Abstract
BackgroundAn outstanding question in sensory neuroscience is whether the perceived timing of events is mediated by a central supra-modal timing mechanism, or multiple modality-specific systems. We use a perceptual learning paradigm to address this question.Methodology/Principal FindingsThree groups were trained daily for 10 sessions on an auditory, a visual or a combined audiovisual temporal order judgment (TOJ). Groups were pre-tested on a range TOJ tasks within and between their group modality prior to learning so that transfer of any learning from the trained task could be measured by post-testing other tasks. Robust TOJ learning (reduced temporal order discrimination thresholds) occurred for all groups, although auditory learning (dichotic 500/2000 Hz tones) was slightly weaker than visual learning (lateralised grating patches). Crossmodal TOJs also displayed robust learning. Post-testing revealed that improvements in temporal resolution acquired during visual learning transferred within modality to other retinotopic locations and orientations, but not to auditory or crossmodal tasks. Auditory learning did not transfer to visual or crossmodal tasks, and neither did it transfer within audition to another frequency pair. In an interesting asymmetry, crossmodal learning transferred to all visual tasks but not to auditory tasks. Finally, in all conditions, learning to make TOJs for stimulus onsets did not transfer at all to discriminating temporal offsets. These data present a complex picture of timing processes.Conclusions/SignificanceThe lack of transfer between unimodal groups indicates no central supramodal timing process for this task; however, the audiovisual-to-visual transfer cannot be explained without some form of sensory interaction. We propose that auditory learning occurred in frequency-tuned processes in the periphery, precluding interactions with more central visual and audiovisual timing processes. Functionally the patterns of featural transfer suggest that perceptual learning of temporal order may be optimised to object-centered rather than viewer-centered constraints.
Highlights
Temporal processes are an essential aspect of perception and action
The first point is that robust learning occurred in all groups, with the improvement in temporal order judgment (TOJ) thresholds well described by the characteristic negative power function for all groups
They show that the improvement in temporal resolution for onset TOJs following unimodal training did not transfer at all to the other unimodal condition–neither from vision to audition, nor from audition to vision
Summary
Temporal processes are an essential aspect of perception and action. Towards the shorter end of these two extremes is a very critical time band that ranges from 10 s to 100 s of milliseconds [1]. This sub-second range, the focus of the current paper, is essential for many important sensory and perceptual tasks including speech perception, motion perception, motor coordination [2,3,4]. Sub-second timing is essential for coordinating crossmodal interactions and multisensory integration [5,6]. We use a perceptual learning paradigm to address this question
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