Climbing the cortical ladder from sensation to perception

A recent study using displays that are ambiguous for motion direction demonstrates that the current perceptual interpretation of such a stimulus is encoded in the highest areas of visual cortex whereas earlier areas encode only its sensory properties. This finding implies that cortical processing pathways perform a transition from a sensory representation to a representation that emphasizes the input's perceptual interpretation and ultimately the organism's behavioral state.The visual system of primates is highly structured, containing several dozen distinct areas. These areas are organized into a hierarchical system for the analysis of sensory information in which processing pathways, that is, chains of serially connected areas, can be identified. One of the central questions of systems neuroscience is how the task of analyzing the visual input is divided amongst the members of such cortical pathways [1]. Recent findings by Williams et al.[2] support the hypothesis that a visual pathway is more than a series of sensory processing steps, and in fact represents a gradient from a sensory-centered representation in the early cortical areas to an internal representation of the visual world in higher cortical areas that reflects the organism's current behavioral state and its perceptual interpretation of the sensory input.