This study examined visuotactile cross-modal interactions in the identification of tactile stimuli. In Experiment 1, participants were required to discriminate the orientation of tactile target stimuli (line segments with left and right diagonal orientations) presented at the tip of the participant's left index finger via an Optacon, while trying to ignore a task-irrelevant visual diagonal line presented with a 200-ms or 700-ms stimulus onset asynchrony (SOA). The results show that the participants responded faster when the orientation of the tactile stimuli were congruent with the orientation of the visual stimuli than when they were incongruent in the 200-ms SOA condition. To assess at what level of processing the reaction time advantage obtained with congruent orientation trials takes place, Experiment 2 served as a replication of Experiment 1 with somatosensory event-related brain potential (ERP) recordings. ERP effects of orientation congruency were observed between 200 and 350 ms post-stimulus, suggesting that visuotactile cross-modal interactions may occur at intermediate perceptual-cognitive stages rather than at early sensory-specific or late motor-related stages.
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