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Sleep and wakefulness is stabilized by a population of orexin-expressing neurons. In this study, the authors demonstrate how these neurons drive arousal by silencing sleep-promoting neurons in the ventrolateral preoptic nucleus.

The dorsal pons in the brainstem is packed with clusters of neurons, including the parabrachial nucleus, that are involved in many vital functions. Here, authors use single nucleus RNA sequencing and MERFISH to create a spatially defined transcriptional atlas of this region.

Dorsal raphe 5HT(DR^Sert) neurons regulate arousal from hypercapnia by their projections to the neurons in the external lateral parabrachial nucleus (PBel) that are glutamatergic and also express calcitonin gene related peptide (PBel^CGRP). The DR^Sert input to the PBel modulates the arousal system to rising levels of blood CO₂, and may be mediated by 5HT_2a receptors on the PBel^CGRP neurons.

The mammalian basal forebrain controls cortical rhythm and wake-sleep. Anaclet et al.use genetically-targeted chemogenetic systems to activate or inhibit cholinergic, glutamatergic or GABAergic neurons in this region, and reveal their contributions to behavioral and electrocortical arousal in behaving mice.

Anatomical lesions of the preoptic area (POA) can cause sleep loss while electrical, chemical, or thermal stimulation of POA can induce sleep. To better understand the exact neural function of the POA, this study shows that galanin and GABA+ inhibitory neurons in the ventrolateral POA that project to the wake-promoting tuberomammillary nucleus promote sleep in a stimulation frequency dependent manner.

Cell groups in the hypothalamic suprachiasmatic clock contribute to the genesis of circadian rhythms. The authors identified two populations of vasoactive intestinal polypeptide-expressing neurons in the suprachiasmatic nucleus which regulate locomotor circadian rhythm in mice.

Supramammillary nucleus (SuM) neurons have been studied in the context of REM sleep but their possible role in mediating wakefulness is not known. Here the authors elucidate the distinct functional contributions of three subpopulations in the SuM on electrographical and behavioral arousal in mice using genetically targeted approaches.

Using a combination of targeted activation and optogenetic-based mapping in mice, this study demonstrates that sleep-active GABAergic neurons in the medullary parafacial zone promote slow wave sleep and cortical slow wave activity and uncovers functional circuit connections linking these neurons with the cortex.