Friday, March 14, 2008

It's before the task, stupid!

Weber-Fox's team has looked at school-age children's brains while performing a visual rhyming task. They used ERP (event-related potential or evoked potential) which is a range of methods that record electrical activities in form of potentials in the brain due to a stimulus: see picture above. They want to understand why kids who stutter have lower accuracy on rhyming judgment (not sure exactly what they did; I guess the kids were given two words on a screen and had to judge quickly whether the words rhyme or not). They did not find any differences in electrical activity for the task, but they found atypical activities before the task itself. This observation makes sense to me. Many of the non-speech related deficiencies like in dual tasks or rhyming judgment are probably due to a sub-optimal coordination between the different brain regions, which is probably due to the brain having to compensate for some failing region(s). Think of a transport system of a big city. Imagine a bridge must close and be re-built. The impact on the transport system can be dramatic and impact not only the local area. For example, the heavy lorries now have to use another bridge which is less equipped to handle heavy traffic and therefore fast deteriorates, too. Or there are suddenly traffic jams in unexpected parts of the city, and for example disrupt the functioning of a big factory or hospital.

Atypical neural functions underlying phonological processing and silent rehearsal in children who stutter.

Speech, Language, & Hearing Sciences, Purdue University, USA.

Phonological processing was examined in school-age children who stutter (CWS) by assessing their performance and recording event-related brain potentials (ERPs) in a visual rhyming task. CWS had lower accuracy on rhyming judgments, but the cognitive processes that mediate the comparisons of the phonological representations of words, as indexed by the rhyming effect (RE) ERP, were similar for the stuttering and normally fluent groups. Thus the lower behavioral accuracy of rhyming judgments by the CWS could not be attributed to that particular stage of processing. Instead, the neural functions for processes preceding the RE, indexed by the N400 and CNV elicited by the primes and the N400 elicited by the targets, suggest atypical processing that may have resulted in less efficient, less accurate rhyming judgment for the CWS. Based on the present results, it seems likely that the neural processes related to phonological rehearsal and target word anticipation, as indexed by the CNV, are distinctive for CWS at this age. Further, it is likely that the relative contributions of the left and right hemispheres differ in CWS in the stage of processing when linguistic integration occurs, as indexed by the N400. Taken together, these results suggest that CWS may be less able to form and retain a stable neural representation of the prime onset and rime as they anticipate the target presentation, which may lead to lower rhyming judgment accuracy.

1 comment:

Anonymous said...

Uhm. I have always been extraordinary good in things like rhyming and other speech-related tasks...