Top-Down Facilitation of Visual Object Recognition

Cortical processing required for object recognition is traditionally thought to be propagating serially along a hierarchy of visual areas that analyze increasingly complex information. Recent efforts gradually promote the involvement of top-down facilitation in cortical functions, but how such processing is initiated remains a puzzle. A specific mechanism for the activation of top-down facilitation during visual object recognition is described in this chapter. This mechanism is triggered by the rapid projection of a partially analyzed version of the input image (that is, a blurred image) from early visual areas directly to the prefrontal cortex. As a result, the information that is activated in the prefrontal cortex is back-projected to “object-related” regions in the temporal cortex to produce expectations about the most likely interpretation of the input image. This top-down process facilitates recognition by substantially limiting the number of object representations that need to be considered. The relation between the top-down processes that facilitate recognition and the top-down processes that exert attentional influence is discussed in the chapter.