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A Two-Stage Cascade Model of BOLD Responses in Human Visual Cortex

Figure 11

Natural images have relatively large amounts of second-order contrast.

(A) Simulation results. We prepared a collection of band-pass filtered natural image patches and phase-scrambled versions of these patches. We then quantified the amount of second-order contrast in each patch by computing the response of the SOC model to the patch (model parameters were set to the typical values found in V2). The median and interquartile range of responses are shown. For comparison we show results obtained when the second-order parameter c is set to 0. The SOC model but not the control model exhibits larger responses to the natural image patches. (B) Example patches. The natural image patch exhibits spatial variation in contrast, whereas its phase-scrambled counterpart is relatively homogeneous in contrast across space. Natural images were obtained from the McGill Colour Image Database [73].

Figure 11