Characteristics of perceptual grouping in rats

Parametric analysis was made of the characteristics by which proximity and alignment serve as cues for perceptual grouping in rats. Rats were initially conditioned to discriminate a series of horizontal lines from vertical lines. Following training, rats were presented with test stimuli that consisted of bistable arrays of disjunct dots. A grouping cue (greater proximity, greater alignment, or both) was randomly assigned to either the horizontal or vertical orientation. The effectiveness of the cues was based on behavioral responses to the cued orientation. Results indicated that proximity served as a cue for perceptual grouping. The effectiveness of the proximity cue was less for rats than found previously in humans and, unlike humans, diminished with increased stimulus scale. Rats did not respond to alignment cues when used in isolation, although alignment facilitated grouping when used in conjunction with proximity cues. Diminished effectiveness of grouping cues likely reduces object recognition abilities, particularly for complex visual stimuli.     

Preattentive visual search and perceptual grouping in schizophrenia

Differentiated retinal pigment epithelial (RPE) cells in vivo express basal levels of FGF-5, a secreted member of the FGF gene family. RPE cells proliferate in response to pathological events, resulting in a transient increase in FGF-5 gene expression. The goal of this study is to identify cis-acting sequences in the FGF-5 gene promoter which upregulate FGF-5 gene expression when differentiated RPE cells enter the cell cycle and proliferate. In vitro cultures of RPE cells were transfected with various FGF-5 promoter/luciferase deletion constructs, using methods specifically optimized for proliferating and differentiated RPE cells. A proximal promoter/enhancer whose activity is not cell-context dependent was identified between FGF-5 sequences -314 and +48. In addition, a silencer element (-1256/-883) was identified in the distal region which is active only in differentiated RPE cells. When tested in a heterologous system, the same element had silencer activity in differentiated cells. Two small regions in the distal FGF-5 gene promoter, -1195/-1173 and -984/-967 were able to specifically bind to nuclear proteins from differentiated RPE cells but not from proliferating RPE cells as evidenced by gel mobility shift assays. Therefore, FGF-5 gene expression in the RPE may be regulated by the formation of differentiation-specific complexes.     

Experience-dependent perceptual grouping and object-based attention.

Earlier studies have shown that attention can be directed to objects, defined on the basis of generic grouping principles, highly familiar shapes, or task instructions, rather than to contiguous regions of the visual field. The 4 experiments presented in this article extend these findings, showing that object attention benefits--shorter reaction times to features appearing on a single object--apply to recently viewed novel shapes. One experiment shows that object attention operates even when the visible fragments correspond to objects that violate standard completion heuristics. Other experiments show that experience-dependent object benefits can apply to fragments even without evidence of occlusion. These results attest to the flexible operation of the perceptual system, adapting as a function of experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the perceptual organization of speech.

A general account of auditory perceptual organization has developed in the past 2 decades. It relies on primitive devices akin to the Gestalt principles of organization to assign sensory elements to probable groupings and involves secondary schematic processes to confirm or to repair the possible organization. Although this conceptualization is intended to apply universally, the variety and arrangement of acoustic constituents of speech violate Gestalt principles at numerous junctures, cohering perceptually, nonetheless. Three experiments are reported on organization in phonetic perception, using sine wave synthesis to evade the Gesalt rules and the schematic processes alike. These findings falsify a general auditory account, showing that phonetic perceptual organization is achieved by specific sensitivity to the acoustic modulations characteristic of speech signals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Edge-region grouping in figure-ground organization and depth perception.

Edge-region grouping (ERG) is proposed as a unifying and previously unrecognized class of relational information that influences figure-ground organization and perceived depth across an edge. ERG occurs when the edge between two regions is differentially grouped with one region based on classic principles of similarity grouping. The ERG hypothesis predicts that the grouped side will tend to be perceived as the closer, figural region. Six experiments are reported that test the predictions of the ERG hypothesis for 6 similarity-based factors: common fate, blur similarity, color similarity, orientation similarity, proximity, and flicker synchrony. All 6 factors produce the predicted effects, although to different degrees. In a 7th experiment, the strengths of these figural/depth effects were found to correlate highly with the strength of explicit grouping ratings of the same visual displays. The relations of ERG to prior results in the literature are discussed, and possible reasons for ERG-based figural/depth effects are considered. We argue that grouping processes mediate at least some of the effects we report here, although ecological explanations are also likely to be relevant in the majority of cases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reconciling simplicity and likelihood principles in perceptual organization.

