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CNBC researchers demonstrate the interactive nature of perceptual processing in early visual areas
Tai Sing Photo
Tai Sing Lee
CNBC Faculty Webpage

In a recent article in the June issue of Nature Neuroscience "Neural activity in early visual cortex reflects behavioral experience and higher-order perceptual saliency", CNBC faculty member Tai Sing Lee demonstrated that the neurons in the primary visual cortex (V1) and the secondary visual cortex (V2) are not simply static filters for detecting elementary features in a visual scene, but are sensitive to a variety of higher level contextual factors, for example, the inference of 3-dimensional shapes and the behavioral experience of the animals. These findings demonstrate that the early visual area is more dynamic and plastic than previously thought, and that it participates in many levels of visual processing using the recurrent feedforward and feedback connections among the different areas in the brain. This study provides strong evidence in support of the interactive nature of visual computation.

 

Fig. 1a Fig. 1b

V2 neurons, when their receptive fields are placed at the center display element, are found to be sensitive to the the difference in the surrounding context if the display elements are defined by 3-dimensional shape from shading stimuli (Fig. 1a), but not when these elements are 2D flat patterns (Fig. 1b). V1 neurons become sensitive to the surrounding shape context only after the monkeys have utilized the stimuli in their behaviors. In Fig. 1c, the difference in V1 neurons' long-latency response to the pop-out condition, in which the center element is different from the surround elements, and the uniform condition, in which the center element is the same as the surround elements corresponds to a neural correlate of the pop-out perception. The data suggest that V2 might have explicit machinery for computing and representing 3D information, and the sensitivity to 3D context in V1 is due to feedback.

 


Fig. C

Neural activity in early visual cortex reflects behavioral experience and higher-order perceptual saliency. Tai Sing Lee, Cindy F. Yang, Richard D. Romero, and David Mumford. Nature Neuroscience, 5(6), 589-597, 2002.