Scientists Uncover Two Possible Roles of Adult Neurogenesis

Author:  Tetyana Pekar
Institution:  University of Toronto
Date:  October 2008

The controversy over the exact role of adult neurogenesis has been settled claims a study published in this month's Nature Neuroscience. A team of researchers, led by Itaru Imayoshi at the Institute of Virus Research in Kyoto University, has shown the strikingly different roles that new cells play in the two brain regions where adult neurogenesis occurs. These findings could help lead the way to new treatments for patients with brain damage or neurodegenerative diseases.

In the last decade, research has shown that new cells can be readily created in the brain and populate regions of the olfactory bulb and the hippocampus, a region important for memory formation. These findings have overturned the long-held belief that neurogenesis does not occur in the adult brain.

However, the importance and magnitude of hippocampal neurogenesis has remained obscure. A recent study led by Dr. Paul Frankland reported that new born cells are preferentially incorporated into hippocampal memory networks during spatial learning tasks. However, others have reported no memory deficits in mice when hippocampal neurogenesis was abolished.

In this definitive study, Imayoshi and colleagues used innovative genetic methods to selectively kill newly born cells as soon as they differentiated into neurons. They showed that neurogenesis is essential for the maintenance of cells in the olfactory bulb, but is not required for the development of odor-associated memory. By contrast, ablation of newly born neurons impairs spatial memory in the hippocampus, suggesting that neurogenesis in this region adds new neurons and contributes to memory formation throughout life, and is not related solely to tissue maintenance as it is in the olfactory bulb.

"Together with previous work, this study provides us with clear evidence for the importance of adult neurogenesis in the normal adult brain," wrote Drs. Frankland and Miller in the accompanying news article. Concluding that adult neurogenesis in the hippocampus is "required for neuronal addition and hippocampal growth, thereby potentially contributing to the ability to accumulate new memories throughout life."

The next question is how this unique population of cells can be utilized in neural repair, regeneration or even in the enhancement of learning and memory in healthy individuals.

Written by: Tetyana Pekar

Edited by: Akshar Patel and Matthew Getz

Published by: Hoi See Tsao