Serial versus parallel processing in mid-level vision: filling-in the details of spatial interpolation

The relationship between boundary completion and surface filling-in, two core mechanisms of mid-level vision, remains unclear. Here, we integrate recent empirical findings to shine new light onto the neural mechanisms of boundary completion and surface filling-in as well as their relation to each other. Specifically, we discuss several psychophysical and neurophysiological studies that, when taken together, support a model where object boundaries and visual surfaces are interpolated in parallel, with one process impacting the other. We suggest that visual boundary completion and surface filling-in are two interacting processes that are supported by neural processes that are distributed throughout several areas of the early visual system.