Distractor Group Research Articles

Testing the effects of perceptual grouping on visual search in older adults

Visual search is to find targets while ignoring distractors. Previous studies established that a target is more difficult to identify if aligned collinearly with other items, called the collinear search impairment. Since older adults have lower perceptual grouping ability than younger adults, benefits in visual search may occur for older adults for they may be less distracted by the collinear distractors. Three experiments were carried out to compare 45 younger and 45 older healthy adults. Participants were asked to identify a local target either in the column with items collinearly aligned to each other (the overlapping condition) or in the background (the non-overlapping condition), and the response difference between the two conditions is the collinear search impairment. Results showed that both groups showed reliable search impairment specific to collinear distractor regardless of grouping difficulty and task demands, and the impairment strength increased with the grouping strength of the collinear distractor. Further analysis revealed that the response times of older adults increased in a multiplicative manner to that of younger adults, suggesting that longer response of older adults spread to multiple underlying processing including grouping and suppression of collinear distractors. Together, the results suggest that older adults were still distracted in visual search even when grouping was required on a distractor. Our findings also highlight how general slowing may delay suppression processing in visual search.

How fixation durations are affected by search difficulty manipulations

ABSTRACT Many eye tracking studies of visual search have focused on the role of the number of fixations and the nature of scan paths. Less attention has been paid to fixation durations and to how those durations are affected by stimulus features. Previous studies have shown that fixation durations can be as important as the number of fixations in explaining search times with complex stimuli (e.g., in search for specific faces). In the present study, simple stimuli were used in a search experiment where participants searched for a closed ring among rings with a gap. We manipulated distractor heterogeneity (DH), target-distractor similarity (TDS), and stimulus density (SDY, set size within a constant search window), and estimated the contributions of these factors to gaze behaviour and trial search time. The results show that fixation durations contribute less to variation in overall search time with simple search stimuli as compared to previous studies with more complex stimuli. However, fixation durations still increased with DH, TDS, and SDY. These effects were mainly additive, and we did not find an interaction between DH and closer element spacing at high levels of SDY that might have been expected since both DH and SDY influence distractor grouping.

Effects of Closed Reduction and Interlock Nailing of Femoral Shaft Fractures by Traction Table Vs Modified NA Fixator

Background: Femoral fractures are common fractures in orthopedics. Aim: To study the outcomes in patients with fracture shaft of femur, managed by close reduction and Inter Locking nail by traction table versus modified Naseer Awais fixator. Study design: Non randomized clinical study. Methodology: One hundred patients (50 in each group) were included in present study. Inter Lock femoral nailing was done in group A by TM distractor. Traction table was used in group B for the same procedure. Number of fluoroscope images per procedure, operation duration/time, contact between fracture fragments after reduction, limb rotation, limb length discrepancy, union time (radiological) and frequency of infection occurrence was noted and compared between the above said two groups. Results: Number of images per-operatively were 38.55±19.087, in group A 43.08±23.67, in group B 34.02±11.56 (P=0.017). The operative time in group A was 81.40±25.95 mins. The limb length discrepancy after surgery was 0.17±0.49 cm. The time of radiological union was 5.62±2.29 months in group A, versus 5.44±3.32 months in group B (P=0.753). Conclusion: We concluded that TM distractor group has comparable outcome with traction table group because there was no statistically significant difference in terms of operation duration/time, contact of major fracture fragments after reduction, limb length discrepancy (LLD), union (radiological), non-union and frequency of infection. However numbers of images in a procedure were less in traction table group in our study. Keywords: TM Distractor, Femoral Nail, Traction Table, Modified NA Fixator and Inter Lock Nail.

Minimally invasive surgery for intra-articular calcaneus fractures: a 9-year, single-center, retrospective study of a standardized technique using a 2-point distractor

