How chicks make memories: the cellular cascade from c-fos to dendritic remodelling.

Training chicks on a one-trial passive avoidance task results in a cellular cascade over the subsequent hours. Phosphorylation of the presynaptic phosphokinase C substrate B-50 is followed by immediate-early gene expression and increased synthesis of pre- and postsynaptic glycoproteins, increases in dendritic spine densities, synapse and synaptic vesicle numbers, and a prolonged increase in neuronal bursting. Many of these effects have been localized to two forebrain regions: the left intermediate medial hyperstriatum ventrale and the lobus parolfactorius. Pretraining lesions in the left intermediate medial hyperstriatum ventrale, or post-training lesions in the lobus parolfactorius result in amnesia. These and related results lead to models of memory storage based on multiple representation by way of synaptic stabilization through glycoprotein synaptic recognition molecules.