Visual synchrony a ects binding and segmentation in perception

The visual system analyses information by decomposing complex objects into simple components (visual features) widely distributed across the cortex [1, 2] When several objects are simultaneously present in the visual eld, a mechanism is required to group (bind) together visual features belonging to each object and to separate (segment) them from features of other objects. An attractive scheme for binding visual features into a coherent percept consists of synchronising the activity of their neural representations [3, 4, 5, 6]. If synchrony plays a major role in binding, one should expect that grouping and segmentation are facilitated in visual displays that induce stimulus dependent synchrony by temporal manipulations. Here we show that visual grouping is indeed facilitated when elements of one percept are presented simultaneously and are temporally separated (on a scale below the integration time of the visual system [7]) from elements of another percept or from background elements. The experimental results indicate that the e ect is due to a global mechanism of grouping caused by synchronous neural activation and not to a local mechanism of motion computation.