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PubMed1998

Identification of fragmented pictures in patients with brain damage.

Identification of fragmented pictures was investigated using line drawings (Snodgrass, Smith, Feenan, & Corwin, 1987) in 236 healthy participants and 43 patients with unilateral lesions of the right or left hemisphere. Perceptual closure (the integration of fragments into a meaningful perceptual whole) depended on the amount of physical visual information, the age of the patient, and the location of the lesion. Patients with right-side lesions showed more impairment than those with left-side lesions, confirming the importance of the right hemisphere in perceptual closure tasks. Right-hemisphere functions involved in perceptual closure, however, were not completely abolished, as performance improved with increasing visual information. The advantages of Snodgrass fragmented pictures as a neuropsychological test are discussed.

Journal Article↗
PubMed1982

Effect of presentation time and Gestalt principles of proximity, similarity, and closure on perceptual accuracy.

The present study investigated Gestalt principles of proximity, similarity and closure. 32 subjects reproduced distances between dots and lines. Two stimulus exposure times were used. Time was significant for proximity, similarity, and closure. Type of distance estimated was significant for proximity and closure and the interaction of time and type of distance was significant for similarity. Most accurate estimations were consistently found for fast exposure times, and internal distances were estimated more accurately than external distances.

Adult↗
PubMed1984

Eye-movement patterns in disabled readers at two age levels: a test of Bakker's balance model.

The eye-movement patterns of good and poor readers at two age levels during slide-presented reading, arithmetic and perceptual-closure tasks were compared. Older dyslexics were deficient in reading and arithmetic, but performed well on perceptual-closure tasks. Younger dyslexics were deficient on all tasks. Both younger good readers and older poor readers appeared to use a right-hemispheric reading strategy, while older dyslexics appeared to show a left-hemispheric approach. Younger dyslexics did not exhibit any strategy at all. Implications for Bakker's balance model of dyslexia and for subtypes research in dyslexia are discussed.

Age Factors↗
PubMed1993

The effect of contour closure on the rapid discrimination of two-dimensional shapes.

An outline drawing often serves as an excellent depiction of a visual scene. Somehow, our visual system can form two- and three-dimensional percepts solely from one-dimensional contour information. In mathematics, contour closure plays a key role in bridging this dimensional gap, however in perception the link between closure and shape is unclear. To better understand this relationship, we devised a set of visual search experiments in which subjects discriminate outline figures by means of their two-dimensional shape. By modulating the degree of closure of the outlines, we show that two-dimensional shape processing is rapid for closed stimuli but slow for open stimuli. We further show that search can be characterized as a smooth, monotonic function of the degree of closure, supporting the notion of a perceptual closure continuum.

Contrast Sensitivity↗
PubMed2002

Closure principle: relations across domains.

The present study examined a possible relationship between perceptual closure and social need for closure. These closure abilities were not correlated across domains of application.

Adolescent↗
PubMed1987

In search of closure: subjective contour illusions, Gestalt completion tests, and implications.

This study investigates the construct validity of perceptual closure tests (CTs), and isolates a common processing demand from the right-hemisphere. Sixty-seven patients with focal unilateral lesions (34 right side, 33 left side), and 80 control subjects participated. Multivariate analyses indicated that there was substantial age-related variance in all CTs, while sex was variably significant; CTs are not uniform in their discriminating ability, and hence factorially complex; and their specifically right hemisphere-sensitive dimension was subjective contour illusions, and interestingly unrelated to facial discrimination ability. The methodological and theoretical implications are discussed.

Brain Damage, Chronic↗
PubMed1997

Closure and acuity in pseudoisochromatic color tests.

While visual acuity was related to performance on several pseudoisochromatic color tests for 73 male college students, no evidence was found that perceptual closure also affected performance. No scores were correlated for the 69 undergraduate women.

Age Factors↗
PubMed2004

Facial closure: interrelationship with facial discrimination, other closure tests, and subjective contour illusions.

