Memory aside, the scientists wanted to see whether the transgenic mice actually learned more effectively. To find out, they reconditioned the animals to be frightened by a mild shock or tone in a certain chamber. Then they removed the shocks and sounds and put the mice back into the same chamber. Although the Doogies became more panicky at first--consistent with the previous testing--they also calmed down sooner and resumed normal behavior. In other words, they were quicker to grasp the change.
The tests confirm that many different brain systems--processing such varied information as sights, sounds and touches--all use a common biochemical pathway, involving NMDA receptors, for learning, an idea first put forth by Donald O. Hebb in 1949. They further prove the often debated theory, called Long Term Potentiation (LTP), that memories arise when two neurons form a lasting connection. Tsien's work "is one of the best pieces of evidence so far" for LTP, says Charles Stevens of the Salk Institute. "[It] is the first study so far to produce a positive effect, and that's why it's so good."
Perhaps most dramatic, the results show that it is possible to make animals more or less intelligent by tweaking their genes. Humans possess a corresponding gene, although its impact on behavior is as yet unexplored. "It's very exciting and holds the hope of not only making animals smarter, but also, ultimately of having a gene therapy for use in areas such as dementia," says Ira Black of Rutgers University. "This is far in the future and is certainly not something we oculd bring to the bedside tomorrow." But maybe in a decade.