Two principles of perceptual organization have been proposed. The likelihood principle, following H. L. E von Helmholtz( 1910/1962), proposes that perceptual organization is chosen to correspond to the most likely distal layout. The simplicity principle, following Gestalt psychology, suggests that perceptual organization is chosen to be as simple as possible. The debate between these two views has been a central topic in the study of perceptual organization. Drawing on mathematical results in A. N. Kolmogorov's ( 1965 ) complexity theory, the author argues that simplicity and likelihood are not in competition, but are identical. Various implications for the theory of perceptual organization and psychology more generally are outlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and the perceptual organization of 3-D scenes.

In the current study, the authors investigated whether the ground dominance effect (the use of ground surface information for the perceptual organization of scenes) varied with age. In Experiment 1, a scene containing a ground, a ceiling, and 2 vertical posts was presented. The scene was either in its normal orientation or rotated to the side. In Experiment 2, a blue dot was attached to each post, with location varied from bottom to top of the posts. In Experiment 3, a scene similar to that in Experiment 1 was presented in different locations in visual field. Observers judged which of the 2 objects (posts in Experiments 1 and 3, blue dots in Experiment 2) appeared to be closer. The results indicated that both younger (mean age = 22 years) and older observers (mean age = 73 years) responded consistently with the ground dominance effect. However, the magnitude of the effect decreased for older observers. These results suggest a decreased use of ground surface information by older observers for the perceptual organization of scene layout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Figure-ground perceptual organization and learning by three-year-old children

The Self-defeating Personality Scale and a modified version of the Miller Social Intimacy Scale were given to 98 men (M(age) = 40.3) and 104 (M(age) = 40.0) women to validate criterion seven (rejects people who consistently treat him/her well) of the former. Both the correlation between the full scale scores and those for the Miller scale and the correlation between Miller scores and scores on criterion seven of the Self-defeating Scale were nonsignificant. Cronbach alpha was .51.     

The role of temporal cortical areas in perceptual organization

The visual areas of the temporal lobe of the primate are thought to be essential for the representation of visual objects. To examine the role of these areas in the visual awareness of a stimulus, we recorded the activity of single neurons in monkeys trained to report their percepts when viewing ambiguous stimuli. Visual ambiguity was induced by presenting incongruent images to the two eyes, a stimulation condition known to instigate binocular rivalry, during which one image is seen at a given time while the other is perceptually suppressed. Previous recordings in areas V1, V2, V4, and MT of monkeys experiencing binocular rivalry showed that only a small proportion of striate and early extrastriate neurons discharge exclusively when the driving stimulus is seen. In contrast, the activity of almost all neurons in the inferior temporal cortex and the visual areas of the cortex of superior temporal sulcus was found to be contingent upon the perceptual dominance of an effective visual stimulus. These areas thus appear to represent a stage of processing beyond the resolution of ambiguities--and thus beyond the processes of perceptual grouping and image segmentation--where neural activity reflects the brain's internal view of objects, rather than the effects of the retinal stimulus on cells encoding simple visual features or shape primitives.     

Reduced top-down influence in auditory perceptual organization in schizophrenia

Implants made form zirconium dioxide exhibit higher specific radionuclide activities of the uranium-radium and thorium series than metallic and aluminum implants. This study presents data on activity measurements performed on different samples of ZrO2 raw material (powder) and on the ceramic joint heads belonging to it to formulate a correlation between the specific radionuclide activities of the uranium-radium and thorium series in the raw material, the flux density of the alpha particle leaving the implant surface, and the annual dose of the tissue surrounding the implant. Based on this experimental study, an equation for defining the limits of the specific activities in raw material is proposed, taking into account the long-lived radionuclides (key nuclides) of the uranium-radium and thorium series weighted with their relative dose contributions from alpha emitters.     

