d V1 neuronal responses were studied by using two-photon imaging in awake monkeys  Visual objects contain rich local high-order patterns such as curvature, corners, and junctions. In the standard hierarchical model of visual object recognition, V1 neurons were commonly assumed to code local orientation components of those high-order patterns. Here, by using two-photon imaging in awake macaques and systematically characterizing V1 neuronal responses to an extensive set of stimuli, we found a large percentage of neurons in the V1 superficial layer responded more strongly to complex patterns, such as corners, junctions, and curvature, than to their oriented line or edge components. Our results suggest that those individual V1 neurons could play the role in detecting local high-order visual patterns in the early stage of object recognition hierarchy.
Recent work using two-photon imaging in the monkey REF started closing this gap by systematically investigating response properties of V1 neurons to an array of complex stimuli and found, for instance, that about half of the neurons in V1 are selective to complex patterns such as curvature, corners and junctions rather than just oriented line segments.
Complex Pattern Selectivity in Macaque Primary Visual Cortex Revealed by Large-Scale Two-Photon Imaging
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