BackgroundA fracture of the calcaneus can be a painful and disabling injury. Treatment modalities may be conservative or operative. Surgical treatment strategies include open reduction and internal fixation (ORIF) techniques, as well as a variety of minimally invasive methods. The aim of this study was to evaluate the treatment options and post-treatment complication rates for intra-articular calcaneal fractures at the Traumacenter Linz over a 9-year period.MethodsAll patients with calcaneal fractures treated at the Traumacenter Linz between 2007 and 2015 were included in this study. The patients records were retrospectively reviewed, and the data, including demographic parameters, cause of injury, and the time between injury and operative treatment were analyzed. The number of secondary operative interventions due to soft-tissue complications, hardware removal, and the long-term arthrodesis rate were evaluated.ResultsA minimally invasive 2-point-distractor method was used in 85.8% (n = 182) of all operatively managed calcaneal fractures (n = 212) in our department. The majority of the operations (88.7%) were performed within 2 days after the accident. The secondary operation rate resulting from wound complications was 2.7% in the 2-point distractor group and 16.7% in the ORIF group. A secondary arthrodesis was performed in 4.7% (n = 9) of the subtalar joints in the entire study population.ConclusionsOur data supported the assumption that severe wound complications would be less likely to occur after minimally invasive treatment compared to ORIF treatment. The rate of secondary arthrodesis in the study cohort was comparable to that in the literature.Level of evidenceIV

Subitizing, unlike estimation, does not process sets in parallel

Enumeration of very small quantities is a common task that we perform everyday. Much research has highlighted that in these conditions humans display fast, near errorless performance, a phenomenon dubbed subitizing. It has been suggested that this regime has a pivotal role in numerosity perception. Here we asked if this system can process multiple sets of items in parallel. At odds with what happens for moderate numerosities, we found a strong impairment caused already by the introduction of a second group of items marked by a different color. Adding shape as a cue provided no benefit. The only case in which subitizing was possible was when the target and distractor group were held constant through the experimental block. These results show the surprising fact that whilst being rapid and errorless, subitizing does not have the capability to disentangle multiple groups of items and deals only with coarse stimulus statistics.

A Modified Inverted Nipple Correction Technique That Preserves Breastfeeding.

An inverted nipple may affect the appearance of the breasts and breastfeeding, but traditional surgical procedures might injure the normal lactiferous ducts and damage sensory functions. The aim of the study was to propose a minimally invasive and reliable method that preserves breastfeeding and corrects grade I and II inverted nipples. This was a randomized controlled trial of 230 female patients with unilateral or bilateral inverted nipples and 30 patients with normal nipples who visited the Preconception Counseling Department of our hospital from February 2009 to January 2016. The nipples in the distractor group underwent an operation with a distractor, while the control nipples were treated with daily exercises. The intervention lasted 6 months. The primary endpoint was full-term pregnancy breastfeeding for 4 months. The secondary endpoint was the completion of lactation without obvious complications, such as mastitis and nipple craze. Grade I and II nipples achieved increased height after the distractor was worn for 6 months and at 37 weeks of pregnancy (P < 0.05), while the control nipples achieved only a marginal improvement at 37 weeks of pregnancy. In the distractor group, the success rates were 84.9% and 79.3% for grade I and II nipples, respectively, compared with the control group (52.5% and 38.9%, respectively) (P < 0.05). After treatment with the distractor for 6 months, nipples in the distractor group showed no complications, such as skin numbness or nipple necrosis. The use of a distractor is a reliable and minimally invasive method for correcting grade I and II inverted nipples while preserving breastfeeding.

Brain activation of semantic category-based grouping in multiple identity tracking task.

Using Multiple Identity Tracking task and the functional magnetic resonance imaging (fMRI) technology, the present study aimed to isolate and visualize the functional anatomy of neural systems involved in the semantic category-based grouping process. Three experiment conditions were selected and compared: the category-based targets grouping (TG) condition, the targets-distractors grouping (TDG) condition and the homogenous condition. In the TG condition, observers could utilize the categorical distinction between targets and distractors, to construct a uniform presentation of targets, that is, to form a group of the targets to facilitate tracking. In the TDG condition, half the targets and half the distractors belonged to the same category. Observers had to inhibit the grouping of targets and distractors in one category to complete tracking. In the homogenous condition, where targets and distractors consisted of the same objects, no grouping could be formed. The “TG-Homogenous” contrast (p<0.01) revealed the activation of the left fusiform and the pars triangularis of inferior frontal gyrus (IFG). The “TG-TDG” contrast only revealed the activation of the left anterior cingulate gyrus (ACC). The fusiform and IFG pars triangularis might participate in the representation of semantic knowledge, IFG pars triangularis might relate intensely with the classification of semantic categories. The ACC might be responsible for the initiation and maintenance of grouping representation.

Feasibility of Stifle Medial Meniscal Release in Toy Breed Dogs with and without a Joint Distractor.

