Abstract
Neurons are typically classified according to their intrinsic firing patterns and distinctive morphological features. However, we found that the in vitro patterns of neuronsin the CA3 field of the rat hippocampus change very significantly following a short period of low frequency subthreshold stimulation of their afferents. This effect could be reproduced by intrasomatic current pulses and was blocked by kinase inhibitors. Cluster analysis of the firing patterns before and after conditioning revealed systematic transitions towards adapting and intrinsic burst behaviours, irrespective of the initial pattern exhibited by the cell. Using a conductance-based model, we demonstrate that the observed transitions can be mediated by recruitment of calcium and M-type potassium conductances. We conclude that CA3 neurons adapt their conductance profile to the statistics of ongoing activity in their embedding circuits, making their intrinsic firing pattern not a constant signature, but rather the reflection of long-term circuit activity.