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Cited by 4,307Neuroscience of respiration and sleepSleep and Wakefulness ResearchNeural dynamics and brain function

Brain stem reticular formation and activation of the EEG

Moruzzi, G., Magoun, H.W.·1949·Electroencephalography and Clinical Neurophysiology
DOI 10.1016/0013-4694(49)90219-9
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Abstract

1. Stimulation of the reticular formation of the brain stem evokes changes in the EEG, consisting of abolition of synchronized discharge and introduction of low voltage fast activity in its place, which are not mediated by any of the known ascending or descending paths that traverse the brain stem. The alteration is a generalized one but is most pronounced in the ipsilateral hemisphere and, sometimes, in its anterior part. 2. This response can elicited by stimulating the medical bulbar reticular formation, pontile and midbrain tegmentum, and dorsal hypothalamus and subthalamus. The bulbar effect is due to ascending impulses relayed through these more cephalic structures. The excitable substrate possesses a low threshold and responds best to high frequencies of stimulation. 3. Some background synchrony of electrocortical activity is requisite for manifestation of the response. In the "encephale isolé", reticular stimulation has no additional effect upon the fully activated EEG. With synchrony, in spontaneous drowsiness or light chloralosane anesthesia, the effect of reticular stimulation is strikingly like Berger's alpha wave blockade, or any arousal reaction. In full chloralosane anesthesia, high voltage slow waves are blocked but no increase in lower amplitude, fast activity occurs. With barbiturate anesthesia, the reticular response is difficult to elicit or is abolished. 4. In the chloralosane preparation, the secondary cortical response evoked by a sensory volley is generally unaffected by reticular stimulation. Consequent sensory after-discharge is abolished, however, as is pyramidal tract discharge and jerky movements referable to it. Outside the sensory receiving area, secondary responses themselves may be reduced or prevented. 5. The convulsive spikes produced by local strychnine and those of a fit following supramaximal cortical excitation, are not decreased by stimulating the reticular formation. 6. The cortical recruiting response induced by low frequency stimulation of the diffuse thalamic projection system is reduced or abolished by reticular stimulation. 7. There is some indication that the cortical effect of reticular stimulation may be mediated by this diffuse thalamic projection system, for synchronized activity within it is similarly prevented by reticular excitation, and direct high frequency stimulation of this system, within the thalamus, reproduces the reticular response. It is possible, however, that other mechanisms may be involved in its mediation. 8. The reticular response and the arousal reaction to natural stimuli have been compared in the "encéphale isolé", in which EEG synchrony was present during spontaneous relaxation or was produced by recruiting mechanisms, and the two appear identical. 9. The possibility that the cortical arousal reaction to natural stimuli is mediated by collaterals of afferent pathways to the brain stem reticular formation, and thence through the ascending reticular activating system, rather than by intra-cortical spread following the arrival of afferent impulses at the sensory receiving areas of the cortex, is under investigation. 10. The possibility is considered that a background of maintained activity within this ascending brain stem activating system may account for wakefulness, while reduction of its activity either naturally, by barbiturates, or by experimental injury and disease, may respectively precipitate normal sleep, contribute to anesthesia or produce pathological somnolence.

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  • Lesions in the reticular formation of the brainstem can produce unconsciousness and coma, and stimulating the reticular formation can arouse a comatose animal and activate the thalamocortical system.

    “It has been known for a long time that lesions in the reticular formation of the brainstem can produce unconsciousness and coma. Conversely, stimulating the reticular formation can arouse a comatose animal and activate the thalamocortical system, making it ready to respond to stimuli [43].”

    From An information integration theory of consciousness (2004) · cites this paper as [43]

  • In all vertebrates, the reticular formation signals widespread activation of the cerebrum and thus is required for alertness, awareness, attention, and consciousness.

    “In all vertebrates, the reticular formation signals widespread activation of the cerebrum and thus is required for alertness, awareness, attention, and consciousness”

    From The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago (2013) · cites this paper as Moruzzi and Magoun, 1949

  • An incremental worsening in attention to a task, as reflected by slow-frequency variability in RT (SFAUS), may be linked to a deficit in brain arousal levels, related to the functioning of sub-cortical structures, the anterior cingulate and neurotransmitter dysfunction.

    “An incremental worsening in attention to a task, as reflected by slow-frequency variability in RT (SFAUS), may be linked to a deficit in brain arousal levels, related to the functioning of sub-cortical structures (locus coeruleus, pulvinar, the basal forebrain, thalamus, brain stem reticular formation), the anterior cingulate and neurotransmitter dysfunction (noradrenergic, cholinergic and seroton”

    From Dissociation in performance of children with ADHD and high-functioning autism on a task of sustained attention (2007) · cites this paper as Moruzzi & Magoun, 1949

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Authors
Moruzzi, G., & Magoun, H. W.
Affiliations
Northwestern University (US)
Venue
Electroencephalography and Clinical Neurophysiology
Publisher
Elsevier BV
Published
1949-01
Volume
1
Issue
1-4
Pages
455-473
ISSN
0013-4694 (ISSN-L)
DOI
10.1016/0013-4694(49)90219-9
OpenAlex
W2034450065
Cited by
4,307
References
36
Citations by year
2026: 32 · 2025: 63 · 2024: 57 · 2023: 73 · 2022: 69 · 2021: 100 · 2020: 72 · 2019: 87 · 2018: 88 · 2017: 75 · 2016: 80 · 2015: 105 · 2014: 78 · 2013: 98 · 2012: 97
FWCI
25.20
Type
journal article
Language
en
Open access
closed
Licence
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
Locations
  • Electroencephalography and Clinical Neurophysiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Neuroscience › Endocrine and Autonomic Systems › Neuroscience of respiration and sleep
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Sleep and Wakefulness Research
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Neural dynamics and brain function
Keywords
brainstem reticular formation, EEG activation, arousal, cortical recruitment, chloralose anesthesia, barbiturate anesthesia, brainstem stimulation, cortical excitation, dorsal hypothalamus
MeSH terms
Afferent Pathways, Brain Stem, Electroencephalography, Evoked Potentials, Reticular Formation, Sleep, Tegmentum Mesencephali, Thalamus, Wakefulness

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