"Certain genes and proteins that promote growth and development of embryos also play a surprising role in sending chemical signals that help adults learn, remember, forget and perhaps become addicted, University of Utah biologists have discovered. "We found that these molecules and signaling pathways [named Wnt] do not retire after development of the organism, but have a new and surprising role in the adult. They are called back to action to change the properties of the nervous system in response to experience," (...) "Almost certainly what we have discovered is going on in our brain as well," (...)" - Amira

"Synapse Plasticity is the Basis of Learning and Memory (...) Proteins known as receptors are delivered to the synapses or removed from them to strengthen or weaken the connection. (...) The Wnt signaling identified in the new study "tells the depot to put more receptors into the synapse -- or not," (...) By crippling various genes in the worms, the researchers identified the "signaling pathway" by which a Wnt protein in one nerve cell sends a chemical signal to another cell telling it to increase the number of receptors on its surface, thus increasing the strength or volume of nerve signals between the cells. (...) "Addiction is like learning at a primitive level," Maricq says. "Addiction means that somewhere in your brain, synapses are too strong. So you want more." - Amira