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PGO waves

pgo waves, pgo waves dreaming
Ponto-geniculo-occipital waves or PGO waves are phasic field potentials These waves can be recorded from the pons, the lateral geniculate nucleus LGN, and the occipital cortex regions of the brain, where these waveforms originate The waves begin as electrical pulses from the pons, then move to the lateral geniculate nucleus residing in the thalamus, and then finally end up in the primary visual cortex of the occipital lobe The appearances of these waves are most prominent in the period right before rapid eye movement sleep or REM sleep, and are theorized to be intricately involved with eye movement of both wake and sleep cycles in many different animals


  • 1 Discovery
  • 2 Detection
  • 3 Mechanism for generation and propagation
    • 31 Executive neurons
      • 311 Triggering neurons
      • 312 Transfer neurons
    • 32 Modulatory neurons
      • 321 Aminergic neurons
      • 322 Cholinergic neurons
      • 323 Nitroxergic neurons
      • 324 GABA-ergic neurons
      • 325 Vestibular nuclei
      • 326 Amygdala
      • 327 Suprachiasmatic nuclei
      • 328 Auditory stimulation
      • 329 Basal ganglia
  • 4 REM sleep
  • 5 Future research
  • 6 Additional images
  • 7 See also
  • 8 References
  • 9 Further reading
  • 10 External links


The discovery of PGO waves goes back to 1959, when three French scientists released their scientific article of their study of these waves in animal test subjects1 Although at this time, they did not have a specific name for this neurological phenomenon

It was not until the published work of two American scientists that these waves became known as PGO waves2 Their research focused on the propagation of these waves in cats, noticing that these field potentials started in the pons, propagating down to the lateral geniculate nucleus and the occipital lobe

Other studies with these waves have been done on rats as well Scientists tried to discern whether the rats had PGO waves, but learned that they are present only in the pons, and wave propagation does not excite any neurons in the lateral geniculate nucleus3 As a result of this study, PGO waves are known as P waves in rodents

PGO waves have been studied mostly through cat and rodent animal models Despite the focus of the research, PGO waves have been found to exist in other mammalian species including humans and nonhuman primates, such as the macaque and baboon4


In the original experiments, PGO waves or P waves in rodent models are found by placing electrodes inside the brain, next to either the pons, lateral geniculate nuclei, or occipital lobe Along with electroencephalography EEG recording techniques, scientists are also able to show the correlation between other brain waves associated with REM sleep and PGO waves

Although scientists know they exist, PGO waves have not been detected in healthy humans due to the ethical concerns about accessing these areas where the readings need to be taken from However, advances in deep brain stimulation has made it possible to put electrodes inside the brains of humans with different pathologies and make EEG recordings of different nuclei Due to the similarities with the animal models, we can infer that PGO waves are happening at the same frequency in human EEGs56 Thus, scientists can infer that PGO waves exist in humans

Mechanism for generation and propagationedit

The neurophysiological studies on PGO waves conclude that the generation of these waves reside in a collection of neurons located in the pons, regardless of species research is done on7 From this point, the neurons branch out in a network that leads the phasic electrical signal toward the lateral geniculate nucleus and the occipital lobe

Within this network, there are two types of neuronal groups: executive neurons and modulatory neurons

Executive neuronsedit

These neurons are the ones that help to generate and propagate the PGO waves throughout the brain One research paper further breaks down this "class" of neurons into two subsets: triggering neurons and transfer neurons4 All of these neurons are located in the peribrachial area, which is a group of neurons surrounding the superior cerebellar penduncle

Triggering neuronsedit

These neurons are located in the caudolateral region of the peribrachial area These neurons actively fire during non-REM NREM sleep The most recorded activity of the neurons is during the N3 stage of NREM, also known as the slow-wave sleep cycle These same neurons are also active during REM sleep, but at a greatly reduced amplitude than NREM sleep7

Transfer neuronsedit

The neuronal cells that allow for the transfer of PGO waves from the pons to the other parts of the brain reside on the rostral portion of the peribrachial area This grouping of cells fire in precisely two modes The first mode is burst firing through low-threshold Calcium Ca2+ ion channels The other mode is a repetitive tonic firing through Sodium Na+ dependent ion channels8

During the times when triggering neurons are firing, these cells receive those signals and begin increasing their firing This, in turn, allows the wave to go out to the other portions of the brain

Modulatory neuronsedit

As the executive neurons are firing, the spread of the wave is controlled by both excitatory and inhibitory inputs These inputs come from the modulatory neurons, which help to regulate and control the amplitude and frequency of the wave The following types of cells play a huge part in this control process

Aminergic neuronsedit

Aminergic neurons are neurons that use monoamines as a neurotransmitter This class of neurotransmitters is what keeps PGO wave amplitudes at very low levels during periods of a mammal being awake The three specific aminergic neurotransmitters are serotonin, dopamine and norepinephrine9

