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Lynnette Leone, Mark McCourt; Dissociation of Perception and Action in Audiovisual Multisensory Integration. Journal of Vision 2015;15(12):854. doi: https://doi.org/10.1167/15.12.854.
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© ARVO (1962-2015); The Authors (2016-present)
Early reports of audiovisual (AV) multisensory integration (MI) indicated that unisensory stimuli must evoke simultaneous physiological responses to produce decreases in reaction time (RT). The “temporal rule” states that MI depends on the temporal proximity of unisensory stimuli, the neural responses to which must fall within a temporal window of integration. Ecological validity demands that MI occur only for simultaneous events (which may give rise to non-simultaneous neural activations), and spurious neural response simultaneities unrelated to veridical multisensory occurrences must be rejected. Two experiments investigated the question of simultaneity in AV MI. Experiment 1 used an RT/race model paradigm to measure AV MI as a function of stimulus onset asynchrony (SOA: ±200 ms, 50 ms intervals) under fully dark-adapted conditions for visual (V) stimuli that were either rod- (scotopic 525 nm flashes; 511 ms mean RT) or cone-isolating (photopic 630 nm flashes; 356 ms mean RT). Auditory (A) stimulus (1000 Hz tone) intensity was constant. Despite the 155 ms slower mean RT to the scotopic versus photopic stimulus, facilitative AV MI in both conditions occurred exclusively at a 0 ms SOA. Thus, facilitative MI demands both physical and physiological simultaneity. Experiment 2 investigated the accuracy of simultaneity and temporal order judgments with these same stimuli. Facilitation of RT was not reflected in accurate judgments of AV stimulus simultaneity or temporal order (difference in average PSS = 74.79 ms and 40.08 ms, respectively). We consider the mechanisms by which the nervous system may take account of variations in neuronal response latency arising from changes in stimulus intensity to selectively integrate only those physiological simultaneities that arise from physical simultaneities. We discuss the possibility that this integration is predominantly for the purpose of taking action, that vision for perception may be more susceptible to temporal discrepancies.
Meeting abstract presented at VSS 2015
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