Last week, “At the Beach,”  I discussed many sensory systems that get activated while you lie in the sun, play in the sand or explore in the water.  Today, I focus on the “Mother of all Senses,”  the vestibular system. I state this with great respect. We have vague awareness of this system when we float on a raft.  We have an acute awareness of this system when spinning around on a roller coaster! The vestibular system affects us at almost every level of our neurological being.  It can have an influence on our respiration and heart rate, stimulates alerting responses and especially helps in attempts to reach a state of relaxation. 

So what is this system and how does it work?

The vestibular system actually has a “sense organ.”  It is located in the ear and is very complicated.  It is based in the semicircular canals and inner ear with a variety of sense organs inside.  The fluid inside the ear swishes around in a variety of directions, depending on how you move and the position of your head.  The little hairs (cilia) that “swish” send a message to the brain about the direction of movement.  There are also little crystals called otoliths that have another job, related to the position of the head and a detection of movement, especially speed. 

What does the message do in the brain?

This is where it gets complicated.  The vestibular system is intricately and profusely linked to many other systems in the brain. The eyes and vestibular system work in sync-that’s why your eyes go crazy, moving back and forth (nystagmus) when you are dizzy.  When overstimulated, the message gets down to the brain stem level, which controls autonomic, or very basic physiological responses, such as smooth muscle of the gut, breathing and heart rate.  That’s why you might throw up after one of those spinning rides or when a boat rolls around too much in the high seas.

  

But it’s not all bad!!  Because of its pervasive influence, the vestibular system has an affect on motor coordination, language centers and areas of the brain involved in alerting and organization. Brain studies are still sorting all of this out because we have learned that the brain does not act with just discreet areas for specific tasks.

We know the occipital lobe houses the visual centers and the temporal lobe’s primary job relates to hearing and language.  We parsed out different areas for expressive language and comprehension long ago. What is evolving, is our understanding of the interplay of different brain areas and more diffuse networks that lace throughout the cerebral cortex. Very few scientists could imagine the interplay of brain areas and the diverse integration of these systems decades ago (I might add that Jean Ayres imagined this in the early 60’s). 

One science article sited by the NY Times several years ago described scientists’ amazement when they hooked up subjects heads to electrodes during a language task (sitting with no movement in their chairs) and the area of the brain that fired up the most was the cerebellum.  Up until that point all neuroscientists knew “with confidence” that the only job of the cerebellum related to motor coordination and balance. How could the cerebellum be activated by a language task!!!???

I will share one case study that reflects the amazing and powerful effect of the vestibular system.  This occurred about 20 years ago.

I worked in a progressive special education preschool with children who had significant delays in several areas.  I worked with a little boy; we’ll call him John. I had worked on strengthening his trunk for about a year.  He finally had the motor control and reduced fearfulness of movement, so I was able to put him on a suspended platform swing. I rotated him and he tolerated this well.  So I was able to rotate him fairly vigorously on and off during his 20+ minute session.*

Then John was off to speech in the adjacent classroom. It was an integrated approach: OT first to get his trunk awake and ready so he could attend better and have better postural control for his speech work. A few moments later the speach and language therapist came back into the room flushed with excitment.  “What did you do to John?!”  I got pretty nervous, wondering if there was a problem, since as I mention above, the vestibular system is powerful and has an influence over physiological responses.  “What happened?” I queried? Apparently John started talking like he’d never talked before:  unprompted words with clarity. Somehow the vestibular system gave the “push” needed to connect some missing link in language pathways.  The language stuck.  John’s speech and language moved on to a new level!

Some people crave vestibular input in the form of spinning, etc.  Amusement parks, fast cars and crazy rides on the high seas lead to a positive rush.  For others, the vestibular system is sensitve and the same input leads to a tough day of nausea and head aches.  There are ways to trick the system; dancers and ice skaters are expert at this (that vision connection).  More on that another day ...

What does this have to do with The Motor Story?  The vestibular system, like the proprioceptive system is triggered by movement. On the beach theme, I’ll review a few simple ways you trigger alerting/stimulating and relaxation responses.

1. 1. Rolling down a hill  (Stimulating)
   

2. 2. Floating on a raft-gently moving/rocking (Relaxing)
   

3. 3. Floating on a raft-fast  moving/rocking   (Stimulating)
   

4. 4. Surfing-speeding fast down a wave  (Stimulating)
   

5. 5. Boogie boarding, etc.  (Stimulating)
   

Floating on this simple raft can be relaxing.  Crashing through the waves while boogie boarding is “excitatory” and “wakes up” the nervous system.  No waves?  Manually bouncing, rocking and pulling the raft in various directions at rapid speeds can elicit the same response.

A hammock can be very relaxing as it sways slowly back and forth.  Mix it up with faster swinging, and tipping and the neurological system gets highly activated!

 

*Rotation can have adverse effects so it is important to get advice from a professional before spinning a child. On the playground, let the child take the lead in determining how much spinning can be toerated. Never impose rotation on the unwilling!

For a comprehensive definition of Otoliths:

http://en.wikipedia.org/wiki/Otolith

And an integrated view of the semicircular canals and the otolith system:

http://www.ncbi.nlm.nih.gov/books/NBK10863/

                                 

 

This is a BIG TOPIC!  More on the vestibular system next posting with more activities and how they wake us up and clam us down!

                                              

                                       

             

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                 Your Child’s Motor Development Story

                                     by Jill Mays

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