Multisensory processes of auditory-visual stimuli onset asynchrony in human cortex

Although the previous study in animal superior colliculus showed several multisensory integrative principles, the extent to these multisensory mechanisms generalize to cortical processes remains to be fully elucidated. The aim of this study was to provide electrophysiological evidence that temporal principle, from animal experiments, is and/or is not applicable in human cerebral cortex. Event-related potentials (ERPs) were recorded from 121 scalp electrodes while subjects performed a forced-choice categorization task: At each trial, the subjects had to indicate which of two objects was presented by pressing one of two keys. The two objects were defined by auditory features alone, visual features alone, or the combination of auditory and visual features. In combination conditions, visual stimulus onset was 15 ms (experiment 1) and 30 ms (experiment 2) earlier than the auditory stimulus onset. Spatiotemporal analysis of ERPs revealed several auditory-visual interaction components that can and/or cannot be explained by previous temporal principle, suggested that crossmodal integration in human cerebral cortex may subserve a different role from that in the superior colliculus and be governed by slightly different rules.