Brainstem neurons responsible for postural, masseter or pharyngeal muscle atonia during paradoxical sleep in freely-moving cats

Abstract

In this review, we will describe our findings regarding the brainstem neurons responsible for the postural, masseter, or pharyngeal muscle atonia observed during paradoxical sleep (PS) in freely moving cats. Our study suggests the existence of multiple slow conducting and fast conducting systems in the brainstem that control the activity of spinal and orofacial motoneurons across wake-sleep states. We propose that the PS/atonia-on neurons, characterized by their very slow conduction and location in the peri-locus coeruleus alpha (peri-LCa) and adjacent LCa of the mediodorsal pontine tegmentum, play a critical executive role in the somatic and orofacial muscle atonia observed during PS. Slow conducting medullary PS/atonia-on neurons located in the nuclei reticularis magnocellularis (Mc) and parvocellularis (Pc) may play a critical executive role in the generation of, respectively, antigravity or orofacial muscle atonia during PS. In addition, either tonic or phasic cessation of activity of medullary serotonergic neurons may play an important role in the atonia of genioglossus muscles during PS via a mechanism of disfacilitation.