A region in the pons just ventral of the locus coeruleus that triggers REM sleep. One of its jobs is to inhibit motor neurons. It does this via Glutamatergic neurons that excite neurons in the medulla, which projects axons down the spinal cord to release GABA and glycine to inhibit spinal motor neurons. Hence the flaccid muscles during REM sleep. Lesions to this area can abolish the loss of muscle tone in REM sleep, leading to acting out dreams.