Cholinergic neuronsedit

Cholinergic neurons are neurons that use acetylcholine as a neurotransmitter Through different studies, these types of neurons have been proven to promote PGO wave generation, thus being an excitatory neuromodulator for triggering neurons10

Nitroxergic neuronsedit

Nitroxergic neurons use nitric oxide NO as a neurotransmitter In theory, the increase of nitric oxide is seen as an excitatory neuromodulator in PGO wave generation4 This stems from animal testing that has shown increases in PGO waves as nitric oxide levels were increased in the pons11

GABA-ergic neuronsedit

GABA-ergic neurons use gamma-aminobutyric acid GABA as a neurotransmitter These neurons are theorized to be inhibitory to aminergic neurons, and thus inhibitory to PGO wave propagation4

Vestibular nucleiedit

The neurons within the vestibular nuclei region of the brain have been shown to provide excitatory bouts of PGO wave generation when stimulated12 The tests showed that, while the vestibular nuclei aided in creating PGO waves, the excitation of this area of the brain was in no way needed for PGO wave formation


The neurons within the amygdala region of the brain have also been shown to provide excitatory bouts of PGO wave generation when electrically stimulated13

Suprachiasmatic nucleiedit

The neurons within the suprachiasmatic nuclei region of the brain help to regulate REM sleep14 The REM sleep cycle length causes the frequency of PGO waves to be phase lockedclarification needed

Auditory stimulationedit

The use of auditory stimulation has been shown to increase PGO waves during waking and sleeping cycles with neurons associated with transfers of auditory information15 Even while the subject is awake and in total darkness, the amplitude of PGO waves increases by auditory stimulation Another study also found that auditory stimulation increased the amplitude of PGO waves in slow-wave sleep and REM sleep and did not reduce the amplitude of the waves with repeated auditory stimulation16 From this research, scientists can theorize that PGO wave generation from auditory stimulation contains a positive-feedback mechanism that can be excited by evoked PGO waves4

Basal gangliaedit

The basal ganglia are a group of nuclei in the brains of vertebrates, situated at the base of the forebrain and strongly connected with the cerebral cortex, thalamus and pons The basal ganglia are associated with a variety of functions, including arousal, motor control and learning The main components of the basal ganglia are the striatum, pallidum, substantia nigra, and subthalamic nucleus or subthalamus This latter, glutamatergic nucleus is reciprocally connected with the PGO-transferring nuclei of the pons In humans, subthalamic PGO-like waves, that resemble the PGO waves typically recorded in cats, can be recorded during pre-REM and REM sleep17 This suggests that the subthalamus may play an active role in an ascending activating network implicated in the rostral transmission of PGO waves during REM sleep in humans17

REM sleepedit

PGO waves are an integral part of rapid eye movement REM sleep As stated earlier, the density of the PGO waves coincides with the amount of eye movement measured in REM sleep This has led some researchers to further theorize about the usefulness of PGO waves for dreaming

One key use of REM sleep is for the brain to process and store information from the previous day In a sense, the brain is learning by establishing new neuronal connections for things that have been learned Neurophysiological studies have indicated a relationship between increased P-wave density during post-training REM sleep and learning performance1819 Basically, the abundance of PGO waves translates into longer periods of REM sleep, which thereby allows the brain to have longer periods where neuronal connections are formed

The importance of PGO waves during REM sleep also aids the idea of PGO waves as a signal that a person is dreaming20 Since dreaming occurs during REM sleep, the PGO waves are theorized to be the signals that make the brain start to recount the experiences from the previous day This, in turn, allows us to "see" our dreams since our visual sense is quickly going through the information it has stored

For more information of the importance of PGO waves during REM sleep, please refer to Activation synthesis theory

Future researchedit

The next big area to research regarding this topic is to understand what processes PGO waves are beneficial for in both states of sleep as well as consciousness Although PGO waves are noticeably present during NREM sleep, some scientistswho believe they are also present during waking cycles There is a possibility that PGO waves are essential for image correction of the eyes, since PGO waves are signals on a pathway that allow the motor cortex of the brain to interface with the vision system

The other future interests in research of this topic are what PGO waves are precisely doing for us while we are dreaming Some scientistswho theorize that PGO waves are essential for stabilizing the images that we have in our dreams This theory comes from the eye movements that coincide with the readings from electrodes picking up PGO waves

Also, scientists seek to discover how the presence of these signals fits in with the overall dreaming process Research in PGO waves is of broad importance to neurophysiology because it involves the coordination of entire regions of the brain working together—coming from many different systems—to create our dreams, memories, and other experiences that we have

Another area of potential research interest involves PGO waves during lucid dreaming, active imagination and hallucination21

Additional imagesedit

Human brain photos
Anteroinferior view of the medulla oblongata and pons 
Hind- and mid-brains; postero-lateral view Lateral geniculate body visible near top 
Lobes of the human brain the occipital lobe is shown in red 

