Does the Adult Brain Really Grow New Neurons?

This article discusses the idea that neurogenesis, one of the greatest neuroscience discoveries of the last 20 years, may not be as accurate as we thought it might be.  Neurogenesis is the ability of the new neuron cells to be created, which enhances memory and mood regulation. A study performed and reported in the online Nature International Journal of Science reports that adults produce no new cells in the hippocampus, a vital part of the brain that is involved in processing memories. 

It was originally believed that brain cell growth ceased shortly after birth, but studies performed on adult rats, mice, birds, and monkeys showed new brain cell development.  Later, it was found that the human brain also produces new brain cells, around 1,400 everyday.  However, a new study performed by Arturo Alvarez-Buylla shows the complete absence of new brain cells in the adult brain.  This study examined 59 human brain samples ranging from fetal to 77 years.  Brain tissue was treated with antibodies that would signal the presence of young neurons as well as dividing cells. In the prenatal and neonatal samples, they found evidence of young and developing brain cells, however, in brain tissue of 7 years to 13 years, the amount of these cells dropped dramatically, and in adults there was no evidence at all of any new brain cells. 

Jonas Frisen, the author of the study that found the development of 1,400 new brain cells every day says that looking for young neurons is a difficult thing to do, especially when considering the fact that there are tens of millions of hippocampal cells in the brain.  It is such a small fraction of total cells and the results could possibly be skewed. 

There is still a lot of debate on whether or not neurogenesis occurs, and if so, to what extent.  The study is still new and it is believed to be too early to be widely accepted.  

I found this article to be very interesting.  I have read articles in the past that talk about neurogenesis and I was under the impression that this concept is scientific fact.  After reading this article, I have unresolved questions about whether or not neurogenesis occurs.  The only doubt that I have that based off of this article is the fact there is claimed to be 1,400 new brain cells created each day when compared to the tens of millions of brain cells that exist.  I wonder how much brain tissue was tested in this experiment.  If it was a small sample, I believe that further tests would need to be conducted to test a larger tissue size or multiple smaller samples.