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. Author manuscript; available in PMC: 2020 Feb 6.
Published in final edited form as: Neurosci Lett. 2018 Jan 31;693:19–28. doi: 10.1016/j.neulet.2018.01.042

TABLE 1.

Brain regions proposed to be involved in wakeful arousal (the Ascendinga Arousal Systemb)

Brain region involved in maintaing wakefulness Main neurotransmitter/neuro modulator Involved Name originally given to the arousal system Other Function
Brainstem:
Mesopontine reticular formation nuclei [26]:
 -Mesencephalic reticular formation
 -Cuneiform nucleus
 -Pontine reticular nucleus, oral part		 Glutamate Ascending reticular activating system Coordination of autonomic/motor/sensory brainstem nuclei [29]
Pontomedullary reticular formation nuclei [24]:
 -Pontine reticular nucleus, caudal part-
 Gigantocellular reticular nucleus
 -Parvicellular reticular nucleus
 -Subnucleus reticularis dorsalis		 Serotonin
Adrenaline
Norepinephrine		 Ascending reticular activating system Coordination of autonomic/motor/sensory brainstem nuclei [29]
Mesopontine tegmental nuclei [24,27–28]:
 -Pedunculotegmental nucleus
 -Laterodorsal tegmental nucleus		 Acetylcholine Diffuse neuromodulatory system Locomotor, Limbic [29]
Raphe nuclei [24,27–28]:
 -Median raphe
 -Dorsal raphe
 -Raphe pallidus
 -Raphe obscurus		 Serotonin Diffuse neuromodulatory system Nociception, Limbic, Temperature regulation, Blood pressure control, Memory, Motor [29]
Locus coeruleus [24,27–28] Norepinephrine Diffuse neuromodulatory system Autonomic, Attention, Memory, Motivation [29]
Ventral tegmental area [12, 24, 44] Dopamine Diffuse neuromodulatory system Attention, Memory, Reward, Drug abuse, Motivation [29]
Parabrachial nuclei [11,33,27,28] Glutamate – Autonomic, Limbic, Viscerosensory [29]
Subcoeruleus area [11,28] Glutamate – Limbic, Motor [29]
Periaqueductal gray, ventrolateral part [24,28] Dopamine – Autonomic, Limbic [29]
Solitary nucleus [24] Glutamate – Viscerosensory Autonomic [29]
Hypothalamus:
 - Tuberomamillary nucleus [27,28] Histamine – Temperature regulation Endocrine homeostasis [150]
 - Lateral hypothalamus [27,28] Orexin – Feeding behavior, Temperature regulation, Nociception, Reward [151]
Thalamus:
 - Thalamic reticular nuclei [24] GABA – Modulation of thalamic nuclei [152]
 - Intralaminar thalamic nuclei [24] (centromedian, parafascicular, centrolateral) Glutamate – Nociception, Motor [153]
Basal forebrain:
 - Nucleus accumbens, nucleus basalis, diagonal band of Broca [24,27] Acetylcholine – Memory, Attention [154]
a

“Ascending” refers to the fact that several pathways of this system involve ascending fibers from the brainstem, hypothalamus, thalamus and basal forebrain to the cortex.

b

Note that we only list brain regions that are thought to directly increase arousal (e.g. level of wakefulness, responsiveness to stimuli). In addition, arousal could also be increased by inhibiting sleep promoting brainstem (e.g lateral pontine tegmentum) and hypothalamic (ventrolateral preoptic nucleus) nuclei.

For a review of sleep promoting regions and their involvement in sleep state switching see [28].