Monday, June 21, 2010

Bigger disconnect will not correlate strongly to severity

ig88sir asks:
Does anyone think that a bigger disconnect (i.e.,weaker myelin sheath) has a correlation for stuttering severity? It is a naive simplification but seems to make sense to me. They should do imaging with mild and severe PWS to find out.
 I hold the opposite opinion:
  1. Two different dynamics are affecting severity of stuttering. 
    1. The frequency and length of delays in speech initiation due to neurobiological deficits.
    2. The instinctive reactions to speech delays, and acquisition of learned behaviours and cognitive schemes, which can also impact neurobiology.
    3. Factor one might well be directly affected by the disconnect, but a disconnect is only one and probably not even the most important factor in shaping the reaction and re-enforcements.
  2. A slight disconnect might actually make the delays worse, because the brain either
    1. does not compensate neurobiologically speaking, or
    2. compensates but the weak route is still active, so there is interference between two routes.
  3. A severe or full disconnect might force the brain to compensate leading to temporary developmental issues but in the long term that compensatory route is working fine, and there is no interference from the bad fiber connections.
  4. The brain imaging studies show a significant overlap between the pws group and controls. Some controls have a lower fiber coherence than some stuttering people. The difference is also apparent in the population, i.e. the average coherence between the two groups.
  5. The NIH study in recovered stutterers found that the recovered ones had more structural abnormality.
  6. The genetic studies (including the twin studies, I think) have not found a strong correlation between the severity of twins who stutter.
So I would not be surprised that there is no strong correlation between disconnect and severity.


The Stuttering Comedian... said...

I had a really important phone call to make --- A really big one. So I made the call and had a bout of very severe stuttering and the person on the other end hung up and disconnected from me.

This confirms absolutely there is a very, very strong and direct correlation between disconnect and severity...I don't care what genetic or brain imaging studies may say!

Unknown said...

Obviously the right side compensation is the cause of stuttering (rather than a neighboring left hemisphere region). But what are the mechanics of a late (PDS) onset? I was 12 when I started stuttering and I know PWS who started at 14 and even 18. Is it due to the capacity and demand model? Environmental factors must play a role as some people in families that have the stuttering genes never become stutterers. Can a high risk child acquire stuttering if the right elements are in place? I spent extended time around a CWS when I became a CWS. It is as if my brain decided to shift itself around in a few days and then fix itself in stutter mode.

ig88sir said...

Can anyone explain how a late onset completely destroys a previous stable system even when going back to low stress-demand situations? I can almost fathom that when the stress/load is large enough the system jams and breaks down AT THAT LEVEL but why does the system break permanently in the previous lower stress/load levels? Is there a physical rewiring that sets due to the low plasticity? Is it like a breaking dam that once broken is never fixed? Any thoughts?