Figure-ground mechanisms provide structure for selective attention

Abstract

Attention depends on figure-ground organization: figures draw attention, while shapes of the ground tend to be ignored. Recent research has demonstrated mechanisms of figure-ground organization in the visual cortex, but how they relate to the attention process remains unclear. Here we show that the influences of figure-ground organization and volitional (top-down) attention converge in single neurons of area V2. While assignment of border ownership was found for attended as well as for ignored figures, attentional modulation was stronger when the attended figure was located on the neuron's preferred side of border ownership. When the border between two overlapping figures was placed in the receptive field, responses depended on the side of attention, and enhancement was generally found on the neuron's preferred side of border ownership. This correlation suggests that the neural network that creates figure-ground organization also provides the interface for the topdown selection process.Perception tends to segregate visual images into figures and ground, and process the figure regions, but not the ground regions (Fig. 1). 1,2 Apparently, the system is able to group the visible borders at an early stage to configurations that are likely to be objects and process this information with priority. Objects can be selected by spatial filtering when they are separated ('spotlight of attention', Fig. 2a), but such a mechanism fails when objects are partially occluded by others as in everyday images. When trying to select the bottom square in Figure 2b for example, such a mechanism would select contours in the form of an L rather than a square. Observers generally perceive the square-not the L. Apparently, the visual system first subtracts the contours of the occluding object, to use only the remaining contours for further analysis, acknowledging that information is missing (Fig. 2c). Thus, an essential step in the interpretation of images is the correct assignment of the visible borders (contours, edges) to foreground regions. 3,4 Regions of occluded objects are bounded by two types of contour, those that are inherently related to the object (intrinsic contours), and those formed accidentally by interposition of another object (extrinsic contours). 3 Only the intrinsic contours should be processed together for shape recognition; extrinsic contours should be excluded. Single cell recordings from monkey visual cortex have shown that assignment of border ownership occurs at stages as early as areas V1 and V2. 5-7 Neurons in V2 are also influenced by top-down attention. 8-12 How these two processes are related is not clear. Is figure-ground organization the result of selective attention, or is it an independent process? If it is independent, as we shall argue, what is its role in the deployment of attention? Does it enable the attention process to select contours according to border ownership (interface hypothesis), or is attentional modulation determined merely by the distance of a contour from the focus of attentio...

Mechanisms of perceptual organization provide auto-zoom and auto-localization for attention to objects

“…The model presented here quantitatively reproduces the sideof-figure-dependent influence of attention in border ownership neurons (10) and it qualitatively reproduces reaction time effects of task-irrelevant perceptual objects (3,11). Important for its function are reciprocal connections between cells coding for the local features and those integrating them and inhibition between inconsistent representations.…”

“…Subsequently, matching the experimentally observed strength of attentional modulation of B cells (10) constrains the strength of the attention input. We find that the maximal value of the attentional input to grouping cells needs to be 7% of the direct excitatory input that a grouping cell receives from a figure of its optimal size.…”

“…How can attention, which is controlled by regions in the frontal and parietal cortex (1,2), access detailed visual features that are not available in those regions? Psychophysical (3-7) and neurophysiological (8)(9)(10) studies indicate that attentional selection operates on a structured representation of the visual input that is organized in terms of perceptual objects. We here propose that the neural circuitry that generates this perceptual organization also serves to shape the broad attentional feedback and to adapt it to individual perceptual objects.…”

Neural evidence for competition-mediated suppression in the perception of a single object

“…Some of these studies posit that attention is necessary for competition to occur (Zhang et al, 2011), while others posit that attention simply enhances suppression resulting from competition (Ling & Blake, 2012). Consistent with these findings regarding competition in binocular rivalry, research investigating figure-ground segregation has shown that attention directed towards two regions sharing a border can enhance the modulation of neural responses by figure-ground status (Craft et al, 2007;Poort et al, 2012;Qiu, Sugihara, & von der Heydt, 2007).…”

A dynamic neural field model of temporal order judgments.

“…Critically, there is robust behavioral and neural support for this property of the model suggesting that neural activation differs between figures and grounds. For example, Vecera and O'Reilly generated and tested a model to explain the increased salience of foreground figures relative to ground regions (see Vecera & O'Reilly, 1998, 2000; also see Kienker, Sejnowski, Hinton, & Schumacher, 1986;Sejnowski & Hinton, 1987; but see Peterson, 1999, andPeterson &Skow, 2008 Qiu, Sugihara, & von der Heydt, 2007). Therefore, it is reasonable to assume that the Seg input is asymmetrical between figures and grounds and can be a critical factor in generating consequences of figure-ground organization (e.g., prior entry and temporal extension effects).…”