Periaqueductal gray: Difference between revisions
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==Role in consciousness== |
==Role in consciousness== |
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If there is a [[lesion]] in the PAG, then [[consciousness]] is lost. This observation does not mean that the PAG, itself, is the center of consciousness, but rather that it is a critically needed part of it.<ref name="TSN Consciousness">[http://thesciencenetwork.org/programs/origins-symposium/panel-1-consciousness-complex-cognition-and-language Patricia Churchland (Video)] (2009), Consciousness panel of The Science Network (min. 26)</ref><ref name="kdkdk">[http://www.ingentaconnect.com/content/jbp/ce/2000/00000001/00000001/art00005 Watt D.FT] (2000), "The centrecephalon and thalamocortical integration: Neglected contributions of periaqueductal gray".</ref> |
If there is a [[lesion]] in the PAG, then [[consciousness]] is lost. This observation does not mean that the PAG, itself, is the center of consciousness, but rather that it is a critically needed part of it.<ref name="TSN Consciousness">[http://thesciencenetwork.org/programs/origins-symposium/panel-1-consciousness-complex-cognition-and-language Patricia Churchland (Video)] (2009), Consciousness panel of The Science Network (min. 26)</ref><ref name="kdkdk">[http://www.ingentaconnect.com/content/jbp/ce/2000/00000001/00000001/art00005 Watt D.FT] (2000), "The centrecephalon and thalamocortical integration: Neglected contributions of periaqueductal gray".</ref> |
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=Emotions= |
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Periaqueductal gray is involved in three different process of emotions.<ref>{{cite book|last=Jenkins|first=Dacher Keltner, Keith Oatley, Jennifer M.|title=Understanding emotions|publisher=Wiley|location=Hoboken, N.J.|isbn=9781118147436|edition=3rd ed.}}</ref> |
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==Release of opioids== |
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Periaqueductal gray assist in the release of opioids. The pain signals are inhibited before they reach the cortex and allows to escape threat before attending to bodily harm. The Periaqueductal gray helps the individual to regulate the pain.<ref>{{cite book|last=Jenkins|first=Dacher Keltner, Keith Oatley, Jennifer M.|title=Understanding emotions|publisher=Wiley|location=Hoboken, N.J.|isbn=9781118147436|edition=3rd ed.}}</ref> |
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==Negative Emotions== |
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Periaqueductal gray is activated by the images of negative emotions along with pain. According to a recent investigation, increased activation on the Periaqueductal gray is shown in response to thermal pain and viewing distressing slides.<ref>{{cite book|last=Jenkins|first=Dacher Keltner, Keith Oatley, Jennifer M.|title=Understanding emotions|publisher=Wiley|location=Hoboken, N.J.|isbn=9781118147436|edition=3rd ed.}}</ref> |
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==Caregiving System== |
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In the mammalian brain, Periaqueductal gray is a part of caregiving system. Nurturant behaviors like crouching over pups, retrival to nest, licking and nursing engage the Periaqueductal gray. Periaqueductal gray was obseved along with other networking empathy regions. Periaqueductal gray is activated to pain responses, by signs of distress and negative emotion of the caregiving tendencies.<ref>{{cite book|last=Jenkins|first=Dacher Keltner, Keith Oatley, Jennifer M.|title=Understanding emotions|publisher=Wiley|location=Hoboken, N.J.|isbn=9781118147436|edition=3rd ed.}}</ref> |
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==Additional images== |
==Additional images== |
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Revision as of 17:40, 8 August 2013
| Periaqueductal gray | |
|---|---|
 Section through superior colliculus showing path of oculomotor nerve. Periaqueductal gray is the gray area just peripheral to the cerebral aqueduct.) | |
 Coronal section through mid-brain. 1. Corpora quadrigemina. 2. Cerebral aqueduct. 3. Central gray stratum. 4. Interpeduncular space. 5. Sulcus lateralis. 6. Substantia nigra. 7. Red nucleus of tegmentum. 8. Oculomotor nerve, with 8’, its nucleus of origin. a. Lemniscus (in blue) with a’ the medial lemniscus and a" the lateral lemniscus. b. Medial longitudinal fasciculus. c. Raphé. d. Temporopontine fibers. e. Portion of medial lemniscus, which runs to the lentiform nucleus and insula. f. Cerebrospinal fibers. g. Frontopontine fibers. | |
| Details | |
| Identifiers | |
| Latin | Subtstantia grisea centralis |
| MeSH | D010487 |
| NeuroNames | 1584 |
| NeuroLex ID | birnlex_973 |
| TA98 | A14.1.06.321 |
| TA2 | 5909 |
| FMA | 83134 |
| Anatomical terms of neuroanatomy | |
Periaqueductal gray (PAG; also called the "central gray") is the gray matter located around the cerebral aqueduct within the tegmentum of the midbrain. It plays a role in the descending modulation of pain and in defensive behaviour. The ascending pain and temperature fibers of the spinothalamic tract also send information to the PAG via the spinomesencephalic tract (so-named because the fibers originate in the spine and terminate in the PAG, in the mesencephalon or midbrain).
