Figure 2.
VPM Firing Correlates with Cortical Down-State Duration and PV Firing in Down States
(A) Duration of cortical down states associated with detected VPM activity (VPM-active) and VPM inactivity (VPM-silent; p = 4.5E−7; one-tailed paired Student’s t test; n = 18 recordings from 7 animals).
(B) VPM spike count in PV-active and PV-silent cortical down states (p = 2.5E−4; one-tailed Wilcoxon signed rank test; n = 18 cells in 7 animals).
(C) Spike-triggered VPM IFR based on the timing of PV spikes recorded during cortical down states for one representative recording (Gaussian kernel SD, 12.5 ms; the thick black line indicates the mean; the shaded area the SEM). The VPM IFR triggered by “surrogate” spikes is displayed with the thick gray line. Dotted gray lines indicate the 5th and 95th percentiles of the distribution of the mean surrogate spike-triggered VPM IFR (100 surrogates).
(D) Z scores in the pre- and post-time windows of the PV-spike-triggered VPM mean firing rate with respect to surrogate data: 10 out of 18 recordings showed a significant difference between actual and surrogate data in the pre-spike window (one-tailed z-test). The dashed line indicates significance at p = 0.05. Cells with Z scores corresponding to p > 0.05 lie above the dashed line and are marked with asterisks in Figure S2.
(E) Mean firing rate of the VPM before and after PV spikes in down states (pre: [−100, 0] ms; post: [0, 100 ms]; mean ± SEM; p = 3E−4; two-sided Wilcoxon signed rank test; n = 116 spikes for the same recording as in C).
(F) Variation of VPM mean firing rate relative to the overall mean surrogate firing rate in the pre- and post- windows (p = 0.032; one-tailed Student’s t test; n = 10 cells from 6 animals) for those cells showing a firing rate significantly higher than that of the surrogate data.
See also Figure S2.