Abstract
BackgroundIndividuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). To further elucidate the brain mechanisms underlying this extraordinary skill, functional magnetic resonance imaging (fMRI) was performed in blind subjects of varying ultra-fast speech comprehension capabilities and sighted individuals while listening to sentence utterances of a moderately fast (8 syl/s) or ultra-fast (16 syl/s) syllabic rate.ResultsBesides left inferior frontal gyrus (IFG), bilateral posterior superior temporal sulcus (pSTS) and left supplementary motor area (SMA), blind people highly proficient in ultra-fast speech perception showed significant hemodynamic activation of right-hemispheric primary visual cortex (V1), contralateral fusiform gyrus (FG), and bilateral pulvinar (Pv).ConclusionsPresumably, FG supports the left-hemispheric perisylvian “language network”, i.e., IFG and superior temporal lobe, during the (segmental) sequencing of verbal utterances whereas the collaboration of bilateral pulvinar, right auditory cortex, and ipsilateral V1 implements a signal-driven timing mechanism related to syllabic (suprasegmental) modulation of the speech signal. These data structures, conveyed via left SMA to the perisylvian “language zones”, might facilitate – under time-critical conditions – the consolidation of linguistic information at the level of verbal working memory.
Highlights
Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables per second - exceeding by far the maximum performance level of normal-sighted listeners
Using functional magnetic resonance imaging, a preceding single-case study of our group first documented significant hemodynamic activation of right-hemispheric primary visual cortex (V1) and contralateral fusiform gyrus (FG) in a blind university student with high ultrafast speech perception capabilities during application of compressed verbal utterances (16 syl/s) whereas, by contrast, similar responses did not emerge in a series of sighted control subjects [19]
Intelligible verbal utterances, i.e., ultra-fast speech in case of skilled blind and moderately fast sentences in case of all participants, elicited significant hemodynamic responses within the superior/middle temporal gyri and sulci, lefthemispheric inferior frontal gyrus (IFG), left supplementary motor area (SMA), left precentral gyrus (PrCG), as well as the cerebellum
Summary
Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). As a further “feat” within the realm of acoustic communication, analogous, conceivably, to the fast-reading capabilities of sighted individuals, repeated exposure to accelerated verbal utterances may enable blind people to understand spoken language at speaking rates of up to 22 syllables (syl) per second – an accomplishment exceeding by far the upper limits of untrained subjects Using functional magnetic resonance imaging (fMRI), a preceding single-case study of our group first documented significant hemodynamic activation of right-hemispheric primary visual cortex (V1) and contralateral fusiform gyrus (FG) in a blind university student with high ultrafast speech perception capabilities during application of compressed verbal utterances (16 syl/s) whereas, by contrast, similar responses did not emerge in a series of sighted control subjects [19]
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