Parallel and competitive processes in hierarchical analysis: Perceptual grouping and encoding of closure.

The role of perceptual grouping and the encoding of closure of local elements in the processing of hierarchical patterns was studied. Experiments 1 and 2 showed a global advantage over the local level for 2 tasks involving the discrimination of orientation and closure, but there was a local advantage for the closure discrimination task relative to the orientation discrimination task. Experiment 3 showed a local precedence effect for the closure discrimination task when local element grouping was weakened by embedding the stimuli from Experiment 1 in a background made up of cross patterns. Experiments 4A and 4B found that dissimilarity of closure between the local elements of hierarchical stimuli and the background figures could facilitate the grouping of closed local elements and enhanced the perception of global structure. Experiment 5 showed that the advantage for detecting the closure of local elements in hierarchical analysis also held under divided- and selective-attention conditions. Results are consistent with the idea that grouping between local elements takes place in parallel and competes with the computation of closure of local elements in determining the selection between global and local levels of hierarchical patterns for response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus configuration and context effects in perceptual organization in schizophrenia.

Two studies assessed perceptual organization in schizophrenia to determine (a) whether inpatient and outpatient groups with poor premorbid schizophrenia have comparable levels of perceptual organization deficit; and (b) whether the deficit could be eliminated by task manipulations. In Study 1, inpatients demonstrated clear evidence of a perceptual organization deficit, whereas outpatients performed similarly to the control groups. In Study 2, a performance pattern that operationally defined a perceptual organization deficit was eliminated by a task manipulation thought to aid in context processing. The perceptual organization deficit is most pronounced in actively symptomatic patients with poor premorbid schizophrenia, and the deficit reflects, in part, deficient top-down influences to basic perceptual processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Levels of perceptual organization and cognition: Conflicting evidence.

Low relations generally have been found between performance on perceptual and cognitive tasks. This experiment was designed to test the high relation reported by Krech & Calvin (see 28: 2250) between the ability to organize a group of dots into an articulated pattern and scores on the vocabulary section of the Wechsler Bellevue. The Krech measure yielded a higher relation than other perceptual measures to verbal test performance, although lower than that obtained by Krech & Calvin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time-course contingencies in perceptual organization and identification of fragmented object outlines.

To study the dynamic interplay between different component processes involved in the identification of fragmented object outlines, the authors used a discrete-identification paradigm in which the masked presentation duration of fragmented object outlines was repeatedly increased until correct naming occurred. Survival analysis was used to investigate whether and when different types of information—such as contour integration cues (proximity, collinearity, and fragment density), fragment properties (low vs. high curvature), stimulus complexity (global symmetry, number and saliency of the parts), and memory factors (natural vs. artifactual)—influenced the timing of identification. The results show that the importance of these different types of information can change over the time course of object identification, indicating so-called time-course contingencies. Most important, the straight segments of a contour played a larger role for complex outlines with high part saliency during early (bottom-up) grouping processes, whereas the curved segments of object outlines were more important during later (top-down) matching processes for simpler outlines with lower part saliency. This new insight can explain why different studies on shape-based object identification have produced seemingly contradictory results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Double dissociation and hierarchical organization of strategy switches and reversals in the rat PFC.

Prelimbic–infralimbic cortex (PL-IL) and orbitofrontal cortex (OFC) influence behavioral flexibility in the rat. The authors tested the effects of PL-IL or OFC infusion with the GABA agonist muscimol in the context of 2 flexible responding tasks: strategy switching and reversal. Muscimol infusion into PL-IL impaired retention of strategy switches but not reversals, whereas muscimol infusion into OFC impaired retention of reversals but not switches. However, whereas training in repeated reversals did not remove the requirement of PL-IL for switch retention (E. L. Rich & M. L. Shapiro, 2007), training in repeated switches did remove the requirement of OFC for reversal retention. Thus, activity during strategy switches was sufficient to initiate learning and remove the requirement of OFC in later reversals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An alternative hierarchical organization of the mental disorders of the DSM-IV.

