In Figure 6, we show how mean firing rate clamping can be achieved even during gross manipulation of network connectivity using different synaptic blockers, but unsurprisingly, the short time-scale features of population firing activity are greatly affected by these perturbations even though mean firing levels are maintained.
Specifically, we make it clear that currently our method only controls the mean network firing level.
Synaptic blockade strongly affected mean spontaneous firing levels (CNQX: −74.2%, AP5: −66.6%, bicuculine: +357%) and network-level signal propagation.
In control animals, this fraction was initially constant as the stimulation intensity decreased, even at levels where mean firing rates had modestly diminished.
Spike frequency adaptation index was quantified as the relative decrease in instantaneous firing frequency during a 1-s long depolarizing current step (from −65 mV holding level) during which the mean firing frequency was ∼25 Hz.
The initial (approximately 10 hours) periods of suppressed network synchrony were not accompanied by reductions in mean firing rates as compared to pre-ACh applications levels, indicating that Sync Ratio values can change independently of changes in firing rates (compare Figure 3c and d).
Reponses for each cell were normalized to baseline firing rate by calculating a Z-score (Z = (Ri-Rm)/S.D ., where Ri = firing rate at an individual time point and Rm = mean firing rate, S.D. = standard deviation of the mean firing rate.
We ask whether mean firing rates at the two temperatures are different, separately analyzed for each sound intensity level (supplement to Figure 1).
By 40 min, the mean firing rate of tested neurons increased to 24.7 ± 4.0 spikes/s (N = 11); this value was significantly higher than the level prior to formalin administration (P = 0.004, Wilcoxon signed rank test) and exceeded the firing frequency of saline-treated units (6.6 ± 1.4 spikes/s, N = 10, P < 0.0001, U = 4.0, Mann–Whitney Wilcoxon test; Fig. 3a).
Mean spontaneous activity was subtracted from mean firing rates.
