I figured it out.

One thing that has frustrated me as I researched SPS has been that I couldn’t connect the macro with the micro.  I know damn well what the macro pattern is (too much noise -> everything is terrible, and also I bump into walls a lot), and I’ve been learning about the micro pattern (auditory, visual, or touch stimulus leads to over-activation of certain areas of the brain), but how did overactivation lead to irritability?    The Threads of Autism (which I’ve since finished) went on and on about teaching people to “organize” sensory input, but it only described the effects of this in macro language (people become more relaxed, more resilient, able to thrive under higher levels of stimulus), but not what that actually looked like in the brain.  Much less why pronating and supinating my wrists in time with my breathing or tapping along my facial nerves was going to accomplish this.

I think I’ve figured it out.  Before I tell you, I want to make it very clear that this is my own personal metaphor, and not something that’s been tested scientifically.  I’m not even sure what it would mean to test it.  But it makes sense to me.

Your/your body’s ultimate goal is to figure out what it should be doing at any given second, and especially if it should be running away from or trying to breed with something.  In order to do that, it tries to work backwards from the sensory input to derive a model of what is actually happening*.  It can then decide how it wants to respond to that thing that is happening.  For example, if you’re wandering through the jungle and hear a twig snap, you would like to know if it’s a delicious herbivore, a hungry tiger, or a human being, and if so, is it from  your tribe or the one you’re at war with.  Past sensory experience is really helpful in this interpretation.  For example, if you’ve heard lots of tigers walking in the jungle, you can pattern match the current sounds against the ones you remember and see how close they are.

But what if it were more basic than that?  We think we just know when and where and how someone is touching us, or how we’re oriented in space, but that is actually something you have to learn.  We don’t notice because it’s mostly done when when we’re very very young, and because it’s done in parts of our brain that we’re not  consciously aware of.  But human brains are actually very plastic, and we devote an extraordinary amount of time and energy to learning how to translate “nerve 43b is firing” to “something happened on my left ring finger.”

My metaphor is as follows:  people with SPS either don’t have the same bank of experiences to pattern match against, or are worse at matching.  So given the same amount of sensory input, it takes them a lot more energy to correctly model the source.  It’s sort of like simplifying a mathematical equation.  If you have something awful with lots of terms you can solve it by hand, but it’s error prone and time consuming.  If you take that same equation and simplify it by removing terms that cancel and grouping like terms together, that same equation can be trivial.

I think the point of the sensory integration exercises is to build up either the database of experiences and/or your skill at simplifying equations.  You can’t give a person every single experience, but you can teach them “this is what stimulus from the trigeminal nerve feels like deep inside your brain.”  This makes it marginally easier to identify, or at least not freak out about, novel stimulus.  It’s like teaching someone about a 3-4-5 triangle.  They’ll not only recognize other 3-4-5 triangles faster, but eventually 6-8-10 and 4.5-6-7.5 as well.

When I started in computational biology, I was all about complex computer simulations.  By my senior year of college, I’d learned to appreciate mathematical models.  They left out details, but that was what let you see the general patterns.  If I’m right, I’m about to undergo the same process for basic sensory data.  And I know I can do it.

*Exception: reflexes