Fig 8: Characterization of thalamocortical evoked spiking in visual cortex between behavioral states and its stability across sleep and wake

(A) Heat plot response of the firing rate of each cell isolated during stimulation. Data are grouped by layer, and sorted by the magnitude of response within each layer. N = 45 cells, 4 animals. (B) Evoked spikes per stimulation for each of the 4 vigilance states. The y axis represents the average number of evoked spikes for a single stimulation, calculated as spikes in a 15 ms post stimulus window, minus the expected number of baseline spikes in that window; each dot represents a cell. Evoked spikes varied significantly by vigilance state (AW-QW, p=3.4e-4; AW-NREM, p=6.56e-4; AW-REM, p=4.70e-4; QW-NREM, p=0.0022; QW-REM, p=0.0122; NREM-REM, p=0.0380). (C) To determine whether evoked spike rates were affected by time spent awake or asleep, we compared evoked spiking before and after a sleep or wake dense epoch, using a >75% time in state threshold, as for fEPSPs in Figure 7. Hypnograms show examples of wake or sleep dense epochs with flanking periods of the opposite state. Gray rectangles indicate the stimulation times chosen for the analysis. (D) example raster plots and post-stimulus time histograms of firing rate for an example cell pre-post sleep. (E) Shows the number of evoked spikes before and after wake (left) or sleep (right) dense epochs; each dot is one cell, averaged across all of the wake or sleep dense epochs (wake dense n = 32 cells, 4 animals; sleep dense n = 24 cells, 4 animals). (F) Correlative plot of duration of wake dense epoch against change in evoked spikes; each dot represents the response of a single cell to a single epoch (post – pre). Black line = linear fit; R2 value and p value included on plot. Inset is an expansion of plot between 0.25-3.5 hours. (G) Same as (F) but for sleep dense epochs. N = 35 wake dense epochs, 50 sleep dense epochs, 4 animals.