Figure 1. Carbachol-elicited REM sleep-like episodes.

A, a typical REM sleep-like episode elicited by pontine carbachol (10 nl) injection into the dorsomedial pontine tegmentum. The episodes last 2–4 min and include activation of the cortical EEG, the appearance of theta-like activity in the hippocampus, suppression of XII nerve activity and slowing of the central respiratory rhythm. The two bottom traces are composed of discrete points that represent the peaks of the moving average of XII nerve activity and instantaneous respiratory rate, respectively, measured in successive respiratory cycles. B, distribution of the sites of carbachol injections made in this study. The centres of the injection sites are superimposed on the closest standard cross-sections from a rat brain atlas (Paxinos & Watson, 1991). Abbreviations: CnF, cuneiform nucleus; KF, Kölliker–Fuse nucleus; LDT, laterodorsal tegmental nucleus; Mo5, trigeminal motor nucleus; PnO, nucleus pontis oralis; scp, superior cerebellar peduncle; VT, ventral tegmental nucleus.