With the approaching publication of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM), alternative organizations of the DSM (4th ed.; DSM-IV; American Psychiatric Association, 1994) categories have been proposed. This article compares several published alternative organizations to clinicians' organization of the DSM-IV categories. As demonstrations of their organization of DSM-IV categories, psychologists and psychiatrists sorted 66 DSM-IV diagnostic categories into groups of similar diagnoses and then made progressively larger and smaller groups of diagnoses or placed similar groups next to each other on a table. Hierarchical agglomerative data analysis of clinicians' individual sortings showed that clinicians retained many lower level DSM-IV categories (e.g., anxiety disorders, mood disorders), but not the higher level DSM-IV categories (e.g., Axis I vs. Axis II). Instead, at the highest hierarchical level, clinicians' categories resembled the structure of the first edition of the DSM (American Psychiatric Association, 1952), which followed clinicians' diagnostic decision-making scheme, dividing mental disorders into organic versus nonorganic and then psychotic versus neurotic disorders. At minimum, these data suggest a DSM organization that makes sense to clinicians. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bistability and hysteresis in the organization of apparent motion patterns.

In a paradigm for which 2 distinct patterns are perceived for the same stimulus, perceptual hysteresis (persistence of a percept despite parameter change to values favoring the alternative pattern) and temporal stability (persistence despite intrinsic propensities toward spontaneous change) are interdependent. Greater persistence during parameter change reduces temporal stability, slowing the rate of parameter change reduces hysteresis by increasing opportunity for spontaneous change, and increasing temporal stability (by enlarging the stimulus) increases hysteresis. Hysteresis results in the perception of parametrically disfavored patterns; a parameter can influence a percept without specifying it. The visual system thus exhibits time-dependent behavior analogous to dynamical behavior observed in other systems, both physical and biological, for which there is competition among alternative patterns that vary in relative stability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateralized perceptual organization deficits on the global-local task in schizotypal personality disorder.

Right and left hemisphere contributions to perceptual organization functions were examined using a divided-attention version of the global-local task in a sample of 21 unmedicated participants diagnosed with schizotypal personality disorder (SPD) and 20 controls. The SPD participants showed an abnormal global processing advantage. When the visual angle of the hierarchical stimuli was increased from 3° to 9°, the controls showed an increasing local processing advantage, but the SPD participants continued to show an abnormal global processing advantage. These findings suggest a local processing deficit on divided-attention versions of the global-local task in schizophrenia spectrum disorders. Female SPD participants, who had less severe interpersonal deficit symptoms, showed a more abnormal global processing advantage. Hemispheric and processing resource mechanisms that might explain these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phrasing cues and hierarchical organization in serial pattern learning by rats.

In Exp I, 42 female albino Sprague-Dawley rats received food quantities in a T-maze in a serial pattern. Ss learned under either no cue, temporal cue, place cue, and/or combined temporal-place cue conditions. In Exp II, 45 female albino Sprague-Dawley rats in the T-maze were trained in complex subpatterns with place cues or no cues. Exp I showed that phrasing facilitated pattern learning as long as phrasing cues were available but that Ss learned different things when different kinds of phrasing cues were used. Exp II showed that phrasing a pattern into formally complex rather than formally simple chunks produced poor learning. Overall findings demonstrate the rat's capacity to abstract and use higher-order rules in hierarchical serial patterns, especially when phrasing cues are available to facilitate the process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional persistence for features of hierarchical patterns.

Priming for perceptual wholes and parts was examined in 4 experiments involving patterns arranged in a spatial hierarchy (D. Navon, see record 1978-11488-001). Previous studies have demonstrated "level-specific priming" across successive trials for these patterns (L. C. Robertson et al, see record 80:40200; L. M. Ward, see record 69:02582), and studies in neuropsychology have shown an absence of this priming effect in patient groups with parietal damage (R. Rafal & L. M. Robertson, 1995). The present experiments demonstrate that level-specific priming is linked to the spatial frequency differences between global and local forms in hierarchical patterns. They also show that level-specific priming is present even when the stimulus as a whole changes location. The effects last for up to 3 sec without diminution and are not affected by changes in color, polarity, or contrast. These findings are discussed as they relate to spatial attention, object perception, and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)