Friday, February 24, 2006

On brain research

I got an email from George D asking me interesting questions on brain imaging, which might also interest you.

George: It seems to me that there have been a few problems with the approach to the research. 1) All of the studies have been done on adult stutterers, and this will always leave open the question of whether the observed differences reflect acquired characteristics - or *learned* behaviours/strategies - or whether they really do reflect inherent, hard-wired neural differences.

The researchers look for across-the-sample CONSISTENT differences. This eliminates individual characteristics like "I use filler", "you have silent blocks". The pathways and activation would not be the same, and so eliminated.

Thus, individual coping strategies should be eliminated, but not systematic ones not e.g. everyone gets more tense. This makes things more difficult, but at the very least shows us what the core of stuttering is.

So what you see are correlations. The interpretation is of course more difficult, but by adding theoretical reasoning, including non-brain findings and varying experimental designs you can start to distinguish between what is a consequence and what a cause. This is currently underway.
George: Obviously, doing brain scans on little children (thus exposing them to radiation) is not ethical.

fMRI does not give out radiation, only a strong magnetic field. I think that researchers are now comfortable scanning younger children. But I dont know the details. Sounds like an interesting post for my blog! :-)
George: Most (if not all) brain imaging appears to have been done with fMRI or PET. PET and fMRI have inherently very limited temporal resolution, and to research stuttering, higher resolution is required because speech/language processing takes place in a matter of milliseconds. One idea is to use PET/fMRI together with magnetoencephalography (MEG), which has excellent temporal resolution. I guess this may already have been done??

Yes, there is a paper by Samelin. See here. But I am also surprised why so little MEG work has been done. I need to find out.
George: The number of imaging studies done on stutterers seems to be small, so the results may not be a true indication. Actually, I don't know whether the number of studies is small, but I suspect that it might be.

No, I have counted more than 10 studies. So it is pretty safe. In any case, it would be highly strange if brain imaging hadnt found any functional difference because our brain is sending the stuttering signal to our muscles. Structural abnormalities is another issue.

See here.

1 comment:

Einar said...

What do you think about the question: Is stuttering a disability? (re: my last blog entry)