title: Tracking the speech signal--time-locked MEG signals during perception of ultra-fast and moderately fast speech in blind and in sighted listeners.
abstract: Blind people can learn to understand speech at ultra-high syllable rates (ca. 20 syllables/s), a capability associated with hemodynamic activation of the central-visual system. To further elucidate the neural mechanisms underlying this skill, magnetoencephalographic (MEG) measurements during listening to sentence utterances were cross-correlated with time courses derived from the speech signal (envelope, syllable onsets and pitch periodicity) to capture phase-locked MEG components (14 blind, 12 sighted subjects; speech rate=8 or 16 syllables/s, pre-defined source regions: auditory and visual cortex, inferior frontal gyrus). Blind individuals showed stronger phase locking in auditory cortex than sighted controls, and right-hemisphere visual cortex activity correlated with syllable onsets in case of ultra-fast speech. Furthermore, inferior-frontal MEG components time-locked to pitch periodicity displayed opposite lateralization effects in sighted (towards right hemisphere) and blind subjects (left). Thus, ultra-fast speech comprehension in blind individuals appears associated with changes in early signal-related processing mechanisms both within and outside the central-auditory terrain.
authors: Department of General Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Germany. ingo.hertrich@uni-tuebingen.de
authors: Ingo
authors: I
authors: Hertrich
authors: Susanne
authors: S
authors: Dietrich
authors: Hermann
authors: H
authors: Ackermann
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology; D001766:Blindness / Q000503:physiopathology*; D001931:Brain Mapping; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008962:Models, Theoretical; D009473:Neuronal Plasticity / Q000502:physiology*; D010898:Pitch Perception / Q000502:physiology; D011578:Psycholinguistics; D011930:Reaction Time / Q000502:physiology; D013060:Speech; D013067:Speech Perception / Q000502:physiology*; D013997:Time Factors; D014793:Visual Cortex / Q000502:physiology