Lecture 21 Flashcards
What does galvanic mean?
- Constant Current
What is Galvanic Vestibular Stimulation used for?
- Detect vestibular deficiency
- Activate vestibular system artificially
What does Galvanic Vestibular Stimulation mean?
- Constant current of vestibular system using electrodes placed over mastoid process
What happens in a healthy individual when you place electrodes over the mastoid processes?
- the current messes with the vestibular system
What is located under the mastoid process?
- Cranial Nerve XIII
What does cathode stimulation do using galvanic vestibular stimulation?
- Increases firing of peripheral vestibular afferents
What does the anode do during galvanic vestibular stimulation?
- Decreases firing of peripheral vestibular afferents
What happens as a result of galvanic vestibular stimulation?
- Distinct sway towards the anode side
- More pronounced with eyes closed
- Causes roll of segments relative to each other
- Ocular torsion with eyes open
What happens when you remove the stimulus of a galvanic vestibular stimulation?
- Returns back to background discharge
What happens when you change the current of the electrical perturbations of a galvanic vestibular stimulation?
- more current: get more modulation
- creates artificial change to the vestibular firing rate
Why would you use Galvanic Vestibular Stimulation?
Test Vestibular System
- Creates temporary/distinct vestibular perturbation
- Magnitude and duration are easily controlled
- GVS results in predictable and well-documented postural response
What do you look for when testing the vestibular system using galvanic vestibular stimulation?
If working properly
- Sway toward anode side
- Ocular torsion with eyes open
If not working
- No response
When do we pay more attention to the vestibular system than the visual input?
- When the eyes are closed
What happens if the anode is on the right ear during galvanic vestibular stimulation?
- Sway to the right
What is the roll illusion of galvanic vestibular stimulation?
- Where the somatosensory system thinks the head is
How can Galvanic Vestibular Stimulation effect postural muscles?
- They will turn on when limit is reached to maintain balance
- Can affect walking, and standing
What was Assigned Reading 6 done for?
To Identify
- Role of the vestibular system for locomotion
- What do you use it for
- When it is used
- When is it important
What was the setup for Assigned Reading 6?
Plate with microswitch
- turns on galvanic current when stepped on
- Randomize if anode on left or right ear
- 3 different levels of stimulation
What was the three levels of stimulation for Assigned Reading 6?
X threshold
- 1
- 2
- 3
How was the threshold determined in Assigned Reading 6?
- Slowly increase the current until it causes movement
- results in their specific threshold
- Different for everybody
How did they assess the subjects in Assigned Reading 6?
Cameras in front of subject and over top
- Reflective markers on shoulders and head
- Track how they walk when stim on
What did the reflective markers show?
- How the stimulus affects trajectory of walking with eyes closed
In Assigned Reading 6, what was the walking pattern with no stimulation?
- “straight line”
- centre of mass shifts subtly (weaves)
In Reading Assignment 6, what was the walking pattern when level 3 stimulus was activated?
- Deviation to left (when anode on left)
- Deviation to right (when anode on right)
In Assigned Reading 6, was there any deviation with level 1 stimulus? What about level 2? What about level 3?
Level 1
- Subtle deviation
Level 2
- bigger deviation
Level 3
- slightly more than level 3
In Assigned Reading 6, what did the subtle difference between level 2 and level 3 stimulus show?
- Seems to be a threshold for how much you could drive people using GVS
In Assigned Reading 6, What happened when the trials were run with Eyes Open?
- Greatly reduced deviation
