Kathy I went searching and read some interesting stuff about the production of new brain cells. This isn't the only thing I found but thought this might tie in with what you are saying:
New brain cells die without a job to do
16 August 2006
Magazine issue 2565. Subscribe and save
Pictures of spreads from New Scientist magazine
When it comes to brainpower they say you either use it or lose it. Now a study in mice suggests that the survival of newly formed adult brain cells depends on the amount of input they receive.
Fred Gage of the Salk Institute for Biological Studies in La Jolla, California, and his colleagues infected genetically engineered mice with a virus that stops new brain cells from producing NMDA receptors - proteins that sit on the surface of brain cells and help them communicate with each other. The virus used infects only newly generated cells, leaving other cells untouched.
Infected cells that lacked NMDA receptors died sooner than their normal counterparts, suggesting that communication is essential for survival (Nature, DOI: 10.1038/nature05028).
To confirm this the researchers injected some of the virus-infected mice with a compound that blocks all NMDA receptors. They found this increased the survival rate of the brain cells ...http://www.newscientist.com/article/mg19125655.000-new-brain-cells-die-without-a-job-to-do.html