the first line of defense against any kind of brain damage or injury--are much more active in the normal brain than previously thought. For the first time, scientists have been able to observe the behavior of the cells in the intact brain and they have found that during so-called resting stages, the cells were in fact continually interacting with neurons and other brain cells. This persistent interaction, the researchers say, may figure importantly in maintaining normal brain function. The findings appear in the current issue of Science.