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Abstract:
Abstract: Humans use their eyes and their ears to perceive
speech. With functional magnetic resonance imaging (fMRI), we
investigated the claim that silent lipreading activates primary
auditory cortex. In a passive listening task, 1000-Hz pulse tone
stimuli were used to activate primary auditory cortex in hearing
adults. Visible spoken word stimuli were presented to hearing and
prelingually deaf adults with average or better lipreading scores.
In the experimental condition, participants viewed a talker saying
isolated words and indicated when two words in sequence were the
same. In the control task, they viewed a still video frame of the
talker and indicated when two colored shapes above the talker's
nose were the same. 10-mm thick fMRI sections were obtained in
transaxial and coronal orientations at 1.5T. Visible speech
activated the lateral surface of the superior temporal gyrus and
the cortex within the superior temporal sulcus (secondary auditory
cortex) but not the primary auditory cortex. Minimal overlap in
activation sites for the tone and visible speech supports the
conclusion that primary auditory cortex is reserved for processing
acoustic stimuli. Evidence that secondary auditory cortex processes
visual phonetic information, in addition to previous evidence that
it processes auditory information, supports the view that phonetic
perception operates on common acoustic and optical phonetic
stimulus attributes of speech.
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