Visual synchrony affects binding and segmentation in perception

The visual system analyses information by decomposing complex objects into simple components (visual features) that are widely distributed across the cortex(1,2). When several objects are present simultaneously in the visual field, a mechanism is required to group (bind) together visual features that belong 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 synchronizing the activity of their neural representations(3-6). If synchrony is important in binding, one would expect that binding and segmentation are facilitated by visual displays that are temporally manipulated to induce stimulus-dependent synchrony. Here we show that visual grouping is indeed facilitated when elements of one percept are presented at the same time as each other 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. Our results indicate that binding is due to a global mechanism of grouping caused by synchronous neural activation, and not to a local mechanism of motion computation.