Black' dominance measured with different stimulus ensembles in macaque primary visual cortex V1
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1
New York University , Center for Neural Science, United States
Most neurons in output layer 2/3 (not input layer 4c) of the primary visual cortex (V1) have stronger responses to ’black’ (negative contrast) than to ’white’ (positive contrast) when measured by reverse correlation with sparse noise (randomly positioned dark and bright spots against a gray background; Jones and Palmer 1987). The black-dominant response of monkey V1 neurons may serve as the neuronal substrate for human perception: in many perceptual tasks black is much more salient than white. Furthermore, the degree of the black dominance in V1 depends on the stimulus ensemble - the black dominance in layer 2/3 of V1 is much stronger when neuronal responses are measured with sparse noise than with Hartley subspace stimuli (a series of gratings at different orientations, spatial frequencies and spatial phases; Ringach et al 1997). Sparse and Hartley stimuli differ significantly in many ways. First, the individual stimulus size of the sparse noise is much smaller and therefore activates fewer V1 neurons simultaneously than that of the Hartley dense noise. Second, the dark and bright pixels of the sparse noise are present separately in time while those of the Hartley dense noise are shown simultaneously. Third, there are spatial correlations along the long axis of the Hartley stimuli that are not present in sparse noise. Which of these differences might contribute to the disparity in black dominance? We addressed this question by introducing a third stimulus ensemble - a binary checkerboard white noise (Reid et al 1997) - to measure the black-dominant responses in monkey V1. The binary white noise and Hartley dense noise share several properties in common: both activate a larger population of neurons than the sparse noise, and dark and bright pixels appear simultaneously under both conditions. However, unlike Hartley dense noise, neighboring pixels of binary white noise are uncorrelated. To make fair comparisons across different stimulus ensembles, only those neurons with significant responses (signal-to-noise ratio>1.5) to all three ensembles were included (n=32). Consistent with previous findings (Yeh et al 2009), black-dominant neurons largely outnumbered white-dominant neurons in layer 2/3 of V1 with all three stimulus ensembles (percentage of black-dominant neurons: 76~82%), while the numbers of black and white-dominant neurons were nearly equal in input layer 4c (percentage of black-dominant neurons: 40~60%). The degree of the black-dominant response was significantly stronger for binary white noise than for Hartley dense noise (p<0.02, Wilcoxon signed rank test). These results indicate that the degree of black dominance depends on the spatial structure of the stimulus ensemble. Acknowledgements: This work was supported by NIH-EY001472, NSF-0745253, the Robert Leet and Clara Guthrie Patterson Trust Postdoctoral Fellowship, and the Swartz Foundation.
Conference:
Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010.
Presentation Type:
Poster Presentation
Topic:
Poster session III
Citation:
Yeh
C,
Xing
D and
Shapley
R
(2010). Black' dominance measured with different stimulus ensembles in macaque primary visual cortex V1.
Front. Neurosci.
Conference Abstract:
Computational and Systems Neuroscience 2010.
doi: 10.3389/conf.fnins.2010.03.00315
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Received:
08 Mar 2010;
Published Online:
08 Mar 2010.
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Correspondence:
Chun-I Yeh, New York University, Center for Neural Science, New York, United States, ciy@cns.nyu.edu