SUBADDITIVE AUDITORY CORTEX ACTIVATION TO AUDIOVISUAL SPEECH MEASURED WITH FUNCTIONAL NEAR INFRARED SPECTROSCOPY
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2013-09-01
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en
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To understand audiovisual speech, multisensory information from different parts of the brain needs to be integrated. Several non-invasive techniques can be used to study the neural processes underlying such integration, and are useful to study speech processing in healthy adults. Most of these techniques, however, are limited when it comes to children or subjects with electro-magnetic implants.Here, we asses multisensory integration of audiovisual speech in auditory cortex with functional near-infrared spectroscopy (FNIRS). We use unisensory (audio/video only) or multisensory (audiovisual) speech stimuli in a passive experiment. We find weak (0.2 μM concentration change) evoked responses of auditory cortex to both unisensory and multisensory stimuli, in both hemispheres across participants. Modeling the evoked response was done using a canonical hemodynamic response function and a Bayesian approach to calculation regression coefficients. We demonstrate some sub-additive multisensory enhancement for both oxyhemoglobin and deoxyhemoglobin measurements. Our experiments show that FNIRS is able to determine multisensory integration within the brain on a group level for a selection of participants. However, problems using FNIRS in the current set up were high levels of measurement noise, high response variance between sessions and unknown physiological artefacts. This lead us to conclude that FNIRS in its current form is not a feasible tool for measuring CI-patients and infants.
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Faculteit der Sociale Wetenschappen