Reality Pain Attenuation

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14 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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The Neurobiology of Virtual
Reality Pain Attenuation

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Neuropharmacology

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9
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Outline


What is Virtual Reality


Introduction


Virtual Reality as a Distraction


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What is Virtual Reality


“a realistic simulation of
an environment, including
three
-
dimensional
graphics, by a computer
system using interactive
software and hardware.“

4

Introduction


Has been shown to be a powerful clinical tool
in a variety of applications.


Has been particularly effective when used to
manage acute pain with patients undergoing
invasive medical procedures.


Field of VR pain attenuation is still in its
infancy.

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VR and Pain Attenuation


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Virtual Reality as a Distraction


Distraction is an effective means
of managing pain during acute
and invasive medical procedures.


VR distracts the patients from the
unpleasantness of the procedure
and hospital setting by putting
them in a pleasant and absorbing
virtual environment.


This is done through visual,
auditory and tactile cues.


Use of VR helmets helps the
patient to focus on the virtual
environment by limiting visual
and auditory stimuli from the
outside world.


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Experiments


Earliest study looked at the effects of visual input on phantom limb
sensation(16)


Used a “virtual reality mirror box”


6 out of 10 patients reported sensation in their phantom limb after
viewing the mirror image of their uninjured hand.


Studies with burn victims (9,10,11,23) have shown that virtual
environments can produce profound nonpharmacological analgesic effects,
significantly reducing pain during physical therapy.


These effects occurred with VR therapy alone and when it was coupled
with analgesic drugs.


Other studies have shown the benefits of virtual reality for outpatient
chemotherapy for breast cancer, adolescents with cancer undergoing
lumbar puncture, children undergoing venipuncture, and children requiring
IV placement for MRI and CT scans.


Unfortunately, it is still not well understood how VR affects the perception
of pain.

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VR and the Neurobiology of Pain


Pain is an extremely important sense as it is critical
for the survival of an individual, as well as species.


Early studies have shown that pain is a subjective
phenomena that is actually only loosely related to a
specific injury or bodily insult. (1)


Today we know a great deal more about the ways
pain is transmitted and perceived, modulated by the
brain, and affected by drugs than we did in the past.

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The Neurobiology of Pain


Normally, pain is detected by nociceptors. They are located
throughout the body in the skin, muscles, and organs.


They respond to stimuli indicating any potential damage to tissue and
then relay the information toward the central nervous system via A
-
delta fiber and C fiber neurons


A
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delta fibers transmit those pain signals that are perceived as
sharp or burning.


These fibers are myelinated, with conduction speeds of up to 30m per
second, to handle such important information.


C fibers deal with dull and aching pain signals.


These fibers are not myelinated, with conduction speeds of only 0.5
-
2m
per second, due to the lower priority of such signals.

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The Neurobiology of Pain


By interrupting the body’s normal means of detecting pain, analgesia can be achieved.


Primary target of analgesic development has been the C fibers.


It is unlikely that analgesia produced by VR is due to direct effects on C fiber signaling.



Gate Control Theory (GTC) says that “nerve gates” determine the degree to which a pain sensation enters
into the awareness of an individual.



On top of GTC the existence of an intricate descending pain
-
control system that originates in the brain has
been demonstrated.


Activation of this system occurs through the fibers descending from the periaqueductal grey (PAG) area of the
midbrain.


This activation produces pronounced analgesia.


Microinjections of opioid agonists into the this system have also produced analgesia.


Electrical stimulation of the PAG has produced analgesia.


Opioid agonists, such as naloxone, have blocked such analgesia.


This system can also facilitate the transmission of pain.


Possibly explains why the experience of heightened pain is often produced by hypervigilance and emotional concerns about pain
.



The PAG also receives input from various areas of the brain, including those cortical regions involved in
attention and emotion.


This suggests that the modulation of the descending pain
-
control system might underlie the effects of emotion and
attention on the perception of pain.


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Attention, VR, and Pain


VR works by distraction


fMRI studies have shown that cortical areas
associated with attentional processes and pain
modulation are more active during distraction, while
those areas associated with pain perception are less
active.


During pain with distraction compared to pain alone, he
PAG, orbitofrontal cortex, and perigenual ACC all show
increased activation.


Areas of the pain matrix showing decreased activation
during distraction include the insular cortex, midcingulate
ACC and the thalamus.

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Attention, VR, and Pain


The ACC is divided into two sections

1. Perigenual


Functions to mediate the attentional processes and emotional reaction to pain.


Shows increased activity during distraction to pain.


Activation produces analgesia.

2. Midcingulate


Demanding cognitive tasks activate it.


Shows decreased activity during distraction to pain.



Given that the descending pain
-
modulation pathway can be activated by
stimulation of the PAG, it is hypothesized that the ACC effects structures,
such as the PAG, that modulate pain.


The VR distracts the person


activating the perigenual ACC


activating
the PAG


stimulating the descending pain
-
modulation system


producing
analgesia.


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Emotion, VR, and Pain


Emotion can also have an impact on the perception of pain.


Thought to occur via the descending pain
-
control system.


The amygdala can produce either inhibition or facilitation of pain perception by
interacting with the ACC and the PAG


There is evidence showing that negative emotions, such as fear and stress, activate a
section of the amygdala, which results in the inhibitory pain
-
control pathways being
activated.


Other evidence shows that negative emotions like anxiety and depression, result in the
facilitation of pain.


One study has shown than positive emotions can result in a decrease in pain.


This analgesia is theorized to occur due to the emotions inhibiting the portion of the
amygdala that facilitates pain.



Greater research is needed in this area though to fully understand the
mechanisms of action though.


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Future Directions


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Conclusion


Despite all the studies showing the efficacy of using
VR, we still do not know all the neurobiological
mechanisms underlying it.


Further research targeting the neurobiological
correlates of pain attenuation are needed.


This is necessary so that we might better understand the
biological and psychological factors that govern pain.


Future research could lead to the development of new
and more effective methods of using VR to treat pain.


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Sources


Gold, J., Belmont, K., & Thomas, D. (2007, August). The Neurobiology of Virtual Reality Pain Attenuation.
CyberPsychology & Behavior
,
10
(4), 536
-
544.