Enhanced speech perception capabilities in a blind listener are associated with activation of fusiform gyrus and primary visual cortex

Abstract

Blind individuals may learn to understand ultra-fast synthetic speech at a rate of up to about 25 syllables per second (syl)/s, an accomplishment by far exceeding the maximum performance level of normal-sighted listeners (8–10 syl/s). The present study indicates that this exceptional skill engages distinct regions of the central-visual system. Hemodynamic brain activation during listening to moderately- (8 syl/s) and ultra-fast speech (16 syl/s) was measured in a blind individual and six normal-sighted controls. 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 betweeen the central-auditory and -visual systems.

Keywords:

• Auditory processing
• Speech perception
• Synthetic speech
• Speech rate
• fMRI
• Neuroplasticity
• Visual system

This study was supported by the German Research Foundation (DFG; SFB 550/B1). The authors would like to thank Maike Borutta for excellent technical assistance.