To investigate the feasibility of medial meniscal release (MMR) during stifle arthroscopy in toy breed dogs with and without a joint distractor. Experimental cadaveric study. Stifles (n = 40) from 20 canine cadavers (1.8-5.1 kg). Paired stifles were randomly assigned to the joint distractor group and the control group (n = 20 each). All stifles underwent arthroscopic transection of the cranial cruciate ligament followed by a release of the caudomedial meniscotibial ligament. After the procedures, all stifles were disarticulated. The degree of released meniscus was recorded subjectively by 5% increments. A MMR success was defined as a complete transection. The areas of femoral and tibial articular cartilage damage were calculated using india ink staining and digital imaging. The results were compared between groups and odds ratios were calculated. All stifle arthroscopies were successful. The success rate of MMR was significantly higher (P = .013) with a joint distractor than without a joint distractor. MMR was 7.4 times more likely to succeed with a joint distractor than without a joint distractor. The distal femoral articular cartilage was significantly more damaged (P = .011) in the stifles without a joint distractor than in the stifles with a distractor. No difference was found between the 2 groups for damage to the tibial cartilage (P = .058). Stifle arthroscopic MMR is feasible in toy breed dogs. Using a joint distractor is recommended for arthroscopic treatment based on our results because it significantly reduced the rate of incomplete release as well as iatrogenic cartilage damage.

Counting within the Subitizing Range: The Effect of Number of Distractors on the Perception of Subset Items

When exploring the mechanisms involved in perceiving numbers we must distinguish between two types of numbers: subset numbers (e.g., perceiving "2" when two plates and one cup are displayed on a table) and the total number of items (e.g., perceiving "3" objects in the previous example). Combining feature perception theories with number perception theories, the current paper explores the mechanisms involved in the perception of small numbers in feature-defined subsets. The paper introduces several theories for how subset items can be represented and examines an important prediction of those theories: Will the number of distractors affect the perception of small subset items? In two experiments, we found that the response time (RT) for counting small target items that differ from their distractors by a single feature was faster when there were few distractors compared to many distractors. This was found for different types of distractors: distractors within and outside the subitizing range. Only when distractors were organized in a specific pattern, allowing distractor grouping, the increase in the number of distractors did not affect target counting. The current study suggests that even when performing simple counting of subset targets, the enumeration process can begin only once the locations of the targets have been identified and the targets' shape is bound to these locations. This pre-counting procedure depends on the number of individual locations occupied by the distractors. These findings are further discussed within the context of the object file theory.

Skeletal and dental effects of tooth-borne versus hybrid devices for mandibular symphyseal distraction osteogenesis

To evaluate and compare, retrospectively, the skeletal and dental effects of mandibular symphyseal distraction osteogenesis (MSDO) achieved through the use of tooth-borne versus hybrid distractors. Pretreatment (T1), predistraction (T2), postdistraction (T3), and posttreatment (T4) orthodontic records were collected and analyzed for 47 patients (20 tooth-borne, 27 hybrid). At each time point, records included intraoral photographs, study models, postero-anterior cephalometric radiographs, and lateral cephalometric radiographs. Submental vertex radiographs were taken at T2, T3, and T4. Changes in a total of 18 measurements were analyzed to compare patients undergoing tooth-borne versus hybrid distraction. The cumulative effects of orthodontics and MSDO produced similar gains in measured arch widths, with a decreased irregularity index in both groups (P > .05). However, there were differences in the timing during which the expansion was achieved. The hybrid distractor group gained space during the distraction phase of treatment. The tooth-borne group showed greater gains during pre- and postdistraction orthodontics. Comparisons of intercanine and interbone marker widths demonstrated a more parallel separation of bone during distraction with the hybrid distractor (P < .001). Distraction with the tooth-borne distractor was disproportionate, with greater separation of the canines in alveolar bone than of the bone markers in basal bone. During postdistraction orthodontics, the tooth-borne distractor group showed statistically greater increases in measurements. Both skeletal and dental expansion was achieved with both appliances. Greater skeletal expansion was achieved with a hybrid distractor. Greater dental expansion was achieved with a tooth-borne distractor.

