Saturday, March 21, 2009

Non-speech specific abnormalities

A reader points me to a new article Brain activation abnormalities during speech and non-speech in stuttering speakers by Chang et al. from NIH which re-enforces evidence that there are non-speech specific abnormalities in the brain of people who stutter. Here is the abstract:
Although stuttering is regarded as a speech-specific disorder, there is a growing body of evidence suggesting that subtle abnormalities in the motor planning and execution of non-speech gestures exist in stuttering individuals.We hypothesized that people who stutter (PWS) would differ from fluent controls in their neural responses during motor planning and execution of both speech and non-speech gestures that had auditory targets. Using fMRI with sparse sampling, separate BOLD responses were measured for perception, planning, and fluent production of speech and non-speech vocal tract gestures. During both speech and non-speech perception and planning, PWS had less activation in the frontal and temporoparietal regions relative to controls. During speech and non-speech production, PWS had less activation than the controls in the left superior temporal gyrus (STG) and the left pre-motor areas (BA 6) but greater activation in the right STG, bilateral Heschl's gyrus (HG), insula, putamen, and precentral motor regions (BA 4). Differences in brain activation patterns between PWS and controls were greatest in females and less apparent in males. In conclusion, similar differences in PWS from the controls were found during speech and non-speech; during perception and planning they had reduced activation while during production they had increased activity in the auditory area on the right and decreased activation in the left sensorimotor regions. These results demonstrated that neural activation differences in PWS are not speech-specific.
The evidence for a neurological basis of stuttering is growing. And it does not seem to be restricted to speech function. But why are the abnormalities only showing up clearly at speech? Probably for two reasons: speech exacts a lot from the brain unlike other functions, and disturbed speech provokes a much greater response from the brain, the stutterers, and the environment. And the reponses lead to a feedback with words, events, and people being associated to stuttering behaviours and then these are triggering stuttering again.

More specific comments on the articles are coming soon.


Anonymous said...

I have always known that stuttering is only one of the symptoms of this disorder. Since I started stuttering at the age of 14 (unusually late) I have wondered why so many stutterers and "experts" fail to realize this.

OliverTwix said...
This comment has been removed by the author.
O said...

Sorry, but I don't see what's really new about this...?

Anonymous said...

To me there appears to be several new things about this data. First this study is only one of a few studies that have used short utterance stimuli (which do not normally elicit stuttering) during neuroimaging, which means that any brain activation differences seen in stuttering people were not due to stuttering itself. In other words,even during fluency-evoking tasks resulting in perceptually fluent speech, and even during non-speech, there were brain activation abnormalities, which suggests that stutterers may have a more generalized sensorimotor issue. This idea is not new, but this paper shows empirical evidence that support a neurological basis for it.
Another thing is that this paper says it found differences during perception and planning phases in addition to production. Apart from some MEG studies that showed differences during pre-production phases I think this is the first to show all of these phases in one paper. Should be an interesting read.