Friday, February 12, 2010

Genetics FAQ: Why fluctuation in symptoms if biological?

Ivan wrote on STUTT-L
... how exactly do these genes work? Can they be turned on and off? Something I consistently observed is that I am perfectly fluent when alone, but the moment someone enters the room, in a split second, the stuttering comes. If we assume the research is accurate, this seems to suggest that the gene is not always on. It has to be triggered...
There is no paradox.

Let me start with an analogy.

Imagine a car factory producing car batteries that work well in all weather conditions. They have instructions on how to build these batteries. (= All-weather battery gene)

Now, there is some mix-up in the production process
and the instructions have changed. (= mutated all-weather battery gene)

Result: Cars work well in warm climates like California, but fail to work in cold climates like Montreal.

Interpretation: The mutation has led to a lower-capacity (in terms of weather) leading to INCONSISTENT performance.

A clever guy says: Yes, but my battery also doesn't work, but I am in Atlanta where it is warm. You are wrong.

Interpretation: Atlanta has high humidity whereas California has not, and this is also a contributing factors.

Another analogy: Earthquake in Haiti.

Why is there so much damage? because the houses were built with laced concrete (=mutated concrete gene), and a strong shock lets the system break down.

 And on top, learned behaviours, cognitive beliefs, and the environment modulate the frequency and severity of stuttering events.


Rafael Madeira said...

Yes. The genetic part is what enables stuttering. How the stutter is manifested is subjected to the environment. Like any other genetic propensity.

Triumph said...

I totally agree with that, because I do beleive, there is actually no more logical reason.

Mark B. said...

This is an understandable question for someone without genetic training. Let's step back for a moment. Many people get nervous about speaking, but only stutterers stutter. So nervousness or anxiety doesn't cause stuttering. Stuttering is a threshold condition. Stand on one side, no stuttering - stand on the other, stuttering occurs. Our anxiety can shift the threshold, but is not a cause.

Stuttering is typical of many conditions that have already been shown to have a genetic basis. If I didn't know any of the past genetic evidence on stuttering, I would just assume that it would be found.

Let's be clear. A gene doesn't "cause" stuttering. Genes just transfer heritable information from one generation to the next. In the case of the new Drayna research, the "stuttering gene" codes for the production of a protein, and in this case, the protein has a functional difference - it won't work entirely as intended. We still don't know what the "cause" of stuttering is in this case.

Peter Louw said...

It seems as if the elephant is in the room again, the elephant being the stress factor. Stress is a contributory cause of stuttering, not a main or direct cause. Stress impacts on some defective organic component, and the result is stuttering. The organic defect is the result of genetics. So the genetic research is valuable. Makes good sense to me. Regards.

ig88sir said...

After the genetics have made their damage (low white matter density in left hemisphere speech area) the brain of a non recovered PWS uses the right hemisphere to compensate for the left (when in low stress situations).

Analogy: think of each hemisphere as a CPU of a computer. The brain is a dual core processor computer! But one of them is broken by a variable percentage that corresponds to the severity of stuttering. The right CPU processes emotions, anxieties and the left CPU processes speech motor control. When there are no emotions and anxieties the right CPU is idle and free to use for the task of speech motor control. So alone in a room a PWS is fluent (most of the time). The right CPU can take over for the bad left CPU. Under stress the right CPU is maxed out of resources and needs help from the left CPU but alas.. the left is damaged and at low capacity. Stuttering ensures.
Again I am no expert..