Fig. 4
From: Similarities and differences between natural sleep and urethane anesthesia
Slow oscillations at cortical surface and deep layers and their unit modulation differ between dU and NREM. (A) Current-source density (CSD) of δ (1.5–4.5 Hz) at the surface (surf, left) and deep (right) parietal cortex (PAC) during dU in one representative animal. The superimposed traces show the averaged δ-filtered LFP at the corresponding depth, centered on the δ peaks detected at either the surface (left) or deep PAC (right). Note the large δ amplitude at the surface, the polarity reversal in the upper layers, and the smaller amplitude in deeper layers. Also note the strong sinks and sources in the upper layers, strongest for surface δ peaks and less pronounced for deep δ peaks. (B) CSD of surface and deep δ waves in PAC during natural NREM sleep in another animal. Note the five times smaller scale of the superimposed δ-filtered LFPs, and the tenfold weaker sinks and sources, with the strongest located in deeper layers. (C) Peri-event histogram (PEH) of normalized (norm., see Methods) multi-unit activity (MUA) at 0.4 mm depth centered on surface δ peaks (left) and deep δ peaks (right) during dU for the same animal as in A. Note the weaker MUA modulation by deep δ waves. (D) PEH of norm. MUA at 0.3 mm depth centered on surface δ peaks (left) and deep δ peaks (right) during NREM for the same animal as in B. The corresponding δ waves in C and D are shown. Note the large difference in MUA modulation by δ between dU and NREM, as well as the opposite amplitude relationship of surface and deep δ waves in dU (highest at the surface) and NREM (highest in deeper layers).
