Raster plots from putative hippocampal neurons recorded in consecutive days from the same microwire. The left panel shows responses to Anfield (Liverpool FC stadium). Although the responses seem to be stable across days, the waveforms associated to these neurons are very different. Therefore, without tracking the neural activity over the whole time between sessions, it would be hard to argue whether it is the same neuron or a different one from the network coding the concept “Anfield”. The right panel shows responses to Stonehenge on consecutive days. In this case, a sparse neuron in the first session leads to a very selective response. In the next session, the response seems to be maintained, but its selectivity is not the same. Tracking the activity would allow us to distinguish between a sorting error (the cluster associated to the neuron being contaminated by spikes from other neurons) and an actual change in selectivity.