Reentrant Processing Research Articles

Object substitution without reentry?

G. Francis and F. Hermens (2002) used computer simulations to claim that many current models of metacontrast masking can account for the findings of V. Di Lollo, J. T. Enns, and R. A. Rensink (2000). They also claimed that notions of reentrant processing are not necessary because all of V. Di Lollo et al. 's data can be explained by feed-forward models. The authors show that G. Francis and F. Hermens's claims are vitiated by inappropriate modeling of attention and by ignoring important aspects of V. Di Lollo et al. 's results.

Gestalt grouping and common onset masking.

A four-dot mask that surrounds and is presented simultaneously with a briefly presented target will reduce a person's ability to identity that target if the mask persists beyond target offset and attention is divided (Enns & Di Lollo, 1997, 2000). This masking effect, referred to as common onset masking, reflects reentrant processing in the visual system and can best be explained with a theory of object substitution (Di Lollo, Enns, & Rensink, 2000). In the present experiments, we investigated whether Gestalt grouping variables would influence the strength of common onset masking. The results indicated that (1) masking was impervious to grouping by form, similarity of color, position, luminance polarity, and common region and (2) masking increased with the number of elements in the masking display.

Comment on "Competition for consciousness among visual events: The psychophysics of reentrant visual processes" (Di Lollo, Enns & Rensink, 2000).

V. Di Lolo, J. T. Enns, and R. A. Rensink (2000) reported properties of masking that they claimed were inconsistent with all current models. The current authors show, through computer simulation, that many current models can account for V. Di Lollo et al.'s (2000) data. Although V. Di Lollo et al. (2000) argued that their data could be accounted for only with models that incorporate reentrant processing, the current authors show that reentrant processing is not necessary.

Performance evaluation of re-entrant lines with multi-class jobs and multi-server workstations

An approximation method is proposed for estimating the performance measures of re-entrant lines with multiserver workstations based on the Mean Value Analysis (MVA) technique. The system of interest can be found in the semiconductor wafer fabrication line in which several circuit types are manufactured through re-entrant processes at both the single-job and the batch workstations. Each workstation may have several identical machines. Multi-class jobs are assumed to be processed in a predetermined routing, in which some processes may utilize the same workstation several times in the re-entrant fashion. The performance measures of interest are the steady-state average of the cycle time of each job class, the queue length of each buffer, and the throughput of the system. The system may not be modelled by a product form queueing network due to the inclusion of batch machines, multi-class jobs with different processing times, and multi-server workstations. Thus, a methodology is proposed for analysing such a reentrant line approximately using the iterative procedures based upon the MVA and some heuristic adjustments. Results of numerical tests are provided to show the performance of the proposed approach against the simulation results.

Asymmetric object substitution masking.

Object substitution masking occurs when a lateral mask persists beyond the duration of a target, reflecting reentrant processes in vision (V. Di Lollo, J. Enns, & R. Rensink, 2000). The authors studied whether substitution masking is location specific and whether it is symmetric around the target. A brief circular display of letters was presented along with a mask that designated the target. The mask was centered on the target or 1.1 degrees to the central or to the peripheral side. Substitution masking was found even when the target and the mask were at different locations. It was asymmetric and stronger when the mask was to the peripheral side of the target than to the central side. Asymmetric substitution was observed using various masks. It could not be explained by retina acuity gradients and was not attenuated by focused attention. The authors propose that target selection triggers an asymmetric inhibitory surround that is stronger toward the central side of the target.

Modelling, control and simulation of an IC wafer fabrication system: A generalized stochastic coloured timed Petri Net approach

This study presents a generalized stochastic coloured timed Petri net(GSCTPN) to model an IC wafer fabrication system. According to the GSCTPN, it models the dynamic behaviours of the IC fabrication system, such as loading, reentrant processing, unloading and machine failure. Furthermore, modular and synthesis techniques are used to construct a large and complex system model. The two major sub-models are the Process-Flow Model and the Transportation Model. The Transportation Model incorporates a simple motion-planning rule and a collision avoidance strategy to solve the variable speed and traffic jam problems of vehicles. This work also describes a simulation based performance analysis and schedule adjustment. To demonstrate the promise of the proposed work, this study makes actual Taiwanese IC wafer fabrication systems the target plant layout for implementation.