Findings from previous research have argued for the dissociation of two visual-perceptual tasks traditionally thought to be mediated by the nondominant hemisphere (i.e. perceptual closure and facial discrimination). This, primarily methodological, study examined the extent to which the facial closure measure (Mooney closure faces test) involves "closure" and/or facial discrimination. A factor analysis of six visual perceptual measures, carried out separately for left brain damaged (LBDs, n=33) and right brain damaged (RBDs, n=30) patients, resulted in two relatively independent factors (i.e. a closure factor and a facial discrimination factor), with the Mooney closure faces test loading on both. The mixed factorial structure did not aid the facial closure measure's sensitivity to right-sided brain disease. Moreover, age and education intercorrelated differently with the two factors. Results argue for the use of more discrete visual-perceptual measures when examining perceptual functioning and/or right hemisphere integrity, and imply the existence of at least two discrete cortical level visual-perceptual neural systems.

Adult↗
PubMed1994

A measure of closure.

In images of real visual scenes, contours are often fragmented by occlusion, shadows and low reflectance contrast. In order to infer shape from contour, the human visual system must selectively integrate fragments projecting from a common object while keeping fragments from different objects separate. In a previous paper we showed that contour closure has a strong influence on the speed of this process. In this paper we employ a visual search method to evaluate potential measures for the perceptual closure of fragmented shapes. We show that while certain intuitive measures are psychophysically inconsistent, a measure based on a sum of squares of the lengths of contour gaps is appropriate for both polygonal and smooth shapes in that response time can be expressed as a function of this measure. This L2 measure is shown to emphasize large gaps relative to small, and to embody a principle of perceptual regularity.

Discrimination, Psychological↗
PubMed1992

[Visual and motor functions in schizophrenic patients].

In the present work, visual and motor functions have been explored in 26 chronic schizophrenic patients, and 7 acute schizophrenic patients, compared with 26 normal controls, by means of the Bender-Gestalt Test. Parameters under consideration were: Form distortion, rotation, integration, perseveration, use of space, subtle motricity, score (global parameter), and time employed. As regards distortion and rotation there have been highly significant differences between chronic patients and control group. Among acute patients, it was observed that perseveration was also highly significant. Conversely, integration and use of space did not differ significantly among the three groups involved. The global score, resulting from all the above mentioned parameters showed important differences between both patient groups on the one hand, and control group on the other hand. Taking into account that patients were being administered neuroleptic drugs, it can safely be said, however, that the Bender-Gestalt Test allows to recognize alteration in perceptual closure consistent with a loss of the objective structure of perceived phenomena, in both chronic and acute patients.

Adult↗
PubMed1984

Evidence for differentiation of right hemisphere visual-perceptual functions.

Performance on tasks sensitive to right hemisphere dysfunction (facial discrimination and perceptual closure) are reported in eight patients with right hemisphere lesions. Patients demonstrated an apparent double dissociation of performance on the two measures. Site-by-task specificity for the closure task was strongly suggested. Implications for right hemisphere organization and underlying psychological processes are considered.

Adult↗
PubMed1980

Comparative study of factor structure of Raven's Coloured Progressive Matrices.

The Raven Coloured Progressive Matrices were administered on group or individual bases to children ranging in age from 4 yr. 9 mo. to 11 yr. 0 mo. (N = 728). Factor analysis yielded three factors: 1. Perceptual closure involving complex figures and patterns with heterogeneous inner structures, 2. Concrete and abstract reasoning, 3. Completion of homogeneous patterns and recognition of given elements. Factor matrix comparisons across age groups resulted in a mean similarity coefficient of .75. Comparisons of data with earlier analyses also resulted in high similarity. This supports the hypothesis of a three-factor structure rather than a four-factor solution or a simple dual classification into items which can be solved by perceptual processes and those which require conceptual solutions.

