Information processing: A solution to the binding problem?

It is now widely accepted that the brain processes sensory information in a distributed, hierarchical fashion, even if the actual hierarchies are ambiguous at present [1,2]. Within hierarchies, such as that of the visual system [3] (Fig. 1), different aspects of the incoming sensory information — such as colour, texture, shape, motion and so on — are processed separately and in parallel [1]. At some stage, the spatially segregated representations of various aspects of the visual field must be recombined — ‘bound’ together — to form a unified perception of the visual world. How the brain solves this ‘binding-problem’ has puzzled and intrigued physiologists, psychologists and theoreticians for decades.