The fact that the flies continued to show a learned response even after the new synaptic activity waned suggests that other memory traces found at higher levels in the brain took over to encode the memory for a longer period of time, Dr. Davis suggests.  If so, the rapid changes of nerve transmission that the researchers saw may be the all-important switch that initiates the formation of new memories. 

This research suggests a previously unknown mechanism for how memories are formed, Dr. Davis says.  While this study looked only at learning related to odors, this newly identified process may be at work in many other kinds of learning as well.  It is likely that these or similar mechanisms are important for memory in humans and other animals, he adds.

"This is a remarkable study which uses molecular genetic approaches to visualize memory formation in a living organism.  It demonstrates that, in this model system, short term memory involves the recruitment of new synaptic connections into pre-existing ensembles of synapses.  It will be critical to determine whether similar principles control memory formation in higher organisms," says Robert Finkelstein, Ph.D a program director at NINDS.

The researchers now plan to put fluorescent genes into a variety of other neurons of the brain in order to determine which ones respond to different kinds of stimuli. This will allow them to learn how the changes they identified affect higher-level neurons. They also hope to begin studying similar mechanisms in other animal models, such as mice.

The NINDS is a component of the National Institutes of Health within the Department of Health and Human Services and is the nation's primary supporter of biomedical research on the brain and nervous system. ninds.nih