Role in analgesia
Stimulation of the periaqueductal gray matter of the midbrain activates enkephalin-releasing neurons that project to the raphe nuclei in the brainstem. 5-HT (serotonin) released from the raphe nuclei descends to the dorsal horn of the spinal cord where it forms excitatory connections with the "inhibitory interneurons" located in Laminae II (aka the substantia gelatinosa). When activated, these interneurons release either enkephalin or dynorphin (endogenous opioid neurotransmitters), which bind to mu opioid receptors on the axons of incoming C and A-delta fibers carrying pain signals from nociceptors activated in the periphery. The activation of the mu-opioid receptor inhibits the release of substance P from these incoming first-order neurons and, in turn, inhibits the activation of the second-order neuron that is responsible for transmitting the pain signal up the spinothalamic tract to the ventroposteriolateral nucleus (VPL) of the thalamus. The nociceptive signal was inhibited before it was able to reach the cortical areas that interpret the signal as "pain" (such as the anterior cingulate). This is sometimes referred to as the Gate control theory of pain and is supported by the fact that electrical stimulation of the PAG results in immediate and profound analgesia.[1]
Three known kinds of opioid receptors have been identified: mu (μ), kappa (κ) and delta (δ). Synthetic opioid and opioid-derivative drugs activate these receptors (possibly by acting on the PAG directly, where these receptors are densely expressed) to produce analgesia. These drugs include heroin, morphine, pethidine, hydrocodone, oxycodone, and similar pain-reducing compounds.
Role in defensive behavior
Stimulation of the dorsal and lateral aspects of the PAG (in the rat) can provoke defensive responses characterised by freezing immobility, running, jumping, tachycardia, and increases in blood pressure and muscle tonus. In contrast, stimulation of the caudal ventrolateral PAG can result in an immobile, relaxed posture known as quiescence, whereas its inhibition leads to increased locomotor activity.
Lesions of the caudal ventrolateral PAG can greatly reduce conditioned freezing, whereas lesions of the dorsal aspect can reduce innate defensive behavior, virtually "taming" the animal.
Role in reproductive behavior
Neurons of the PAG are excited by endorphins and by opiate analgesics. It also plays a role in female copulatory behavior (see Lordosis behavior) via a pathway from the ventromedial nucleus of the hypothalamus.
Role in maternal behavior
The PAG may be specifically involved in human maternal behavior. The PAG contains a high density of vasopressin and oxytocin receptors, and it has direct connections with the orbitofrontal cortex, which might mediate the role of the PAG in maternal love. The lateral orbitofrontal cortex is activated by pleasant visual, tactile, and olfactory stimuli. Its response depends on pleasantness rather than on intensity of stimulation. Here, its activity is likely to reflect one aspect of the pleasant emotions associated with motherly love.[2]
Role in consciousness
If there is a lesion in the PAG, then consciousness is lost. This observation does not mean that the PAG, itself, is the center of consciousness, but rather that it is a critically needed part of it.[3][4]
Emotions
Periaqueductal gray is involved in three different process of emotions.[5]
Release of opioids
Periaqueductal gray assist in the release of opioids. The pain signals are inhibited before they reach the cortex and allows to escape threat before attending to bodily harm. The Periaqueductal gray helps the individual to regulate the pain.[6]
Negative Emotions
Periaqueductal gray is activated by the images of negative emotions along with pain. According to a recent investigation, increased activation on the Periaqueductal gray is shown in response to thermal pain and viewing distressing slides.[7]
Caregiving System
In the mammalian brain, Periaqueductal gray is a part of caregiving system. Nurturant behaviors like crouching over pups, retrival to nest, licking and nursing engage the Periaqueductal gray. Periaqueductal gray was obseved along with other networking empathy regions. Periaqueductal gray is activated to pain responses, by signs of distress and negative emotion of the caregiving tendencies.[8]
Additional images
-
Schematic representation of the chief ganglionic categories (I to V). -
Transverse section of mid-brain at level of inferior colliculi. -
Transverse section of mid-brain at level of superior colliculi. -
MRI section of human mid-brain showing periaqueductal gray
See also
References
- ^ Basbaum AI, Fields HL (1978). "Endogenous pain control mechanisms: review and hypothesis". Ann. Neurol. 4 (5): 451–62. doi:10.1002/ana.410040511. PMID 216303.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Andreas Bartels and Semir Zeki (2004). "The neural correlates of maternal and romantic love" (PDF). NeuroImage. 21 (3): 1155–1166. doi:10.1016/j.neuroimage.2003.11.003. PMID 15006682.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Patricia Churchland (Video) (2009), Consciousness panel of The Science Network (min. 26)
- ^ Watt D.FT (2000), "The centrecephalon and thalamocortical integration: Neglected contributions of periaqueductal gray".
- ^ Jenkins, Dacher Keltner, Keith Oatley, Jennifer M. Understanding emotions (3rd ed. ed.). Hoboken, N.J.: Wiley. ISBN 9781118147436.
{{cite book}}:|edition=has extra text (help)CS1 maint: multiple names: authors list (link) - ^ Jenkins, Dacher Keltner, Keith Oatley, Jennifer M. Understanding emotions (3rd ed. ed.). Hoboken, N.J.: Wiley. ISBN 9781118147436.
{{cite book}}:|edition=has extra text (help)CS1 maint: multiple names: authors list (link) - ^ Jenkins, Dacher Keltner, Keith Oatley, Jennifer M. Understanding emotions (3rd ed. ed.). Hoboken, N.J.: Wiley. ISBN 9781118147436.
{{cite book}}:|edition=has extra text (help)CS1 maint: multiple names: authors list (link) - ^ Jenkins, Dacher Keltner, Keith Oatley, Jennifer M. Understanding emotions (3rd ed. ed.). Hoboken, N.J.: Wiley. ISBN 9781118147436.
{{cite book}}:|edition=has extra text (help)CS1 maint: multiple names: authors list (link)