If you go to the various web sites on vestibular problems---at most of the "Balance Centers" of excellence---(Northwestern Univ/Univ of Penn/John Hopkins/UCLA....etc)you run across---a discussion on a somatic sense called:
"Proprioception"
(somatic senses are nervous system functions that collect sensory information from the body but are not one of the special senses of sight, hearing, taste, touch, or smell)
Typically, three somatic senses are described; pain, thermoreceptivity, and mechanoreceptivity.
The latter of which includes "tactile" and "position" sense.
Most of these Balance Centers agree that there are THREE inputs to the "Brain's" balance center----and under normal circumstances they provide that information as follows:
--Vision 40%
--Vestibular 30%
--Proprioception 30%
The discussions center on what happens when the vestibular signal goes "Nutso" because of an inner ear problem, BPPV, Lab, VN, etc.....
While most people have a fairly good grasp on the first two(vision & vestibular) that last one(Proprioception)---is kind of elusive.
As you can see from the short(:-} description below---and if you think about it----when the vestibular system gets "hosed up" ---among other things---it screws up---the brain's ability to keep aware of equilibrium and any changes to it---and that throws a "heavy load" on the Proprioception System---actually throws it off-stride---which in turn----causes a lot of the problems(we post about) with the bodies "posture and movement and control" of the coordinated action of more than 650 muscles
---This is also the system that develops the "Stored Movement Templates"(i.e., long term memory) I talked about in another post---it is immanently involved in developing them---through repetitive movements(i.e, practice makes perfect).
Since the slightest movement or even the intention to move initiates widespread activity in muscles throughout the body(through the Proprioception System) and since every movement has to be correct for force, speed and position---any problems can cause a lot of problems through out the body, neck, eye, stiff/strained muscles---so it is worth(I think) knowing how this "Proprioception System" which provides 30% works/influences our problem(s).
....."BASIC PRINCIPLES
Proprioception is now generally classified as one of the somatic senses — nervous system functions that collect sensory information from the body but are not one of the special senses of sight, hearing, taste, touch, or smell. Typically, three somatic senses are described: pain, thermoreceptivity, and mechanoreceptivity, the latter of which includes tactile and position sense.
Proprioception relates primarily to the position sense and encompasses two aspects of it: static and dynamic. Static sense provides the brain with feedback about the orientation of one body part to another. It is this static sense that allows us, for instance, to reach behind our backs and clasp our hands together or to touch our index finger to our nose while keeping our eyes closed. The dynamic sense gives the brain feedback about the rate and direction of the body’s movement. We see this sense in action when we slip but the brain automatically rights us without our falling.
Thus, proprioception is actually a system of neuromuscular processes. The proprioceptive system involves (1) incoming (afferent) signals, (2) outgoing (efferent) signals, and (3) interactions between many parts of the brain. Proprioceptive receptors in the skeletal muscles (spindle cells) and on the surfaces of tendons (Golgi tendon apparatus) provide constant feedback on the positions of body segments and on the actions of muscles. Awareness of limb position and movement is also gained through the stimulation of receptors in the joints.
The brain keeps aware of equilibrium changes through the inner ear mechanisms (vestibular system), which enable the perception of gravity. The information furnished by the vestibular system is also essential for coordinating the position of the head and the movement of the eyes. There are two sets of end organs in the inner ear, or labyrinth: the semicircular canals, which respond to rotational movements (angular acceleration); and the utricle and saccule within the vestibule, which respond to changes in the position of the head with respect to gravity (linear acceleration). Functionally these organs are closely related to the cerebellum and to the reflex centers of the spinal cord and brain stem that govern the movements of the eyes, neck, and limbs.
Posture and movement are made possible by the coordinated action of more than 650 muscles. The slightest movement or even the intention to move initiates widespread activity in muscles throughout the body, and every movement has to be correct for force, speed, and position. These aspects of movement are governed by the proprioceptive system.".......
Lot going on---with balance---when working---it more or less is in "AUTO"---but when something goes wrong---auto is out the window---and the brain's equlibrum center is demanding an almost constant processing power---for something---that it(brain) had relegated to auto(i.e., had learned and committed to long term memory)----.....
Want to see it in action:
First: Put four "X's" in two rowes of ten (side by side--twenty total) with each group of four "X's" having a different color, i.e., first row of four= "blue", second row or four= "orange" etc....(Blue, Orange, Yellow, Black, Green, White--vary their occurance) to form a table.
----Now------Say the colors of the Xs in the table out loud and as quickly as possible.
Second: Then in create another table and list the name of the colors as a word i.e., write "blue" then the next word i.e., red, then yellow ---but color the "word blue" red and the "word red" blue...etc...so that each of the named colors is not colored the same as it's name.
---Now---name the colors of the words you listed in the two columns as quickly as you can Remember, do not read the words themselves but rather call out the colors of type you see....
Many people take longer to complete the second test because of what is known as the "Stroop effect" (look it up)
---what you have just demonstrated is how two psychological processes running in parallel collide with each other---i.e., your attention resources---are strained---since you are trying to combine a routine, automated task (reading has been so well learned that it runs automatically) with one that demands conscious control---it's called interference or the "Stroop effect"
Balance---a learned task that normally runs automatically---with little conscious effort---now must be consciously controlled---with an inner ear injury---wallah----welcome to the "Stroop effect"
---more then you ever wanted to know---certainly more then I ever did!!!!
What a piece of work this junk is.........
Vision(40%),Vestibular(30%), Proprioception(30%) 