Taking Conjunction Search to a Higher Dimension

In visual search for conjunctions, targets are defined by combinations of features. Thus, targets might be RED VERTICAL items among RED horizontal and green VERTICAL distractors. Guided Search and similar models argue that features are conjoined only once an object is attended. However, efficient conjunction search is possible because observers can guide attention toward red and toward vertical. Real-world objects may be defined by the conjunction of many features, with no one feature defining the target. Can attention be guided to higher order conjunctions? We created 6D conjunction stimuli and varied the number of features shared between targets and distractors and the number of distractor types. RT x set size slopes range from 1.4 msec/item when two distractor types each share three features with the target to 66 msec/item when six distractor types each share five features with the target. Using different 3D conjunctions, we held distributions of features constant (1/3 of each of three colors, shapes, and orientations). We varied the grouping of distractors in order to look for evidence of simultaneous guidance by multiple attributes versus sequential grouping of subsets (Find the odd orientation in this color subset). We find that guidance and grouping may both contribute to efficient conjunction search.

Perceptual grouping, not emotion, accounts for search asymmetries with schematic faces.

Several different explanations have been proposed to account for the search asymmetry (SA) for angry schematic faces (i.e., the fact that an angry face target among friendly faces can be found faster than vice versa). The present study critically tested the perceptual grouping account, (a) that the SA is not due to emotional factors, but to perceptual differences that render angry faces more salient than friendly faces, and (b) that the SA is mainly attributable to differences in distractor grouping, with angry faces being more difficult to group than friendly faces. In visual search for angry and friendly faces, the number of distractors visible during each fixation was systematically manipulated using the gaze-contingent window technique. The results showed that the SA emerged only when multiple distractors were visible during a fixation, supporting the grouping account. To distinguish between emotional and perceptual factors in the SA, we altered the perceptual properties of the faces (dented-chin face) so that the friendly face became more salient. In line with the perceptual account, the SA was reversed for these faces, showing faster search for a friendly face target. These results indicate that the SA reflects feature-level perceptual grouping, not emotional valence.

Measurement of Auditory Cues in Drivers' Distraction

A driving simulator was used to examine the effects on driving performance of auditory cues in an in-vehicle information search task. Drivers' distraction by the search tasks was measured on a peripheral detection task. The difficulty of the search task was systematically varied to test the distraction caused by a quantified visual load. 58 participants completed the task. Performance on both search tasks and peripheral detection tasks was measured by mean response time and percent error. Analyses indicated that in-vehicle information search performance can be severely degraded when a target is located within a group of diverse distractors. Inclusion of an auditory cue in the visual search increased the mean response time as a result of a change in modality from auditory to visual. Inclusion of such an auditory cue seemed to influence distraction as measured by performance on the peripheral detection task; accuracy was lower when auditory cues were provided, and responses were slower when no auditory cues were provided. Distraction by the auditory cue varied according to the difficulty of the search task.

Perceptual organization and visual search processes during target detection task performance in schizophrenia, as revealed by fMRI

BackgroundPast studies of perceptual organization in schizophrenia have demonstrated impairments binding fragmented stimulus components into unified representations. ERP and fMRI data indicate that even under conditions of adequate behavioral task performance, significant and meaningful changes in cortical and subcortical activation are present. Here, we examined, using fMRI, activation differences on a visual task wherein feature grouping was a precursor to the formation of distinct groups in the service of target location and identification. MethodFourteen schizophrenia patients and 16 healthy controls completed a target detection task with 2 conditions: one in which target–distractor grouping facilitates detection (the Isolated condition) and one in which it hinders detection (the Embedded condition). Stimuli were blocked by condition. Accuracy and RT data were obtained in addition to fMRI data. ResultsPatients and controls did not differ significantly in accuracy or RT in either condition. Within this context, controls demonstrated greater recruitment of brain regions involved in visual–spatial processing, and the groups differed in activity in areas known to support visual search, visual analysis, decision making and response generation. ConclusionThese findings are consistent with past data indicating reduced processing of stimulus organization, and the subsequent use of inefficient visual search strategies, even under conditions when behavioral performance is at a high level and matches that of healthy controls.

Large bone distractor for open reconstruction of articular fractures of the calcaneus

The results of operative treatment of two groups of patients with articular fractures of the calcaneus were evaluated. Twenty-three cases were treated surgically using a standard reconstruction procedure. In the second group of 19 patients a large bone distractor was used; it held the soft tissue flap retracted, while aiding in articular and tuberosity fragment reduction and increasing visualisation by distraction of the posterior talocalcaneal joint. After a year, the anatomical and functional results, together with the operative time, were evaluated. All fractures healed with good or very good anatomical results. All cases, except those with complications (n = 3), achieved good (n = 28) or very good (n = 11) functional scoring. The distractor group had significantly shorter operative times, and less manpower was needed during surgery. We conclude that the large bone distractor is a useful tool in open reconstruction of articular calcaneal fractures.

