The binding problem has been discussed mainly in visual perception. If the binding in perception is carried out sequentially by selective attention, however, visual short-term memory (VSTM) faces the binding problem to recognize multiple objects simultaneously. Despite some theoretical accounts and empirical data for maintenance of multiple feature-bound objects, recent studies directly testing the binding in VSTM suggest that the capacity of feature-bound objects may be highly limited, consistent with an idea that binding is sequential even in VSTM. Binding in perception and VSTM may share a common mechanism operating on feature maps at lower- and higher-level visual areas, respectively.
Temporal synchrony is a critical cue for binding attributes processed by separate sensory channels, but it remains controversial how the brain computes synchrony across different attributes. Here we describe our hypothesis, time marker theory, which states that cross-attribute synchrony is not based on simultaneous completion of attribute processing, but on the comparison of salient features (time markers) extracted from sensory signals evoked by the stimulus. This hypothesis was originally proposed to account for an anomaly of visual attribute binding, color-motion asynchrony, and is being developed to explain cross-attribute temporal synchrony in general, including cross-modality judgments.