Figure 2. Simulated intrinsic cortical activity and the properties of the neuronal firing activities.
(a) A snapshot of the activities. On the left, the red (black) dots indicate the spikes of the excitatory (inhibitory) neurons. On the right, the colours represent the mean firing rates. (b) Spike rasters from one brain area. (c) Example time courses of the membrane potentials of the excitatory and inhibitory neurons. (d) Firing rate distributions. The mean firing rates of the excitatory neurons were low (1.2 Hz). The distributions of the firing rates conformed to lognormal distributions (R2 = 0.97 for excitatory; R2 = 0.98 for inhibitory; P < 10−20). (e) Coefficient of variation of the inter-spike intervals. The averages were 1.00 and 0.95 for the excitatory and inhibitory neurons, respectively, which indicated that the spike trains were highly irregular and followed a Poisson distribution. (f) Relationship of the firing rates between the excitatory and inhibitory neurons (r = 0.86; P < 10−20). (g) Membrane potential distributions. The average membrane potentials were −64.3 mV and −57.6 mV for single excitatory and inhibitory neurons, respectively. These average potentials were high compared with the resting potentials (−70 mV). (b–e,g) Red and black represent the excitatory and inhibitory neurons, respectively.