Perception of Ultra-Fast Speech by a Blind Listener – Does He Use His Visual System?

We investigated if a blind person uses his visual system to understand moderately fast speech (8 syll/sec) and ultra-fast speech (16 syll/sec) based on texts spoken by a male person and produced by a speech synthesis, respectively. Whereas the blind subject had no problems understanding ultra-fast speech, six sighted control subjects were not able to understand it. Functional magnetic resonance imaging (fMRI) of the brain activity proved that moderately fast speech activated posterior and anterior 'language zones ' in all subjects. Regarding ultra-fast tokens, the controls showed exclusive activation of supratemporal regions whereas the blind participant exhibited enhanced left inferior frontal and temporoparietal responses as well as significant hemodynamic activation of left fusiform gyrus (FG) and right primary visual cortex. Since left FG is known to be involved in phonological processing, this structure, presumably, provides the functional link between the central-auditory and-visual systems.