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. 2012 Mar 1;8(3):e1002405. doi: 10.1371/journal.pcbi.1002405

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Coen-Cagli et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.

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Modulation of simulated model responses when the surround is co-assigned (R_co-assign; e.g. with a large, homogeneous grating) relative to when it is not co-assigned (R_no-assign; e.g. with a grating smaller than the central RF). Percent surround modulation is computed as 100*(R_co-assign−R_no-assign)/R_no-assign. This quantity depends on RFs outputs only via and . Since appears in the denominator of Equation 3, the larger the the smaller the model response. We choose three representative values of (note that increases with larger center RF output). Surround modulation in the model can facilitate center responses for weak surrounds ( comparable with ), and gradually switch to suppression as surround strength (and therefore ) increases (relative to ). No surround modulation (dashed line) is observed e.g. with small stimuli or large, non-homogeneous stimuli for which center and surround RFs are not co-assigned.

Inline graphic — Modulation of simulated model responses when the surround is co-assigned (R_co-assign; e.g. with a large, homogeneous grating) relative to when it is not co-assigned (R_no-assign; e.g. with a grating smaller than the central RF). Percent surround modulation is computed as 100*(R_co-assign−R_no-assign)/R_no-assign. This quantity depends on RFs outputs only via and . Since appears in the denominator of Equation 3, the larger the the smaller the model response. We choose three representative values of (note that increases with larger center RF output). Surround modulation in the model can facilitate center responses for weak surrounds ( comparable with ), and gradually switch to suppression as surround strength (and therefore ) increases (relative to ). No surround modulation (dashed line) is observed e.g. with small stimuli or large, non-homogeneous stimuli for which center and surround RFs are not co-assigned.