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S. J. M. Rainville, W. L. Makous; The spatial tuning of perceived temporal synchrony. Journal of Vision 2001;1(3):153. doi: 10.1167/1.3.153.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Evidence that temporal synchrony promotes texture segregation even in the absence of spatial cues [e.g. Lee & Blake, 1999, Science, 284, 1165–1168] suggests that synchrony detection is key in solving the binding problem. However, it remains unknown whether the ability to detect synchrony depends on the spatial properties of these temporally correlated events. In the present study, we measured the spatial, orientation, and spatial-frequency tuning of visual mechanisms sensitive to temporal synchrony. Methods: We modulated the spatial phase of two Gabor microelements over time using filtered random noise with 9.4-Hz peak frequency and 2.6-octave bandwidth, and asked observers to judge their synchrony. We manipulated the level of synchrony between Gabors by partially phase-randomizing the temporal signal driving one of the two microelements. We defined threshold as the synchrony level corresponding to 75%-correct performance in a 2AFC task and measured performance for Gabors that differed either in their relative spatial positions, orientations, or spatial frequencies. Results: Spatial separation from 2 to 12 deg of arc had little effect on synchrony thresholds. However, thresholds increased significantly with differences in orientation and spatial frequency; orientation tuning was bandpass but broad (∼120 degrees) whereas spatial-frequency tuning was comparatively narrow (∼2 octaves). Conclusions: Visual mechanisms mediating synchrony perception are not tuned for space, somewhat tuned for orientation, and highly tuned for spatial frequency. Therefore, synchrony perception cannot be described independently from the spatial properties of temporally-correlated features. This selectivity is incompatible with current notions that the binding problem is solved via the non-specific detection of synchronous visual events.
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