Child↗
PubMed2004

Kanizsa subjective figures capture visual spatial attention: evidence from electrophysiological and behavioral data.

Figural binding and attention are two important processes that help to perceive the outside world. Binding is necessary to link together the different features of single objects which are represented in a distributed fashion in the brain. Attention serves to focus onto a small subset of incoming information. It is still not clear how exactly these two mechanisms operate and interact. We performed two experiments employing illusory Kanizsa figures (KFs) to investigate the temporal order of figural binding and spatial attention. In a visual search task, subjects had to detect the presence of a KF among distractor stimuli. We found only a slight increase of reaction times when increasing the number of distractors, indicating that KFs popped out and drew the perceiver's attention. In a further event-related potential (ERP) study, we used displays of the search task as non-informative cue for a subsequent target choice-reaction task. Enhanced contralateral negative amplitudes (starting at about 230 ms) over ventral occipital areas were found for cue displays which included a KF. For target stimuli, faster reaction times and enhanced ipsilateral N1 amplitudes over occipito-parietal areas were observed for validly (target presentation inside a KF) as compared to invalidly cued targets (target presentation outside a KF). Furthermore, enhanced contralateral N1 amplitudes were found for invalidly cued targets. It might be that interactions between perceptual closure processing of the ventral pathway and spatial target processing of the dorsal pathway contributed to the present result. We conclude that KFs automatically capture spatial attention when used as visual cues.

Adult↗
PubMedDate not supplied

Age cohort differences in the ability to perform closure on degraded figures.

Young (17-26) and old (60-80) men and women performed a perceptual closure task for degraded line drawings under three conditions of prior picture knowledge (exact, similar, no prior knowledge) and two conditions of perceptual noise (contour or detail drawings) resulting in six levels of task difficulty. Young and old subjects took equal advantage prior knowledge conditions, however, old subjects required a greater percentage of picture and more time to make closure under all conditions when compared to young subjects. To test the perceptual slowing hypothesis, old subject performance was regressed on that of young across three levels of task difficulty. The slope of these regression equations supported the notion of a perceptual slowing hypothesis to explain age cohort differences.

Adolescent↗
PubMed2007

Speech outcome and velopharyngeal function in cleft palate: comparison of Le Fort I maxillary osteotomy and distraction osteogenesis--early results.

OBJECTIVE: To compare speech outcome and velopharyngeal (VP) status of subjects with repaired cleft palate who underwent either conventional Le Fort I osteotomy or maxillary distraction osteogenesis to correct maxillary hypoplasia. DESIGN: Prospective randomized study with blind assessment of speech outcome and VP status. SUBJECTS: Twenty-two subjects were randomized into conventional Le Fort I osteotomy and Le Fort I distraction groups. All were native Chinese (Cantonese) speakers. METHOD: Perceptual judgment of resonance and nasal emission, study of VP structures by nasoendoscopy, and instrumental measurement by nasometry. Assessments were performed preoperatively and at 3 months postoperatively. MAIN OUTCOME MEASURES: Assessment of VP closure, perceptual rating of hypernasality and nasal emission, nasalance, and amount of maxillary advancement. RESULTS: There was no statistical difference in any of the outcome measures between the 10 subjects with conventional Le Fort I osteotomy and the 12 subjects with maxillary distraction: hypernasality (chi-square = 3.850, p = 0.221), nasal emission (chi-square = 0.687, p = 0.774), VP gap size (chi-square = 1.527, p = 0.635, and nasalance (t = -0.145, p = 0.886). There was no correlation between amount of maxillary advancement and any of the outcome measures (p = .05 for all). Changes in VP gap size and resonance are described. CONCLUSION: Results need to be interpreted with caution because of the small sample size and early follow-up. However, this study utilized an assessment protocol involving a variety of outcome measures and careful consideration of reliability factors, which can be a model for further and follow-up studies.

