Cortical processes underlying the effects of static sound timing on perceived visual speed

It is well known that the timing of brief static sounds can alter different aspects of visual motion perception. For instance, previous studies have shown that time intervals demarcated by brief sounds can modulate perceived visual speed such that apparent motions with short auditory time intervals are typically perceived as faster than those with long time intervals. Yet, little is known about the principles and cortical processes underlying such effects of auditory timing. Using a speed judgment paradigm combined with EEG recording, we aimed to identify when and where in the cortex auditory timing takes place for motion processing. Our results indicated significant effects of auditory timing over the medial parieto-occipital and parietal, right centro-parietal, and frontal scalp sites. In addition, these effects were not restricted to a single ERP component and we observed both significant changes in early and late components. Therefore, our findings here suggest that auditory timing may take place at both early and late stages of motion processing and its influences on motion perception may be the outcome of the dynamic interplay between different cortical regions. Together with accumulating evidence, these findings also support the notion that audiovisual integration is a multistage process and it may be achieved through more diversified processes than previously thought.