How big is a Gabor patch, and why should we care?

We propose a two-parameter model for the perceived size (spatial extent) of a Gaussian-windowed, drifting sinusoidal luminance pattern (a Gabor patch) based on the simple assumption that perceived size is determined by detection threshold for the sinusoidal carrier. Psychophysical measures of perceived size vary with peak contrast, Gaussian standard deviation, and carrier spatial frequency in a manner predicted by the model. At suprathreshold peak contrasts Gabor perceived size is relatively unaffected by systemic noise but varies in a manner that is consistent with the influence of local contrast gain control. However, at and near threshold, systemic noise plays a major role in determining perceived size. The data and the model indicate that measures of contrast threshold using Gaussian-windowed stimuli (or any other nonflat contrast window) are determined not just by contrast response of the neurons activated by the stimulus but also by integration of that activation over a noisy, contrast-dependent extent of the stimulus in space and time. Thus, when we wish to measure precisely the influence of spatial and temporal integration on threshold, we cannot do so by combining contrast threshold measures with Gaussian-windowed stimuli.

[1]  Dennis Gabor,et al.  Theory of communication , 1946 .

[2]  James T. Todd,et al.  The effects of spatiotemporal integration on maximum displacement thresholds for the detection of coherent motion , 1995, Vision Research.

[3]  Frans A. J. Verstraten,et al.  Spatial summation and its interaction with the temporal integration mechanism in human motion perception , 1994, Vision Research.

[4]  H. Akaike.  A new look at the statistical model identification , 1974 .

[5]  J. Koenderink,et al.  Spatiotemporal integration in the detection of coherent motion , 1984, Vision Research.

[6]  A. Watson,et al.  The optimal motion stimulus , 1995, Vision Research.

[7]  A. B. Bonds.  Temporal dynamics of contrast gain in single cells of the cat striate cortex , 1991, Visual Neuroscience.

[8]  Robert Grover Brown,et al.  Introduction to random signal analysis and Kalman filtering , 1983 .

[9]  Hugh R. Wilson,et al.  Shifts in perceived size as a function of contrast and temporal modulation , 1983, Vision Research.

[10]  M. Silverman,et al.  Spatial frequency columns in primary visual cortex. , 1981, Science.

[11]  R A Young,et al.  The Gaussian derivative model for spatial vision: I. Retinal mechanisms. , 1988, Spatial vision.

[12]  S. Klein,et al.  Evidence against narrow-band spatial frequency channels in human vision: the detectability of frequency modulated gratings , 1975, Vision Research.

[13]  R. Young.  GAUSSIAN DERIVATIVE THEORY OF SPATIAL VISION: ANALYSIS OF CORTICAL CELL RECEPTIVE FIELD LINE-WEIGHTING PROFILES. , 1985 .

[14]  William H. Press,et al.  Numerical Recipes in C, 2nd Edition , 1992 .

[15]  Mark W. Cannon,et al.  Spatial interactions in apparent contrast: Inhibitory effects among grating patterns of different spatial frequencies, spatial positions and orientations , 1991, Vision Research.

[16]  J. Koenderink,et al.  The distribution of human motion detector properties in the monocular visual field , 1986, Vision Research.

[17]  D. Burr,et al.  Receptive field size of human motion detection units , 1987, Vision Research.

[18]  I. Ohzawa,et al.  Contrast gain control in the cat's visual system. , 1985, Journal of neurophysiology.

[19]  D. Field,et al.  The structure and symmetry of simple-cell receptive-field profiles in the cat’s visual cortex , 1986, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[20]  E. Switkes,et al.  Deoxyglucose analysis of retinotopic organization in primate striate cortex. , 1982, Science.

[21]  J. Daugman.  Spatial visual channels in the fourier plane , 1984, Vision Research.

[22]  D. Burr,et al.  Spatial summation properties of directionally selective mechanisms in human vision. , 1991, Journal of the Optical Society of America. A, Optics and image science.

[23]  E. Schwartz,et al.  On the mathematical structure of the visuotopic mapping of macaque striate cortex. , 1985, Science.

[24]  H. Wilson,et al.  Spatial frequency adaptation and contrast gain control , 1993, Vision Research.