions, alcohol consumption, and stroke cause us to lose neurons and they can never be replaced. Unlike the rest of our body, our brains cannot heal. If you receive a cut on your hand, your blood will clot and form a scab until new skin cells repair the damage. As you grow, your bone cells develop and your bones elongate, being replaced by new cells. Our organs themselves have the ability to grow, change, and be replaced, however, it is believed that the brain is just a stagnant organ that can only lose its cells and never undergo repairs and growth.
Luckily for us, this is a FALSE belief!
The ability the brain has to develop new neurons is coined “neurogenesis” (“neuro” = relating to the nervous system; “genesis” = the formation of something new). The root of the word properly defines the term, but why is it that we have been taught otherwise about our brain’s ability to develop new cells?
A quick neuroscience history, Santiago Ramón y Cajal, the forefather of neurobiology incorrectly proposed the “harsh decree” of neuroscience. Ramon y Cajal believed that no new neurons were generated in the adult mammalian central nervous system. You cannot blame him though, because before Ramon y Cajal, people thought the brain was just a reticulum. It was Ramon y Cajal who discovered that the brain is comprised of small units working together to form the neural net that is the brain. Ramon y Cajal was the first to work with advanced microscopy techniques during his time, in the year 1913. Ramon y Cajal discovered a lot for modern neuroscience so we will let this one error slide.
However, his “decree” was taken as a fact of neuroscience for years extending into the 1960’s when Joseph Altman and Gopal Das at MIT were finding evidence in rats, cats, and guinea pigs that these animals were able to develop new neurons. In their studies, the researchers found that these animals underwent neurogenesis in the hippocampus (a region of the brain responsible for developing new memories) and in the olfactory bulbs (a region of the brain involved in the sense of smell). Although Altman and Das had their research published in highly accredited academic journals, the dogma of Ramon y Cajal’s “harsh decree” was still taken as truth by neuroscientists at the time and their findings were silenced.
Fortunately, since the 60’s the neuroscience community has reduced their ignorance and it is now the topic of many researchers to discover new areas undergoing neurogenesis. It has been found that New York City taxi drivers have large hippocampi due to their spatial memories. Taxi drivers have an incredible ability to retain the vast network of streets and buildings which results in larger hippocampi due to the neurogenesis in this part of the brain.
It is reassuring to learn that we are not constantly losing brain cells and losing cognitive ability. This is the whole premise behind CogniFit. Through brain training games and exercises we can learn how to improve your IQ, become sharper and faster in decision making, and overall improve our cognitive abilities thanks to neurogenesis and neuroplasticity. It has been found that we develop about 700-1000 new neurons in the hippocampus a day as adults (Spalding 2013). Although this number seems minuscule on the grand scheme of the billions of neurons that comprise the brain, over the years these 700 neurons add up to over 12 million neurons by the age of 50. These 12 million neurons are enough to completely replace the hippocampus alone.
Neurogenesis is such a new field of neuroscience that even experts in the field are still very uninformed on the subject. However, Dr. Sandrine Thuret is making efforts to introduce this new study of neurogenesis into the community and has sufficiently summed up the topic in her TEDTalk.
Do neurons die?
It is reassuring for those who experience head trauma, alcohol consumption, or stroke to hear that their brain cells are not lost forever. Although these can be difficult events to overcome (trust me, that hangover will eventually go away), head trauma and stroke are injuries that one can heal from.
Not only do I have experience with a hangover, I have experience recovering from a stroke. At the age of seven I underwent a stroke that almost took my life and paralyzed me on the left side of my body as well as from the waist down, leaving me in a wheelchair. But through years of therapy, working alongside neurologists, and my brain’s neurogenesis ability, my body and brain have recovered and I am in full health! I am not saying that I physically felt the neurons developing in my brain, but what I am saying is that there is hope.
In terms of head trauma such as concussion and alcohol consumption, your neurons are not literally dying. These types of brain damages are temporary, and they do not affect the cells directly, but more so effect the communication between cells, those synapses I was talking about earlier. Although you may not have to go through vigorous physical therapy to overcome a bump to the head or a night out with friends, there are other methods you can use to boost your brain’s neurogenesis. There are superfoods for your brain that you can consume that can truly boost your brain’s development and neurogenesis such as the intake of flavonoids, blueberries, or chocolate. Or you can try to pair these nutrition tips with specific exercise techniques such as intermittent fasting and calorie restriction to really increase your brain’s development. Using these techniques you can guarantee yourself a healthy brain that will continue growing through neurogenesis!
Test your knowledge-See how well you know your brain!
Altman, J., & Das, G. D. (1965). Autoradiographic and histological evidence of postnatal hippocampal neurogenesis in rats. Journal of Comparative Neurology, 124(3), 319-335.
Ramón y Cajal, S. R. (1913). Estudios sobre la degeneracion del Sistema nervioso. Moya.
Spalding, K. L., Bergmann, O., Alkass, K., Bernard, S., Salehpour, M., Huttner, H. B., . . . Frisén, J. (2013). Dynamics of hippocampal neurogenesis in adult humans. Cell, 153, 1219-1227.
Eric is a neuroscience researcher with a background in psychology and biology. He is particularly interested in cognitive and behavioral neuroscience and he uses animal models to study stress and drug relapse. Eric is currently in the process of publishing his own research and enjoys staying up to date with the forefront of neuroscience.