Competition for consciousness among visual events: the psychophysics of reentrant visual processes.

Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments that defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors such as set size. This later process is called masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation and the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides a more comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions.

Emotion, motivation, and anxiety: brain mechanisms and psychophysiology

The organization of response systems in emotion is founded on two basic motive systems, appetitive and defensive. The subcortical and deep cortical structures that determine primary motivated behavior are similar across mammalian species. Animal research has illuminated these neural systems and defined their reflex outputs. Although motivated behavior is more complex and varied in humans, the simpler underlying response patterns persist in affective expression. These basic phenomena are elucidated here in the context of affective perception. Thus, the research examines human beings watching uniquely human stimuli—primarily picture media (but also words and sounds) that prompt emotional arousal—showing how the underlying motivational structure is apparent in the organization of visceral and behavioral responses, in the priming of simple reflexes, and in the reentrant processing of these symbolic representations in the sensory cortex. Implications of the work for understanding pathological emotional states are discussed, emphasizing research on psychopathy and the anxiety disorders.

Nested reentrant and recurrent computation in early vision: a Bayesian neuromorphic model applied to hyperacuity

Hyperacuity is demonstrated in a neuromorphic model of the early visual system. The model incorporates Bayesian principles which are embodied in the dynamics of reentrant and recurrent feedback processes. Each retinotopically mapped area in the model represents a transformation of data from the visual field. Sensory information propagates in a bottom-up direction from one area to the next, while information based on Bayesian priors propagates in a top-down direction through reentrant connections. The 'bottom-up' and 'top-down' information maintain a separate existence in distinct layers of the model, but they interact through local connections within each area. Transformations between one area and the next are defined by the reentrant synaptic connections between areas, while local prior probability maps are defined by local recurrent connections within layers. The representation of hyperacuity is accomplished using a model of functional multiplicity: the large ratio of neurons in striate cortex compared with the number of afferent fibers projecting from the lateral geniculate nucleus. High functional multiplicity, in conjunction with hierarchical reentrant processing, allows the model to represent a fine-grained restoration of the line structure of visual input.

Integration of distributed cortical systems by reentry: a computer simulation of interactive functionally segregated visual areas

A computer model based on visual cortex has been constructed to analyze how the operations of multiple, functionally segregated cortical areas can be coordinated and integrated to yield a unified perceptual response. We propose that cortical integration arises through the process of reentry--the ongoing, parallel, recursive signaling between separate maps along ordered anatomical connections. To test the efficacy of this reentrant cortical integration (RCI) model, we have carried out detailed computer simulations of 3 interconnected cortical areas in the striate and extrastriate cortex of the macaque. The simulated networks contained a total of over 222,000 units and 8.5 million connections. The 3 modeled areas, called VOR, VOC, and VMO, incorporate major anatomical and physiological properties of cortical areas V1, V3, and V5 but are vastly simplified compared with monkey visual cortex. Simulated area VOR contains both orientation and directionally selective units; simulated area VMO discriminates the direction of motion of arbitrarily oriented objects; and simulated area VOC responds to both luminance and occlusion boundaries in the stimulus. Area VOC is able to respond to illusory contours (Kanizsa, 1979) by means of the same neural architecture used for the discrimination of occlusion boundaries. This architecture also generates responses to structure-from-motion by virtue of reentrant connections from VMO to VOC. The responses of the simulated networks to these illusions are consistent with the perceptual responses of humans and other species presented with these stimuli. The networks also respond in a consistent manner to a novel illusion that combines illusory contours and structure-from-motion. The response synthesized to this combined illusion provides a strong argument supporting the need for a recursive reentrant process in the cortex. Functional integration of the simulated areas in the RCI model were found to depend upon the combined action of 3 reentrant processes: (1) conflicting responses among segregated areas are competitively eliminated, (2) outputs of each area are used by other areas in their own operations, and (3) outputs of an area are "reentered" back to itself (through lower areas) and can thus be used iteratively to synthesize responses to complex or illusory stimuli. Transection of the reentrant connections selectively abolished these integrative processes and led to failure of figural synthesis. The proposed model of reentry suggests a basis for understanding how multiple visual areas as well as other cortical areas may be integrated within a distributed system.