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Kazushi Maruya, Alex Holcombe, Shin'ya Nishida; A high temporal resolution and long-range mechanism that identifies which motion directions occur at the same time. Journal of Vision 2011;11(11):1216. doi: 10.1167/11.11.1216.
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Synchrony provides critical information for perceiving spatiotemporal structures from parallel inputs. Temporal resolution of binding by synchrony can be assessed by eliciting judgments of which features occur at the same time across two changing stimuli in separate locations. Temporal resolution is higher within a single sensory attribute than between two attributes (Holcombe & Cavanagh, 2001; Fujisaki & Nishida, 2010). It remains obscure whether characteristics of within-attribute binding are similar for various attributes. Here we show motion binding is distinct from others. Our stimulus consisted of two elements, each an oscillating 1/f-noise carrier windowed by a stationary Gaussian. We measured the threshold oscillation rate beyond which the observer could not tell whether the oscillations of the elements were in a specific relative phase (e.g., up at the same time as up, alternating with down-down) or in the opposite phase (up-down alternating with down-up). RESULTS. (i) High temporal resolution: Thresholds for motion were ∼15 Hz, significantly better than luminance or orientation binding measured at the same eccentricities. (ii) Remote interaction: Threshold rates remained high even at the longest inter-element separation tested (40 dva), while luminance and orientation thresholds dropped significantly. (iii) Path dependency: Threshold rates for motion remained high for various combinations of oscillation axes. However, an exception occurred when the oscillation axes formed a virtual T-junction, e.g., one element oscillated horizontally (0 deg), and the other vertically (90 deg), with the two aligned horizontally or vertically. Yet even with the same 90-deg difference, the combination of +45 deg and −45 deg, arranged in a virtual L-junction, showed a high threshold rate. Motion processing apparently has a special long-range mechanism, possibly to sense temporal relationships among potentially connectable local motion signals. This overturns previous suppositions (Holcombe, 2009; Nishida & Johnston, 2010) of how the architecture of the visual system limits temporal resolution.
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