Present address: UCLA Medical Center, Departments of Neurobiology, Psychiatry and Psychology, 695 Charles Young Drive South, Los Angeles, CA 90095, USA.
Paradoxical effects of learning the Morris water maze on adult hippocampal neurogenesis in mice may be explained by a combination of stress and physical activity
Article first published online: 18 MAR 2005
Genes, Brain and Behavior
Volume 5, Issue 1, pages 29–39, February 2006
How to Cite
Ehninger, D. and Kempermann, G. (2006), Paradoxical effects of learning the Morris water maze on adult hippocampal neurogenesis in mice may be explained by a combination of stress and physical activity. Genes, Brain and Behavior, 5: 29–39. doi: 10.1111/j.1601-183X.2005.00129.x
- Issue published online: 25 JUL 2005
- Article first published online: 18 MAR 2005
- Received 18 November 2004, revised 20 January 2005, accepted for publication 31 January 2005
- progenitor cell;
- spatial learning;
- stem cell
Studies in rats that assessed the relation of hippocampus-dependent learning and adult hippocampal neurogenesis suggested a direct regulatory effect of learning on neurogenesis, whereas a similar study in mice had not found such causal link. We here report a substantial decrease of BrdU-positive cells and other measures of adult hippocampal neurogenesis in mice trained in the hidden (HID) or cued version (VIS) of the Morris water maze as compared to untrained animals (CTR). Particularly, cells on advanced stages of neuronal development contributed to this decrease, whereas earlier progenitors (type 2 cells) were not diminished in HID, but were diminished in VIS as compared to CTR. The differential regulation of type 2 cells in HID and VIS may have been caused by a different degree of physical activity, given that a time-yoked control group did not differ from HID, and type 2 cells reportedly constitute the proliferative dentate gyrus population that primarily responds to physical activity. The decrease of hippocampal neurogenesis by water maze training was reversible by pre-exposing animals to the water maze prior to training, suggesting that stress associated with training may have caused the acute downregulation of adult neurogenesis. We propose that in mice the Morris water maze does not provide a pure enough learning stimulus to study the presumed effects of ‘learning’ on adult neurogenesis. In addition, however, our data show that physical activity that is intricately linked to many cognitive tasks in rodents might play an important role in explaining effects of learning on cellular hippocampal plasticity.