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Contextual influences on visual processing
Tom Albright
Salk Institute
The visual image formed on the retina represents an amalgam of visual
scene properties, including the reflectances of surfaces, their
relative positions, and the type of illumination. The challenge
facing the visual system is to extract the "meaning" of the image by
decomposing it into its environmental causes. For each local region
of the image, that extraction of meaning is only possible if
information from other regions is taken into account. Of particular
importance is a set of image cues revealing surface occlusion and/or
lighting conditions. These information rich cues direct the
perceptual interpretation of other more ambiguous image regions. This
context-dependent transformation from image to perception has profound
- but frequently under-appreciated - implications for
neurophysiological studies of visual processing: To demonstrate that
neuronal responses are correlated with perception of visual scene
properties, rather than visual image features, neuronal sensitivity
must be assessed in varied contexts that differentially influence
perceptual interpretation. We review a number of recent studies that
have used this context-based approach to explore the neuronal bases of
visual scene perception.