Our knowledge of how specific neurons are recruited in active ensembles that define the brain response to a particular behavioural experience is still limited. In order to investigate the mechanisms underlying these processes it is essential to identify which cells within the network experience behaviourally driven alterations in synaptic activity levels. Here, we used two different approaches based on Immediate-early genes (IEG), whose expression levels are tightly controlled by neuronal activity, to label synaptically activated cells in the hippocampus...