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The Journal of Neuroscience, November 5, 2003, 23(31):9968-9980

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Behavioral/Systems/Cognitive
How Selective Are V1 Cells for Pop-Out Stimuli?

Jay Hegdé^1,2 and Daniel J. Felleman¹

¹Department of Neurobiology and Anatomy, University of Texas Medical School, Houston, Texas 77030, and ²Vision Center Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037

Many neurons in visual area V1 respond better to a pop-out stimulus, such as a single vertical bar among many horizontal bars, than to a homogeneous stimulus, such as a stimulus with all vertical bars. Many studies have suggested such cells represent neural correlates of pop-out, or more generally figure-ground segregation. However, preference for pop-out stimuli over homogeneous stimuli could also arise from a nonspecific selectivity for feature discontinuities between the target and the background, without any specificity for pop-out per se. To distinguish between these two confounding scenarios, we compared the responses of V1 neurons to pop-out stimuli with the responses to "conjunction-target" stimuli, which have more complex feature discontinuities between the target and the surround, as in a stimulus with a blue vertical bar among blue horizontal bars and yellow vertical bars. The target in conjunction-target stimuli does not pop out, which we psychophysically verified. V1 cells in general responded similarly to pop-out and conjunction-target stimuli, and only a small minority of cells (2% by one measure) distinguished the pop-out and conjunction-target stimuli from each other and from homogeneous stimuli. Nevertheless, the responses of approximately 50% of the cells were significantly modulated across all center-surround stimuli, indicating that V1 cells can convey information about the feature discontinuities between the center and the surround as part of a network of neurons, although individual cells by themselves fail to explicitly represent pop-out. In light of our results, unambiguous pop-out selectivity at the level of individual cells remains to be demonstrated in V1 or elsewhere in the visual cortex.

Key words: binding; center-surround summation; contextual modulation; feature integration; figure-ground segregation; serial search; striate cortex; surround modulation; visual search

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Received May 25, 2003; revised September 8, 2003; accepted September 11, 2003.

This article has been cited by other articles:

				M. A. Smith, R. C. Kelly, and T. S. Lee Dynamics of Response to Perceptual Pop-Out Stimuli in Macaque V1 J Neurophysiol, December 1, 2007; 98(6): 3436 - 3449. [Abstract] [Full Text] [PDF]

				M. J. van der Smagt, C. Wehrhahn, and T. D. Albright Contextual Masking of Oriented Lines: Interactions Between Surface Segmentation Cues J Neurophysiol, July 1, 2005; 94(1): 576 - 589. [Abstract] [Full Text] [PDF]

				C. Constantinidis and M. A. Steinmetz Posterior Parietal Cortex Automatically Encodes the Location of Salient Stimuli J. Neurosci., January 5, 2005; 25(1): 233 - 238. [Abstract] [Full Text] [PDF]

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