Feature binding in zebrafish

The binding problem is the brainʹs fundamental challenge for advanced sensory processing: objects in the outside world possess multiple features, which must be bound into a cohesive perceptual representation. Although there is suggestive evidence that nonmammalian vertebrates (and possibly insects) may support it, this rudimentary form of sensory syntax is ascribed primarily to cortex or similarly complex avian structures. The experiments reported here provide evidence that a small vertebrate lacking cortex supports visual feature binding for social behaviour. Zebrafish, Danio rerio, displayed spontaneous preference for images of other zebrafish in which the visual attributes of form and motion were paired in a meaningful fashion, while each attribute in isolation was rendered ineffective as a cue for discrimination. The ability to conjoin the two features was robust and remarkably flexible. These results challenge the notion that feature binding may require cortical structures and demonstrate that the nervous system of small vertebrates can afford unexpectedly complex computations.