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A Century Searching for the Neurons Necessary for Wakefulness
Journal article   Open access   Peer reviewed

A Century Searching for the Neurons Necessary for Wakefulness

Fillan S. Grady, Aaron D. Boes and Joel C. Geerling
Frontiers in neuroscience, Vol.16, 930514
07/01/2022
DOI: 10.3389/fnins.2022.930514
PMCID: PMC9344068
PMID: 35928009
url
https://doi.org/10.3389/fnins.2022.930514View
Published (Version of record) Open Access

Abstract

Wakefulness is necessary for consciousness, and impaired wakefulness is a symptom of many diseases. The neural circuits that maintain wakefulness remain incompletely understood, as do the mechanisms of impaired consciousness in many patients. In contrast to the influential concept of a diffuse “reticular activating system,” the past century of neuroscience research has identified a focal region of the upper brainstem that, when damaged, causes coma. This region contains diverse neuronal populations with different axonal projections, neurotransmitters, and genetic identities. Activating some of these populations promotes wakefulness, but it remains unclear which specific neurons are necessary for sustaining consciousness. In parallel, pharmacological evidence has indicated a role for special neurotransmitters, including hypocretin/orexin, histamine, norepinephrine, serotonin, dopamine, adenosine and acetylcholine. However, genetically targeted experiments have indicated that none of these neurotransmitters or the neurons producing them are individually necessary for maintaining wakefulness. In this review, we emphasize the need to determine the specific subset of brainstem neurons necessary for maintaining arousal. Accomplishing this will enable more precise mapping of wakefulness circuitry, which will be useful in developing therapies for patients with coma and other disorders of arousal.
arousal ascending reticular activating system brainstem coma wakefulness

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