Abstract
An important aspect of visual object recognition is the ability to perceive object shape. Two basic components of complex shapes are straight and curved contours. A large body of evidence suggests a modular hierarchy for shape representation progressing from simple and complex orientation in early areas V1 and V2, to increasingly complex stages of curvature representation in V4, TEO, and TE. Here, we reinforce and extend the concept of modular representation. Using intrinsic signal optical imaging in Macaque area V4, we find sub-millimeter sized modules for curvature representation that are organized from low to high curvatures as well as domains with complex curvature preference. We propose a possible 'curvature hypercolumn' within V4. In combination with previous studies, we suggest that the key emergent functions at each stage of cortical processing are represented in systematic, modular maps.
Highlights
Recognizing the shapes of objects requires information about local contour features, such as orientation and curvature
The encoding of contour orientation in the visual system begins in primary visual cortex (V1) with neurons selective for the orientation of visual contours, and, in the second visual area (V2), with neurons selective for cue-invariant contour orientation
We investigate whether there are functional domains representing contour curvature in area V4 of macaque monkey visual cortex, an important intermediate stage of shape encoding
Summary
Recognizing the shapes of objects requires information about local contour features, such as orientation and curvature. The encoding of contour orientation in the visual system begins in primary visual cortex (V1) with neurons selective for the orientation of visual contours, and, in the second visual area (V2), with neurons selective for cue-invariant contour orientation (that is, independent of whether contours are defined by luminance, motion, color, or depth cues). These two functions are first embodied in the ‘orientation domain’ in V1 [1,2,3] and the ‘higher order orientation domain’ in V2 [4,5]. It is unknown whether such neuronal responses are organized in any way akin to orientation maps in V1 and V2
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