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Abstract:
It is proposed that speech perception is not only a property
of the auditory modality but that it is carried out by global
mappings between auditory, motor, visual, and orosensory
modalities. In this experiment global processes underlying speech
are investigated in a single individual by means of scalp
recorded gamma band electrical brain activity. Neural activity
underlying the enhancement of speech intelligibility by
visualization of speech facial motion under conditions in which
the auditory speech signal has been degraded by noise was found
to be localized primarily to auditory cortex. Suggesting that
visual information can influence auditory speech processing.
Furthermore, speech motor areas of the brain were found to be
more active under conditions in which speech is degraded by
noise, irrespective of facial motion, suggesting that these areas
may be involved with global processes that attempt to facilitate
speech perception. Neural activity involved with the perceptual
processes underlying the experimental conditions was determined
by decomposition of the single sweep evoked responses by
independent component analysis. The activity of the relevant
components was localized to the surface of the cortex using
current source density and dipole analysis constrained by
anatomical MRI data.
A version of this article titled "Multimodal Contribution to
Speech Perception Revealed by Independent Component Analysis: A
Single-Sweep EEG Case Study", has been submitted to
Cognitive Brain Research.
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