Psychophysical studies of contour detection (Kovács et al., 1996, Nafziger et al., 1998) indicate that the effective range of surround interactions scale inversely with stimulus density. We present a model based on psychophysical data which suggest that the size of the extra-classical receptive field (CRF) is dynamically modulated by stimulus context. Stimulus density acts to modulate the effective range of long-distance facilitatory connections: high stimulus densities narrow the effective range of the connection field, low densities enlarge the effective surround. Summed facilitatory inputs modulate the gain of the CRF. Simulations match the psychophysical results suggesting that a dynamic receptive field mechanism may underlie the inverse scaling of contour integration with stimulus density.

Keywords: Density normalization; Contour integration; Dynamic receptive fields