Figure 3.

Inhibition balances excitation in the baseline as well as in the persistent state. A, Input currents into an excitatory neuron. Red, Excitatory input (recurrent plus background). Blue, Inhibitory input. Black, Total input (excitatory plus inhibitory). The firing rate and the CV of the ISI histogram of this neuron are as follows: baseline: f = 1.4 Hz, CV = 1.2; delay: f = 16.6 Hz, CV = 1.9. B, Population histograms of the inputs into the neurons normalized to the firing threshold. Blue, Time-averaged inhibitory input. Red, Time-averaged excitatory input. Black, Time-averaged total input. Green, Time-averaged total input plus 1.5 SDs of the total input fluctuations. All neurons are included in the histograms. Vertical line corresponds to threshold. C, Population histograms of the membrane potentials. Red, Excitatory population. Blue, Inhibitory population. The membrane potentials of all the neurons are included in the histograms. The potentials are sampled with a rate of 0.1 Hz. Vertical line corresponds to threshold. D, Spike trains of 200 excitatory neurons during baseline and delay periods. E, CV versus firing rates. One thousand neurons in each population are included. The histograms of the CVs and the firing rates are plotted in Figure 4. The results plotted in C and D were obtained in simulations 100 s long.