In the future, say researchers, it may be possible that these stem cells can be stimulated to grow even more, perhaps helping to rewire the brain and help stroke survivors recover lost memory function.

Stem cells are important in the formative stages of brain development. Researchers say stem cells help form neurons, which mature and make the complex circuits that enable the brain to perform its many functions. Stem cells are present in the embryonic brain and remain in the brain throughout life, says Sharp. Most stem cells are located next to the ventricles in the brain and in the hippocampus.

Stem cells are present in the brain throughout life, and Sharp says there is evidence in rodents that the numbers of stem cells and newly formed neurons decreases as the brain ages.

For stroke survivors, recovering speech or motor skills typically requires many years of speech and physical therapy. Sharp cautions that more research is needed to determine whether or not sparking the growth of stem cells can be used as a companion treatment along with current types of therapy.

"The fact of the matter is, after stroke of all types, memory function is frequently impaired," says Sharp. "Though memory function often recovers to at least some extent, the mechanism by which this recovery occurs is not known. The birth of new neurons could very well be the mechanism which leads to memory recovery after ischemia."

Following the blockage of blood flow and decreased oxygen and glucose delivery to the brain -- a condition known as ischemia -- researchers found a 12-fold increase in the birth of new cells in the dentate gyrus of the hippocampus, a region of the temporal lobe that is crucial in laying down all long term memories. Sharp says that following the ischemia, half of the newborn cells become neuro
'"/>

Contact: Brian Henry or Cathy Yarbrough
615-231-1601
American Heart Association
5-Feb-1999