Dynamical Systems in Neuroscience:

338 Simple Models(a)stellate cellof entorhinalcortexsimple model-60 mVsag15 mV1 sec-500 pA 100 pA 165 pA 200 pA(b)stellate cell of entorhinal cortexsimple modelI=173 pAI=170 pAI=167 pAI=165 pA(c)recovery variable, u20016012080separatrixspikespikesI=165 pA limit cycleI=173 pAattractor-60 -55 -50 -45 -40 -35-60 -55 -50 -45 -40 -35membrane potential, V (mV)membrane potential, V (mV)Figure 8.39: Comparison of in vitro recordings of stellate neurons of rat’s entorhinalcortex with simulations of the simple model 200 ˙v = 0.75(v + 60)(v + 45) − u + I,˙u = 0.01{15(v + 60) − u}, if v ≥ 30, then v ← −50. (a) Responses to steps of dccurrent.(b) Subthreshold oscillations and occasional spikes at various levels of injecteddc-current. (c) Phase portraits corresponding to two levels of injected dc-current. Weaknoise was added to simulations to unmask subthreshold oscillations. (Data were kindlyprovided by Brian Burton and John A. White. All recordings are from the same neuronexcept steps of −500 pA and 200 pA were recorded from a different neuron. Spikes arecut at 0 mV.)