The vestibular system

The library took away The Second Brain and there’s a long wait to get it back, so we’ll be putting digestive issues aside for a moment  and talking more about sensory stuff.  While I have a variety of issues that are in retrospect sensory, the driving complaint that drove me to seek treatment was misophonia.  You know how nails on a chalkboard or a crying baby creates a kind of aural pain you can’t block out?  Misophonia is having that reaction to sounds normally considered safe.   http://misophonia-meerkat.tumblr.com/ is full of people are driven to thoughts of self harm or even suicide by very common sounds, like breathing, low bass, and typing.   Luckily, I’m not nearly that bad.  But I also find it almost impossible to concentrate when people are talking, and work in an open office.

I have a new SI therapist (who I have yet to compare to a Guantanamo Bay interrogator, which makes her much better than the last one) who says my problem lies in my vestibular system, so let’s do some recon on that.  The vestibular system has two parts: a series of canals that track rotational acceleration, and two sacs that track acceleration in a single direction.  I wrote several paragraphs explaining exactly how these work, but ultimately I don’t think I added much over wikipedia, so I’m just going to summarize.  The canals and sacs are constructed differently but operate on the same physical principle:  if you have a rigid container holding a liquid, the atoms in the solid share momentum/inertia with each other but not the atoms in the liquid.  That’s why you can spill water by moving a glass very quickly, even if it’s perfectly level the whole time.  The canals and sacs detect this somewhat differently- the canals are filled with an electrically charged fluid (endolymph) that interacts with electrically sensitive hairs when you spin, which triggers a signal to the relevant nerve.  You have three canals, each of which detects rotation in a different plane.  Do not bother reading the descriptions of which plane each covers, they do not make any sense.  Instead, read this article on the axes of rotation for airplanes.  The theory is equivalent and the pilots have much better diagrams.

The sacs have a number of stones or crystals sitting in a gel, and nervous system is triggered when the stone hits the sac wall, bending the hairs on it.   Both sacs provide information on both horizontal and verticle movement, but the uticle is more sensitive to vertical movement and the saccule more sensitive to horizontal.

Note that both of these track changes in movement, not movement itself.  In order to track speed, your brain needs to keep track of your existing state and then calculate the change indicated by the vestibular organs.  It then automagically triggers the necessary changes in posture and eye movement to keep you upright and looking at your target.  That is why you can read when shaking your head, but not when someone moves your book.

Motion sickness is caused by a disagreement between your vestibular system and your eyes about how fast you are moving, which means my trick of looking at a fixed point in the vehicle was exactly wrong.  What I need to do is look outside so my eyes track motion.

At this point, I have two questions:  what can go wrong in these systems, and how to do they relate to misophonia, which is a hearing thing, not a balance thing?