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. Author manuscript; available in PMC: 2022 Jul 18.
Published in final edited form as: Cell Rep. 2022 Jul 5;40(1):111028. doi: 10.1016/j.celrep.2022.111028

Figure 3. Retrosplenial splines demarcate high-activity REM sleep frames.

Figure 3.

(A) Features used to classify cells into putative fast-spiking (FS) and regular-spiking (RS) clusters using a Gaussian mixture model. P25Width is the width of the waveform at 25% of the peak amplitude. The color bar shows the posterior probability of a cell being classified as an RS cell. Thus, red dots represent putative RS cells and blue dots represent putative FS cells.

(B) Firing rates (normalized to awake firing rate) of FS and RS cells across CA1, RSC, and V1 across sleep/wake states. RSC FS cells fired at significantly higher rates during REM compared with NREM or awake states.

(C) Raster plot of FS and RS cells from RSC and CA1 during a single REM epoch (top), with average firing rate of each cell type plotted below. Gray dashed lines represent peaks of RSC theta cycles with splines. Theta cycles with splines cluster together into frames and the firing rates of retrosplenial FS and RS cells increase during the spline-rich frames.

(D) Probability of observing RSC theta cycles with splines triggered off theta cycles with (green) or without (black) splines across three rats from which single units were recorded during REM sleep. When theta cycle 0 contains splines, the probability of observing additional theta cycles with splines remains elevated for −22 to +22 theta cycles before and after theta cycle 0 (black bars show theta cycles with effect size ≥0.5).

(E) (Left) Peristimulus time histogram (PSTH) of representative RSC FS cell triggered at the peak of RSC theta cycles with (dark green bars) and without (light green line plot) splines. Spline-triggered averages show sustained increases in both the rate and theta modulation of FS firing. (Right) Similar plot, now shown for a CA1 FS cell firing, again triggered at the peak of RSC theta cycles with (purple bars) and without (gray line plot) splines. The CA1 FS cell also shows sustained increases in firing rate around splines.

(F) Correlation between firing rate and RSC spline power for the same RSC and CA1 FS cells shown in (E).

(G) Normalized firing rate of FS cells for RSC (left) and CA1 (right) across ±30 theta cycles centered on theta cycles with (green bars for RSC; purple for CA1) and without (gray bars) RSC splines. The cycles where the effect size was ≥0.5 are marked by black bars. FS cells in both RSC and CA1 showed sustained increases in firing rates during the high-activity REM frames demarcated by RSC splines.

(H) Same as (G) but for RS cells. RS cells in both RSC and CA1 showed sustained increases in firing rates during the high-activity REM frames demarcated by RSC splines.