Lecture Notes: The Vestibular System and Gaze Control
I. Introduction
- The vestibular system is a sensory system that contributes to our sense of balance and gaze control.
- Unlike senses like sight and hearing, the vestibular system is not as readily apparent and was only discovered in the late 19th century.
- This is because the vestibular system works unconsciously in the background to keep our balance and stabilize our gaze.
II. Functions of the Vestibular System
- Maintains balance: The vestibular system allows us to maintain balance during static activities like standing still and dynamic activities like tightrope walking.
- Stabilizes gaze: The vestibular system ensures our gaze (where we’re looking) remains steady even when our head moves. This is crucial for maintaining a clear visual world.
III. Example: Cyclist Maintaining Gaze
The lecture uses a cyclist as an example. Even though the cyclist’s body and bike are tilted while banking around a curve, the vestibular system keeps the head upright (perpendicular to the ground) to maintain a level horizon in the visual field. This is an unconscious reflex that keeps our vision stable.
IV. Consequences of Vestibular Dysfunction
- When the vestibular system malfunctions, we become acutely aware of its importance.
- Symptoms can include:
- Disbalance or feeling like the room is spinning
- Nausea and vomiting
- These symptoms can be very disturbing.
V. Upcoming Topic: Stimulus for the Vestibular System
The next part of the lecture will discuss the stimulus that activates the vestibular system.
Stimulus for the Vestibular System Vestibulloocular reflex (VOR) Gaze Control
Resources
https://www.youtube.com/watch?v=ryGMI3SpxCE https://www.youtube.com/watch?v=pEfCgraemWI
Additional Resources
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This video is a very clear and accurate description of the anatomy and function of the vestibular apparatus: https://youtu.be/dSHnGO9qGsE
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A demonstration of the VOR, which as this video shows occurs in every orientation not just the horizontal orientation that we have concentrated on. Note that the demonstrator uses the word “focus” where he should have said “fixate”: https://youtu.be/j_R0LcPnZ_w
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The importance of gaze control is dramatically and disturbingly revealed by individuals with opsoclonus in which the eyes move constantly and maintaining gaze is not possible. Opsoclonus is typically a “paraneoplastic” disease which means that a tumor secretes a factor or elicits an immune reaction that in turn affects neural function. Because of this, treatment is often aimed at the tumor or immune system with the idea that if you can prevent the factor from being made, the symptoms caused by the factor will resolve. It is often found in children suffering from neuroblastoma: https://youtu.be/YtJZZIouLHg. But can also occur in adults: https://youtu.be/zX4j0IsFbAk
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Nystagmus: This video is by a young woman with congenital nystagmus and beautifully describes her experience and suggestions for others. She accurately says that because she was born with nystagmus, she can see because her brain compensates for the movement (essentially her brain anticipates the eye movements and predicts the gaze shifts). Nonetheless, as is made clear, the compensation does not make vision easy, particularly with reading small print. As she also makes clear, the problem is with eye movements and not with vision - so glasses don’t help. But this is not true for people with acquired nystagmus who will simply cannot see a steady image, at least initially. One of the most useful parts of this presentation is the perceived character implications of her “shifty-eyed” appearance: https://youtu.be/x6gG66bT5Ds
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Here is a quick and informative video on vertigo: https://youtu.be/eeCn7Pj4nZ4. Thanks to your classmate Laura Jones for sharing!
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This video shows an animation of what happens in BPPV Vertigo: https://youtu.be/Xx5dUvtUGbE