Simultaneity constancy: Unifying the senses across time

What are the consequences of visual and tactile neural processing time differences when combining multisensory information about an event on the body's surface? To investigate this, I measured the point of subjective simultaneity (PSS) for various combinations of stimuli. Generally, as stimuli were closer together in space, they were more likely to be correctly perceived as simultaneous despite differences in processing times, suggesting a compensatory mechanism. I adapted subjects using a method known to shift the PSS of the adapted pair, and looked for an effect on the PSS of other pairs of stimuli as well on the reaction times to individual stimuli. The effect of adaptation on the PSS was inconclusive. However, adaptation had no effect on the reaction times of the individual stimuli, representative of a top-down mechanism. I suggest multiple, parallel, top-down mechanisms with three distinct stages which, together, reduce the computational effort needed to resynchronise stimuli.