Matching ISI distributions from oxytocin neurons in vitro.

Neurons recorded in vitro (redrawn from [6]), stimulated by a constant depolarising current, show a much narrower ISI distribution, indicating a more regular spiking rate, much closer to a normal distribution than observed in vivo (Fig 1). The remaining variability can be attributed to membrane noise, or some low level of residual synaptic input. Using the same HH and IF models, with parameters fitted to the in vivo reference data, we were able to match the in vitro ISI distribution using a constant applied input combined with a low rate of low magnitude excitatory synaptic input. In the HH model (red) we used a 4.5 nA constant input with EPSC parameters Δepsc = 0.008 and Repsc = 120 Hz, producing 5.3 spikes/s. In the IF model we used Vext = 20.3 mV with EPSP parameters Ire = 120 Hz and eh = 0.08 mV, and Iratio = 0. The cluster plots indicate that ISIs are independent of the preceding ISI.