Caloric Stimulation of the Vestibular System

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Caloric Stimulation of the Vestibular System
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What is caloric stimulation?

• A reflex that occurs when cold water or air is
  put into the human ear.
• The cold water/air begins to draw heat away from
  the inner ear and creates a convection current in
  the semi-circular canals (because of the
  temperature differential)
• The result is that the brain misinterprets this
  as a signal that you are spinning around and you
  begin to feel dizzy
• You then start to experience optokinetic
  nystagmus as your eyes react to the brains
  interpretation of the spinning

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Neurology Caloric Stimulation

• Caloric stimulation is a commonly used
  neurological technique.
• It is most useful for determining if there is
  damage to any of the ocular muscles or one of the
  cranial nerves.

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Why might caloric stimulation affect people?

• Lateral Line System in Fish
• Used for orienting reflex to find prey or hide
  from predators
• Directly related to fishs body image and
  position in space

• These are the phylogenetic origins of human
  inner-ear hair cells
• So it makes sense that our own vestibular system
  might be strongly connected to our perception of
  body image and position in space

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Human Studies

• fMRI studies show strong activation of the
  parietal lobe with caloric stimulation

So whats the big deal?
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Strange effects of caloric stimulation

• Hemi-neglect
• Anosognosia Denial of paralysis
• Phantom Limb Pain
• Phantom Hand Mapping