Contribution of the Anterior Insula to Temporal Auditory Processing Deficits in Developmental Dyslexia

Developmental dyslexia has been assumed to arise from general auditory deficits, compromising rapid temporal integration both Of linguistic and nonlinguistic acoustic stimuli. Because the effort of auditory temporal processing of speech and nonspeech test materials may depend oil presentation rate, fMRI measurements were performed ill dyslexics and controls during passive listening to series of syllable and click Sounds, using a parametric approach. Controls showed a decrease of hemodynamic brain activation within the right and all increase within the left anterior insula as a function Of the presentation rate both of click as well as syllable trains. By contrast, dyslexics exhibited this profile of hemodynamic responses under the nonspeech condition only. As concerns syllables, activation in dyslexics did not depend oil presentation rate. Moreover, a subtraction analysis of hemodynamic main effects across conditions and groups revealed decreased activation both of the left and right anterior insula in dyslexics compared to controls during application both of click and syllables. These results indicate, ill line with preceding studies, that the insula of both hemispheres is involved in auditory temporal processing of nonlinguistic auditory stimuli and demonstrate, furthermore, that these operations of intrasylvian cortex also extend to the linguistic domain. In addition, Our data Suggest that the anterior insula represents all important neural correlate of deficient temporal processing of speech and nonspeech sounds, ill dyslexia. Hum Brain Mapp 30:2401-2411, 2009. (c) 2008 Wiley-Liss, Inc.