Aa, an example of EPSP–IPSP sequences in response to thalamic stimulations recorded at −70 and −45 mV. Ab, recordings in the red square in Aa are shown expanded. To identify the onset of IPSP over EPSP, the first derivative (dV/dt) of the membrane voltage at the onset region was calculated, then the zero crossing of the dV/dt curve was defined as the onset of IPSP, as shown by an arrow. B, distribution for the temporal difference between the onset of thalamic EPSPs and fast IPSPs.