Browsing by Author "Crewther, David"

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    Evidence for enhanced multisensory facilitation with stimulus relevance: An electrophysiological investigation
    (PLOS, 2013-01-23) Baratchu, Ayla; Freestone, Dean; Innes-Brown, Hamish; Crewther, David; Crewther, Sheila
    Currently debate exists relating to the interplay between multisensory processes and bottom-up and top-down influences. However, few studies have looked at neural responses to newly paired audiovisual stimuli that differ in their prescribed relevance. For such newly associated audiovisual stimuli, optimal facilitation of motor actions was observed only when both components of the audiovisual stimuli were targets. Relevant auditory stimuli were found to significantly increase the amplitudes of the event-related potentials at the occipital pole during the first 100 ms post-stimulus onset, though this early integration was not predictive of multisensory facilitation. Activity related to multisensory behavioral facilitation was observed approximately 166 ms post-stimulus, at left central and occipital sites. Furthermore, optimal multisensory facilitation was found to be associated with a latency shift of induced oscillations in the beta range (14–30 Hz) at right hemisphere parietal scalp regions. These findings demonstrate the importance of stimulus relevance to multisensory processing by providing the first evidence that the neural processes underlying multisensory integration are modulated by the relevance of the stimuli being combined. We also provide evidence that such facilitation may be mediated by changes in neural synchronization in occipital and centro-parietal neural populations at early and late stages of neural processing that coincided with stimulus selection, and the preparation and initiation of motor action.
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    Susceptibility to the flash-beep illusion is increased in children compared to adults
    (Wiley, 2011-09) Innes-Brown, Hamish; Baratchu, Ayla; Shivdasani, Mohit; Crewther, David; Grayden, David; Paolini, Antonio
    Audio-visual integration was studied in children aged 8-17 (N=30) and adults (N=22) using the “flash-beep illusion” paradigm, where the presentation of two beeps causes a single flash to be perceived as two flashes (fission illusion), and a single beep causes two flashes to be perceived as one flash (fusion illusion). Children reported significantly more fission illusions than adults, indicating that auditory and visual information was integrated more often, and less selectivity than in adults. Within either group, illusion reports did not correlate with either age or motor coordination measures. The current results show that the form of multisensory integration indexed by the illusion is slow to mature in normally-developing children.