Saturday, February 19, 2005

I may have been unfair

I mentioned my theory on liberal mind-readers to my dad, and he emailed back with some very interesting thoughts and information about brains and tendons:

[The nurse] was partly right. ... Some people can mentally block a deep tendon reflex, like a patellar reflex. I've encountered lots and lots of people who could.

When you thump certain tendons, like the knee one, it stretches it, which stimulates proprioceptors in the tendon, which fire a signal up the nerve to the spine and then to the brain. With deep tendon (or myotatic) reflexes, the spine fires a motor signal back and makes the quadricept muscles contract and slightly extend the knee before the brain can interpret the signal, decide not to contract the quadricept and send a motor signal back. But some people anticipating the thump to the patellar tendon already have the signal on the way before the reflex can happen.

But... the theory is that a brain can only actively deal with three signals, give or take depending on the individual, at a time. Like three sensory ones, coming from some place in the body to the brain; or three motor ones sent from the brain to some muscle in the body; or some combination of sensory and motor signals.

Brains give priority to motor signals. That's why when someone is playing a rough, active, intense sport where they have to notice and respond to many things at once, they don't notice all the bumps and bruises and associated owies and pain util they are done playing.

So... if you occupy a brain with three motor tasks, it will ignore insignificant sensory signals, like the signal sent from the proprioceptors in the patellar tendon after it is slightly and briefly stretched by being thumped, and not send a motor signal to block the reflex triggered by the signal fired back from the spine.

What I do is give the person more than three motor functions to do at the same time. "Hold your arms with your elbows out to the sides parallel to the floor (one task requiring a signal from the brain to a muscle), hook your fingers together in front of you (another signal from brain to a muscle), focus your eyes on the orange flower in the picture on the wall to your right (signal from brain to neck and eye muscles), and pull real hard with your hands (more signals to muscles. Many people actually can't do all those things at once. They're maxed out.)." Then I thump their knee. It never didn't work.

They teach women the same theory for natural childbirth, to block pain. It's called psychoprophylaxis (mind blocking). They have them breath in certain patterns and count fingers on someone else's hands.
So I guess we'll have to see if he can make my knees bounce.


At 3:56 PM, Anonymous Anonymous said...

I must be one who "max's out" with few motor signals. My dad told me I couldn't walk and chew gum at the same time.


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