Adolescent↗
PubMed1986

Flupentixolhydrochloride in low dosages: effects on perceptual and psychomotor performance in emotionally stable and emotionally labile healthy subjects.

Effects of flupentixol on performance were evaluated in a double-blind study with 107 healthy male subjects. Experimental factors were dosage (0, 1, and 2 mg Fluanxol 0.5/day), the trait variable 'neuroticism' (high vs. low score on a questionnaire scale), and time of measurement (before and after 4 days of treatment). Drug effects were measured by means of seven paper-and-pencil tests and eight apparatus tests covering the following cognitive functions: endurance in attention, spacial orientation, flexibility and speed of closure, perceptual speed, response speed, psychomotor coordination, knowledge of traffic rules, and basic motoric tempo. Univariate and multivariate ANOVAs disclosed that flupentixol has detrimental effects on perceptual and psychomotor functions, in particular when administered in a dosage of 2 mg/day. These treatment effects did not interact with the trait variable neuroticism. Nevertheless, there were substantial differences between emotionally stable and emotionally labile subjects in both absolute performance level and change of performance over time.

Adult↗
PubMed2005

A laminar cortical model of stereopsis and 3D surface perception: closure and da Vinci stereopsis.

A laminar cortical model of stereopsis and 3D surface perception is developed and simulated. The model describes how monocular and binocular oriented filtering interact with later stages of 3D boundary formation and surface filling-in in the LGN and cortical areas V1, V2, and V4. It proposes how interactions between layers 4, 3B, and 2/3 in V1 and V2 contribute to stereopsis, and how binocular and monocular information combine to form 3D boundary and surface representations. The model includes two main new developments: (1) It clarifies how surface-to-boundary feedback from V2 thin stripes to pale stripes helps to explain data about stereopsis. This feedback has previously been used to explain data about 3D figure-ground perception. (2) It proposes that the binocular false match problem is subsumed under the Gestalt grouping problem. In particular, the disparity filter, which helps to solve the correspondence problem by eliminating false matches, is realized using inhibitory interneurons as part of the perceptual grouping process by horizontal connections in layer 2/3 of cortical area V2. The enhanced model explains all the psychophysical data previously simulated by Grossberg and Howe (2003), such as contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, Panum's limiting case, the Venetian blind illusion, stereopsis with polarity-reversed stereograms, and da Vinci stereopsis. It also explains psychophysical data about perceptual closure and variations of da Vinci stereopsis that previous models cannot yet explain.

Animals↗
PubMed2006

Visuoperceptual learning in alcoholic Korsakoff syndrome.

Relative to the characteristically profound deficits of explicit memory, components of implicit memory remain largely intact in patients with alcohol-induced Korsakoff syndrome (KS). Perceptual priming occurs in KS and transfer of learning has been consistently observed on mirror reading, a perceptual reversal task. Although priming also occurs with fragmented pictures, a perceptual closure task, it is unclear whether transfer of learning can occur. This study examined visuoperceptual learning in 4 men with alcoholic KS, 9 recently detoxified alcoholic men (ALC), 21 healthy age-matched normal control men (NC), and 6 young normal control men (YNC). Subjects were tested with the Gollin Incomplete Pictures Test at initial and 1-hour and 1-day retest sessions. Both alcoholic groups (KS, ALC) were impaired in visuoperceptual ability. All subject groups showed visuoperceptual learning. The KS group showed additional learning after continued exposure to the stimuli, despite their nonmnemonic visuospatial deficits and profound explicit memory impairment for the test stimuli. Transfer of learning to similar but new stimuli was not evident in either the KS or young healthy control subjects; learning occurred only for the specific items presented. The persistence of learning beyond the life of the percept, which was independent of declarative features (such as item recall), suggests that perceptual learning and memory reflects an intact cognitive memory process in KS. This process is likely mediated by posterior cortical networks relatively unaffected in KS and that are independent of the hippocampal-diencephalic declarative memory system.

Aged↗