Contribution of the anterior insula to temporal auditory processing deficits in developmental dyslexia

Abstract

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 on presentation rate, fMRI measurements were performed in 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 an 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 on 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, in 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 an important neural correlate of deficient temporal processing of speech and nonspeech sounds in dyslexia.

The contribution(s) of the insula to speech production: a review of the clinical and functional imaging literature

“…Besides the production of verbal utterances, there is some evidence for participation of the anterior insula in speech-related perceptual functions. Thus, fMRI measurements during application (passive listening task) of isochronous synthetic click trains or syllable repetitions (range 2-6 Hz) revealed hemodynamic insular activation to depend upon presentation rate (Ackermann et al 2001;Steinbrink et al 2009). More specifically, BOLD responses increased/decreased at the left/right side as a function of click frequency and, thus, resembled high-pass (left side) or low-pass filtered (right side) signal series.…”

“…More specifically, BOLD responses increased/decreased at the left/right side as a function of click frequency and, thus, resembled high-pass (left side) or low-pass filtered (right side) signal series. By contrast to healthy controls, the anterior insula, first, failed to display these rate/response profiles and, second, showed reduced hemodynamic activation under both the speech and nonspeech conditions in subjects with developmental dyslexia (Steinbrink et al 2009). Apparently, thus, the rostral insular is engaged in the temporal processing of auditory stimuli.…”

The role of the human anterior insular cortex in time processing

“…There are some suggestions that the left anterior insula is selectively involved in processing short or rapidly repeated stimuli whereas the right is more active during the processing of slower stimuli (Steinbrink et al 2009;Platel et al 1997; see also the following section). If so, it is possible that discrepancies in the literature concerning lateralization may simply reflect the range of tasks employed.…”

Cognitive levels of performance account for hemispheric lateralisation effects in dyslexic and normally reading children

“…Foster et al, 2002) involvement. Moreover, bilateral anterior insula was observed to be involved in the processing in human speech and non-speech sounds in dyslexia (Steinbrink et al, 2009a). Brain function differences between dyslexic and normally reading persons were also reported for visual processing and visual attention, but data mostly come from electrophysiological studies (e.g.…”