Audiovisual temporal recalibration occurs independently at two different time scales

Abstract

Combining signals across the senses improves precision and speed of perception, although this multisensory benefit declines for asynchronous signals. Multisensory events may produce synchronized stimuli at source but asynchronies inevitably arise due to distance, intensity, attention and neural latencies. Temporal recalibration is an adaptive phenomenon that serves to perceptually realign physically asynchronous signals. Recently, it was discovered that temporal recalibration occurs far more rapidly than previously thought and does not require minutes of adaptation. Using a classical audiovisual simultaneity task and a series of brief flashes and tones varying in onset asynchrony, perceived simultaneity on a given trial was found to shift in the direction of the preceding trial’s asynchrony. Here we examine whether this inter-trial recalibration reflects the same process as prolonged adaptation by combining both paradigms: participants adapted to a fixed temporal lag for several minutes followed by a rapid series of test trials requiring a synchrony judgment. Interestingly, we find evidence of recalibration from prolonged adaptation and inter-trial recalibration within a single experiment. We show a dissociation in which sustained adaptation produces a large but decaying recalibration effect whilst inter-trial recalibration produces large transient effects whose sign matches that of the previous trial.

A Matched Comparison Across Three Different Sensory Pairs of Cross-Modal Temporal Recalibration From Sustained and Transient Adaptation

“…The results are plotted in Figure 5 and show very clearly that temporal recalibration arising from inter-trial adaptation is strikingly consistent throughout the test period. This was shown recently for inter-trial recalibration to AV asynchrony (Van der Burg, Alais, et al., 2015). Here, we replicate that effect for AV stimuli and extend it to AT inter-trial recalibration.…”

“…Figures 4 and 5). For the AV combination, both the recalibration magnitude and its sustained pattern are consistent with our earlier reports conducted with non-collocated stimuli (Van der Burg et al., 2013; Van der Burg, Alais, et al., 2015). The current results complement those earlier reports in showing that the effect also occurs when stimuli are collocated, establishing that inter-trial recalibration for AV stimuli occurs without spatial selectivity.…”

“…The advantage of doing so is that it allows comparison across three modality pairings within a standardised design between prolonged and inter-trial adaptation, and in addition, we will do so using the same group of observers and collocated A, V and T stimulus components for all conditions. This will establish whether rapid recalibration is indeed absent for AT and VT stimuli on a trial-by-trial basis (Van der Burg, Orchard-Mills, et al., 2015) and also clarify that AT and VT recalibration do indeed occur following prolonged adaptation to collocated stimuli. If we do find AT and VT recalibration after prolonged adaptation but no inter-trial recalibration for the same stimulus pairings, this will support the conclusion that two distinct mechanisms underlie temporal recalibration from sustained and transient stimuli.…”

Multisensory perceptual learning is dependent upon task difficulty

“…While passive exposure to asynchronous stimuli has been previously observed to alter the perceptual representation of perceived synchrony, both over the course of many trials (Fujisaki et al 2004; Vroomen et al 2004; Van der Burg et al 2015a) and trial-to-trial (Van der Burg et al 2013; Van der Burg et al 2015b), passive exposure to asynchronous does not seem to enhance temporal acuity. Although these prior studies, along with those studies that observe enhancement of temporal acuity with feedback (Powers et al 2009), suggest that a reinforcement signal was needed to enhance multisensory temporal acuity, the properties of the stimuli employed during perceptual training have not been systematically explored (Powers et al 2009).…”

“…While it is difficult to determine that no change in criterion occurs following perceptual training, recently, it has been suggested that prolonged changes in the calibration of multisensory temporal representations may be elicited primarily from changes in criterion at the higher-order decisional level whereas as transient trial-to-trial changes in multisensory temporal representations (i.e. rapid recalibration) result from changes at low-level sensory processes (Van der Burg et al 2015a). Furthermore, changes at decisional stages of perception have been recognized to contribute to other forms of perceptual learning (Law and Gold 2008; Law and Gold 2010).…”