Thursday, November 22, 2007

Recovered and persistent kids show abnormalities

I have already spoken about the important brain imaging work by Soo-Eun Chang from Christy Ludlow's group at NIH, and the department of Speech and Hearing Sciences at the University of Illinois at Urbana-Champaign. Let me put it up again as it is very important. They looked at the brain of children who do not stutter, who recovered from stuttering, and who did not recover:
Previous imaging studies in adults with persistent stuttering found left white matter deficiencies and reversed right-left asymmetries compared to fluent controls. We hypothesized that similar differences might be present indicating brain development differences in children at risk of stuttering. Optimized voxel-based morphometry compared gray matter volume (GMV) and diffusion tensor imaging measured fractional anisotropy (FA) in white matter tracts in 3 groups: children with persistent stuttering, children recovered from stuttering, and fluent peers.
The results:
Both the persistent stuttering and recovered groups had reduced GMV from normal in speech-relevant regions: the left inferior frontal gyrus and bilateral temporal regions. Reduced FA was found in the left white matter tracts underlying the motor regions for face and larynx in the persistent stuttering group. Contrary to previous findings in adults who stutter, no increases were found in the right hemisphere speech regions in stuttering or recovered children and no differences in right-left asymmetries. Instead, a risk for childhood stuttering was associated with deficiencies in left gray matter volume while reduced white matter integrity in the left hemisphere speech system was associated with persistent stuttering. Anatomical increases in right hemisphere structures previously found in adults who stutter may have resulted from a lifetime of stuttering. These findings point to the importance of considering the role of neuroplasticity during development when studying persistent forms of developmental disorders in adults.
Let me rephrase in common language:

1) Brains of both recovered and persistent stuttering children show structural abnormalities.

2) Right side abnormalities in volume increases found in adults are absent in (recovered and persistent) stuttering children.

3) Stuttering in children is associated with left side abnormalities, and persistence specifically associated to white matter abnormalities.

Let me lean out of the window by saying that

1) The existence of right side abnormalities in volume increases in stuttering adults but not in children strongly suggests compensatory activities that made some right side regions grow.

2) These regions are mainly to blame for relapse in adults because they are more or less hard-wired.


Kostja said...

I think this is what everybody was expected:
abnormalities in kids stuttering braines, and abnormality in right hemisphere to be secondory to stuttering as compensation mechanism.

Tom Weidig said...

Yes, but what is really interesting is that recovered kids also have the left side abnormality.

So over the years, they will also show right side abnormalities as they keep on compensating.

But do they differently?

Chris said...

We need more research like this. I don't think it would take very long to find the real anatomical sources of stuttering (maybe there are more than one...) in the brain if and only if there were a few more famous researchers being interested in stammering.