The perceptual system: That little time-machine

Abstract

Various physical circumstances (for instance, the fact that light and sound do not travel at the same speed) and/or physiological factors (such as the fact that auditory signals are initially processed more rapidly than visual signals) give rise to small asynchronies between sensory signals pertaining to a specific multisensory event. Considering the large amount of sensory stimulation that bombards our senses at any given time, being able to re-group sensory signals that belong to the same event (even if they arrive asynchronously) can be highly adaptative. Indeed, the human brain is by-and-large able to maintain a simultaneous and coherent perception of the proximal events that occur in the environment. How is this achieved? Two recently discovered phenomena –temporal ventriloquism (where the presence of a stimulus in one modality influences the perceived time of occurrence of a stimulus in another modality) and temporal recalibration (where the brain realigns asynchronous signals from different sensory modalities)– confirm that the way in which the human brain maintains synchrony is more active and flexible than previously thought.