Our results indicate that spatial pooling is both non-linear and configuration specific. The idea that the whole is different from the sum of its parts (non-linearity) and that the visual system organizes parts into wholes (configuration) is a central idea in Gestalt theory. The facilitation effect can be found only when the three Gabor patches share the same orientation and spatial frequency as predicated by the Gestalt grouping rule. Similarity, proximity and smoothness effects have been demonstrated recently [2,9,15]. These rules seem to be implemented by long range spatial interactions.
Spatial interaction effects are functions of distance, contrast and similarity of test-mask and spatial configuration. Each cell therefore receives a network of inhibitory and excitatory connections to create a second stage of spatial filtering. Interaction effects may synchronize activity in the network to serve a grouping function [10,10]. Antagonistic connections in the network may result in an elongated second-stage interaction field which may underlie our ability to group lines and smooth curves.