I have always found the brain fascinating. The three-pound wrinkly mass in our heads that controls everything we will ever do, feel, think, learn and store in our memory. It controls our every movement, blink, heartbeat…
There are great number of amazing facts about the brain. It is often quoted that there are about the same number of neurones (brain cells) in the brain as stars in our galaxy. At peak growth rate during development, an astonishing 4000 new neurons are created every second. The brain has hundreds of times more memory and processing power than the worlds most powerful super computers of today. Not only that, a brain is capable of emotion, common sense, imagination and creativity. I could go on.
The traditional view and one that has been taught for generations is that you are born with all the neurones you will ever have and if a brain cell dies, it is never replaced . However in the last decade or so, much has been learnt about the adult brain and it has finally been accepted that this is not the case.
The first evidence suggesting that adults could grow new neurons (a process called neurogenesis) was presented in the 1960’s by Joseph Altman, who showed growth of neurons in adult rats, but these findings were generally not accepted. In the 1980’s, it was shown again that adult neurogenesis exists in rats and in birds and this set off a frenzy of research, resulting in the scientific field of neurogenesis being recognised, currently one of the hottest topics in neuroscience.
In the early 90’s, neural stem cells were identified, self-renewing cells from which new neurones are generated. In 1998 it was shown that the human hippocampus (an area of the brain involved in learning and the formation of memories), retains its ability to generate neurons throughout life and in 1999 this was shown again in adult monkeys. Recent evidence suggests that new neurons are produced throughout life in two specific areas of the brain, although probably only in numbers sufficient to replace those that gradually die and this ability decreases with age.
Recently it has been discovered that some types of anti-depressant can actually increase neurogenesis by increasing levels of a chemical called norepinephrine. The next era in this exciting field will uncover what causes neurones in the adult brain to grow, how this is regulated, how new neurones become functional and why neurones in most areas of the brain do not regenerate. Also, very important insights into new strategies for treatment of injury, degenerative neurological disorders such as Alzheimer’s and Parkinson’s disease and psychiatric disorders could emerge.