See alsoedit

  • Dream
  • Electroencephalography EEG
  • Sleep
  • REM sleep
  • NREM sleep
  • Pons
  • Lateral geniculate nucleus
  • Occipital Lobe
  • Subthalamic nucleus
  • Alpha wave
  • Beta wave
  • Delta wave
  • Gamma wave
  • Mu wave
  • Theta wave


  1. ^ Jouvet, M, Michel, F, and Courjon, J 1959 L'activite electrique du rhinencephale au cours dusommeil chez le chat CR Soc Biol 153:101–105
  2. ^ Brooks, DC, and Bizzi, E 1963 Brain stem electrical activity during deep sleep Arch Ital Biol101:648–665
  3. ^ Stern, WC, Forbes, WB, and Morgane, PJ 1974 Absence of ponto-geniculo-occipital PGO spikes in rats Physiol Behav 12:293–295
  4. ^ a b c d e Datta S 1997 Cellular basis of pontine ponto-geniculo-occipital wave generation and modulation Cellular and Molecular Neurobiology 17:341–65
  5. ^ Fernández-Mendoza J, Lozano B, Seijo F, Fernández-González F, Vela-Bueno A 2006 Subthalamic nucleus activity during human REM sleep: the PGO-like waves J Sleep Res 2006;15:243
  6. ^ Lim AS, Lozano AM, Moro E, Hamani C, Hutchison WD, et al 2007b Characterization of REM-sleep associated ponto-geniculo-occipital waves in the human pons Sleep 30:823–7
  7. ^ a b Datta, S, and Hobson, JA 1994 Neuronal activity in the caudo-lateral peribrachial pons:Relationship to PGO waves and rapid eye movements J Neurophysiol 71:95–109
  8. ^ Williams, JA, and Reiner, PB 1993 Noradrenaline hyperpolarizes identified rat mesopontine cholinergic neurons in vitro J Neurosci 13:3878–3883
  9. ^ Brooks, D C; Gershon, M D 1977-01-01 "Amine repletion in the reserpinized cat: effect upon PGO waves and REM sleep" Electroencephalography and Clinical Neurophysiology 42 1: 35–47 doi:101016/0013-46947790149-3 ISSN 0013-4694 PMID 64348 
  10. ^ Steriade, M, Datta, S, Pare, D, Oakson, G, and Currodossi, R 1990a Neuronal activities in brain-stem cholinergic nuclei related to tonic activation processes in thalamortical systems J Heurosci 10:2541–2559
  11. ^ Leonard, TO, and Lydic, R 1995 Nitric oxide synthase inhibition decreases pontine acetylcholinerelease NeuroReport 6:1525–1529
  12. ^ Morrison, AR, and Pompeiano, O 1966 Vestibular influences during sleep IV Functional relations between the vestibular nsleep Arch Ital Biol 104:425–458
  13. ^ Calvo, JM, Badillo, S, Morales-Ramirez, M, and Palacios-Salas, P 1987 The role of temporal lobe amygdala in ponto-geniculo-occipital activity and sleep organization in cats Brain Res 403:22–30
  14. ^ Siegel JM 2005 Clues to the functions of mammalian sleep Nature 437:1264–71
  15. ^ Callaway CW, Lydic R, Baghdoyan HA, Hobson JA 1987 Pontogeniculoocipital Waves – Spontaneous Visual-System ACtivity During Rapid Eye-Movement Sleep Cellular and Molecular Neurobiology 7:105–49
  16. ^ Bowker, RM, and Morrison, AR 1977 The PGO spikes: An indicator of hyperalertness In Sleep Research, WP Koella and P Levin, Eds, Karger, Basel, pp 23–77
  17. ^ a b Fernández-Mendoza J, Lozano B, Seijo F, Santamarta-Liébana E, Ramos-Platón MJ, Vela-Bueno A, Fernández-González F 2009 Evidence of subthalamic pgo-like waves during rem sleep in humans: a deep brain polysomnographic study SLEEP 329:1117–26
  18. ^ Datta, S, 2006 Activation of phasic pontine-wave generator: a mechanism for sleep-dependent memory processing Sleep Biol Rhythms 4, 16–26
  19. ^ Datta, S, Saha, S, Prutzman, SL, Mullins, OJ, Mavanji, V, 2005 Pontine-wave generator activation-dependent memory processing of avoidance learning involves the dorsal hippocampus in the rat J Neurosci Res 80, 727–737 Sleep Biol Rhythms 4, 44–54
  20. ^ Hobson JA, Pace-Schott EF, Stickgold R 2000 Dreaming and the brain: Toward a cognitive neuroscience of conscious states Behavioral and Brain Sciences 23:793–+
  21. ^ Gott, JA, Liley, DTJ, Hobson, JA, 2017 Towards a Functional Understanding of PGO Waves Front Hum Neurosci 11:89 doi: 103389/fnhum201700089

Further readingedit

External linksedit

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