Audiovisual Temporal Recalibration:Mechanisms Of Spatial Specific And Object Specific Processing

Time is different from other dimensions, and temporal awareness differs from other sensory awareness. Time and consciousness have always attracted philosophers and mind-searcher since ancient Greece, but questions still remain to be solved and continually baffles modern philosophers and psychologists that where temporal consciousness arises, specifically, how we perceive and are aware of time, which loci in brain is the home of such awareness, the essence of temporal awareness and its relationship with free will. Time illusion refers to the inconsistency between perceived time and physical time, including temporal duration and order illusion. Compression of time after adaptation and oddball stimuli effect in repeated series could be sorted as the former type while temporal ventriloquism and temporal recalibration be the latter. These time illusions demonstrate the ability of our brain to adaptively response to changing environment, as well as kind of perceptual learning ability in time dimension.Our present study mainly focused on one temporal order illusion i.e. temporal recalibration. Given the distinct physical and neural transmission speed(light travels faster than sound in air), the perceived timing of visual and auditory stimulus are commonly disconcert with each other, even cross stimuli from a common event could delay each other in mind. Temporal recalibration is the ability that brain adapts such minor delay between cross modal information. In lab, after exposed to asynchrony stimuli, the measured point of subjective simultaneity(PSS) would shift towards the temporal delay between successive AV stimuli.Two goals was set in present study, one is to explore whether there exist two specific processing in temporal recalibration, i.e.(1)spatial reference regardless of stimuli feature within,(2)object reference regardless of its position, the other is to reveal the underlying mechanism of these two processing. Here two experiments were included, in Expl,"exposure-test" paradigm was adopted and simple audiovisual stimuli with tones prsenting by laudspeaker was used. In exposure phase, two distinct couples of blob and tone alternated in left and right side of screen for a few minutes with one couple asynchrony and the other synchrony, and in test phase either couple was removed to its contralateral position to distinguish these two specific processing with joint task to measure low and high boundary and PSS changes. Exp2was similar with Expl except that a reaction time task was used to measure the perceptual latency changes post adaptation.Our results revealed that:(1) Whatever lateral position, post exposure to A leading and V leading conditions, PSS and boundaries both shifted to the polarity of temporal delay, which was more significant in spatial specific processing; comparing V leading condition with synchrony condition, no significant boundaries shifts were found in each position while between A leading and synchrony condition significant "vision first to synchrony" boundary shift were observed in adapted asynchrony position without comparable significant boundary shift on adapted asynchrony AV stimuli.(2) Whatever speicfic processing, no auditary perceptual latency changes were found. But for visual latency, different effects were exhibited:no significant changes in spatial specific processing were found, but contrary to the hypothesis of perceptual changes, compared with V leading and synchrony condition, visual latency post A leading condition significantly prolonged rather than contracted in object specific processing.(3) Two specific processing known as spatial specific and object specific processing underlie temporal recalibration. Both processing relate to criterion shifts rather than perceptual latency changes.