Combining 1-D components to extract pattern information: It is about more than component similarity

Abstract

At least under some conditions, plaid stimuli are processed by combining information first extracted in orientation and scale-selective channels. The rules that govern this combination across channels are only partially understood. Although the available data suggests that only components having similar spatial frequency and contrast are combined, the extent to which this holds has not been firmly established. To address this question, we measured, in human subjects, the short-latency reflexive vergence eye movements induced by stereo plaids in which spatial frequency and contrast of the components are independently varied. We found that, although similarity in component spatial frequency and contrast matter, they interact in a nonseparable way. One way in which this relationship might arise is if the internal estimate of contrast is not a faithful representation of stimulus contrast but is instead spatial frequency–dependent (with higher spatial frequencies being boosted). We propose that such weighting might have been put in place by a mechanism that, in an effort of achieve contrast constancy and/or coding efficiency, regulates the gain of detectors in early visual cortex to equalize their long-term average response to natural images.

Weighted summation and contrast normalization account for short-latency disparity vergence responses to white noise stimuli in humans

“…C 50 and m are the last two (seventh and eighth) free parameters of the model. For pure sine wave gratings, Equation 3 simplifies to which is a well-known Naka–Rushton equation ( Naka & Rushton, 1966 ), successfully used to describe DVR contrast dependencies to pure sine wave stimuli in the past ( Quaia, Optican, & Cumming, 2017 ; Rambold et al., 2010 ; Sheliga, FitzGibbon, et al., 2006 ). C 50 and m are, therefore, the Naka–Rushton semi-saturation contrast and power term, respectively.…”