What Is the Evidence for Use Dependent Learning After Stroke?

Our laboratory has been interested in the patterns of synaptic plasticity after cortical stroke in animal models.1 These protein expression studies suggest that regions both ipsilateral and contralateral to the stroke are involved during the recovery period. An emerging issue of interest is whether the recovered function is indeed normal or reflects some compensatory function.2 One approach to resolving these questions is to assess different patterns of functional recovery in patients who do and do not recover function with and without therapy and compare them to normal patterns. Investigation of the molecular mechanisms of brain plasticity after injury suggests that functional activity stimulates this recovery and guides the development of functional pathways.3,4 Several investigators postulate that recovery from stroke resembles “use-dependent” learning.5 For this report, we review pertinent literature related to this phenomenon, assess how recovery of language resembles normal language function, and provide examples from our own research on functional imaging that assess patterns of activation related to recovery. The primary treatment modality that we review is constraint-induced language therapy (CILT), in which stroke patients are restricted to using verbal communication.6 CILT is based on principles of constraint-induced therapy for other conditions.6 CILT is performed in chronic stroke …

No previews are good news: Using preview search to probe categorical grouping for orientation

We used the preview search procedure (Watson, D. G., & Humphreys G. W. (1997). Prioritising selection for new objects by top–down attentional inhibition of old objects. Psychological Review, 104, 90–122.) to examine distractor grouping in visual search for categorically-defined targets in the orientation dimension (Wolfe, J. M., Friedman-Hill, S. R., Stewart, M. I., & O’Connell, K. M. (1992). The role of categorization in visual search for orientation. Journal of Experimental Psychology: Human Perception and Performance, 18, 34–49). Participants searched for a relatively steep target presented amongst distractors of two shallow orientations. In a preview condition, the different distractors were presented in different time steps and search was found to be worse than a full-set baseline (Experiment 1). Further experiments determined this was not due to attentional capture by new distractors that were steeper than old items, nor to participants using different search strategies in the preview and full-set baselines. However, there were costs to performance when the old distractor group differed in orientation from the new distractors. We attribute the results to the preview condition disrupting grouping between distractors, with the different distractor groups then competing for selection with the target. An examination of the time-course of the preview effect suggested that grouping and segmentation was fast-acting, and separate from a process such as visual marking, involving the slow suppression of distractors over time. Under asynchronous presentation conditions, preview and new distractors that differ from the target orientation category, can compete rather than cooperate in grouping.

Contextual cueing in naturalistic scenes: Global and local contexts.

In contextual cueing, the position of a target within a group of distractors is learned over repeated exposure to a display with reference to a few nearby items rather than to the global pattern created by the elements. The authors contrasted the role of global and local contexts for contextual cueing in naturalistic scenes. Experiment 1 showed that learned target positions transfer when local information is altered but not when global information is changed. Experiment 2 showed that scene-target covariation is learned more slowly when local, but not global, information is repeated across trials than when global but not local information is repeated. Thus, in naturalistic scenes, observers are biased to associate target locations with global contexts.

Effects of perceptual grouping on positive and negative priming

The effects of perceptual grouping/segregation of targets and distractors by means of colour on positive and negative priming were examined in two experiments. In Experiments 1 and 2 we examined whether grouping of target and distractors by means of common colour in the prime display affected positive and negative priming, or whether these effects depend on prime–probe contextual similarity in colour. In addition, we examined the effects of the predictability of target colour in the prime and the probe displays across the experiments using mixed (Experiment 1) or blocked procedures (Experiment 2). The pattern of results was similar in both experiments, indicating that the positive priming effect was determined by target repetition and enhanced by perceptual segregation of target from distractors in the prime display. The negative priming effect was determined by grouping the target and distractors by common colour in the prime display. The results of the present experiments are consistent with inhibition-based models of negative priming.

Color-based grouping and inhibition in visual search: Evidence from a probe detection analysis of preview search

In four experiments, we examined selection processes in visual search using a probe detection task to measure the allocation of attention. Under preview search conditions, probes were harder to detect on old relative to new distractors (Experiment 1). This cannot be attributed solely to low-level sensory factors (Experiment 2). In addition, probe detection was sensitive to color-based grouping of old distractors and to color similarity between old distractors (Experiments 3 and 4). These effects were dissociated when the color of the old distractors changed but probe detection effects remained. Collectively, the data indicate both group-based suppression of distractors and the separate inhibition of distractor features in search.