Incremental grouping of image elements in vision

Abstract

One important task for the visual system is to group image elements that belong to an object and to segregate them from other objects and the background. We here present an incremental grouping theory (IGT) that addresses the role of object-based attention in perceptual grouping at a psychological level and, at the same time, outlines the mechanisms for grouping at the neurophysiological level. The IGT proposes that there are two processes for perceptual grouping. The first process is base grouping and relies on neurons that are tuned to feature conjunctions. Base grouping is fast and occurs in parallel across the visual scene, but not all possible feature conjunctions can be coded as base groupings. If there are no neurons tuned to the relevant feature conjunctions, a second process called incremental grouping comes into play. Incremental grouping is a time-consuming and capacity-limited process that requires the gradual spread of enhanced neuronal activity across the representation of an object in the visual cortex. The spread of enhanced neuronal activity corresponds to the labeling of image elements with object-based attention.

Object-based attention: A tutorial review

“…Perhaps the role of space in object-based selection is best illustrated in a recent study by Hollingworth, Maxcey-Richard, and Vecera (2012), who found interaction between space-and object-based attention within the same experimental paradigm. Consistent with the notion that there are linkages between lowerlevel spatial representations and higher-level spatially invariant representations at multiple levels of selection (Di Lollo, Enns, & Rensink, 2000;Hochstein & Ahissar, 2002;Roelfsema & Houtkamp, 2011;van der Velde & de Kamps, 2001), Hollingworth et al showed that whereas spatial attention forms a gradient across an attended object, the spread of this gradient is constrained by the boundaries of the object.…”

“…To date, the strongest physiological evidence supporting the within-group spread of attention has come from several recent studies by Roelfsema and colleagues (e.g., Roelfsema & Houtkamp, 2011;Wannig, Stanisor, & Roelfsema, 2011). In one experiment by Wannig et al (2011), monkeys were shown displays that consisted of two target bars and two distractor bars.…”

“…Valdes-Sosa et al (1998) showed their observers stimulus displays consisting of two sets of superimposed dots that differed either in both color and the direction of motion, thus Roelfsema and Houtkamp (2011). a Monkeys were trained to perform a curve-tracing task by making a saccade to the target upon a signal.…”

Object grouping based on real-world regularities facilitates perception by reducing competitive interactions in visual cortex

“…Distractors that can be grouped based on such low-level cues can be rejected at once rather than on an item-by-item basis, leading to enhanced target detection (16)(17)(18)(19)(20)(21)(22). For example, when distracters can be grouped by color, search performance depends on the number of distracter groups rather than on the number of individual distracters in each group (17).…”

Visual training improves perceptual grouping based on basic stimulus features

“…Effects of experience on grouping have been attributed to feedback from object representations that facilitate grouping at a low level of processing (Kimchi & Hadad, 2002). Proposed neural mechanisms of grouping emphasize integration across stimulus representations by means of modifying intrinsic and longrange connections (Kapadia, Ito, Gilbert, & Westheimer, 1995;Roelfsema & Houtkamp, 2011). Increased connection strength is a fundamental process underlying perceptual learning, suggesting that training on grouping tasks can enhance integration of stimulus components and thereby improve perceptual grouping.…”