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1

Effect of mammographic breast density on radiologists' visual search pattern  

NASA Astrophysics Data System (ADS)

This study investigates the impact of breast density on visual searching pattern. A set of 74 one-view malignancy containing mammographic images were examined by 7 radiologists. Eye position was recorded and visual search parameters such as total time examining a case, time to hit the lesion, dwell time and number of hits per area were collected. Fixations were calculated in 3 areas of interests: background breast parenchyma, dense areas of parenchyma and lesion. Significant increases in dwell time and number of hits in dense areas of parenchyma were noted for highcompared to low- mammographic density images when the lesion overlay the fibroglandular tissue (p<0.01). When the lesion was outside the fibroglandular tissue, significant increase in dwell time and number of hits in dense areas of parenchyma in high- compared to low- mammographic density images were observed (p<0.01). No significant differences have been found in total time examining a case, time to first fixate the lesion, dwell time and number of hits in background breast parenchyma and lesion areas. In conclusion, our data suggests that dense areas of breast parenchyma attract radiologists' visual attention. Lesions overlaying the fibroglandular tissue were detected faster, therefore lesion location, whether overlaying or outside the fibroglandular tissue, appeared to have an impact on radiologists' visual searching pattern.

Al Mousa, Dana S.; Brennan, Patrick C.; Ryan, Elaine A.; Lee, Warwick B.; Pietrzyk, Mariusz W.; Reed, Warren M.; Alakhras, Maram M.; Li, Yanpeng; Mello-Thoms, Claudia

2014-03-01

2

Statistical patterns of visual search for hidden objects  

PubMed Central

The movement of the eyes has been the subject of intensive research as a way to elucidate inner mechanisms of cognitive processes. A cognitive task that is rather frequent in our daily life is the visual search for hidden objects. Here we investigate through eye-tracking experiments the statistical properties associated with the search of target images embedded in a landscape of distractors. Specifically, our results show that the twofold process of eye movement, composed of sequences of fixations (small steps) intercalated by saccades (longer jumps), displays characteristic statistical signatures. While the saccadic jumps follow a log-normal distribution of distances, which is typical of multiplicative processes, the lengths of the smaller steps in the fixation trajectories are consistent with a power-law distribution. Moreover, the present analysis reveals a clear transition between a directional serial search to an isotropic random movement as the difficulty level of the searching task is increased.

Credidio, Heitor F.; Teixeira, Elisangela N.; Reis, Saulo D. S.; Moreira, Andre A.; Andrade Jr, Jose S.

2012-01-01

3

Mining compact bag-of-patterns for low bit rate mobile visual search.  

PubMed

Visual patterns, i.e., high-order combinations of visual words, contributes to a discriminative abstraction of the high-dimensional bag-of-words image representation. However, the existing visual patterns are built upon the 2D photographic concurrences of visual words, which is ill-posed comparing with their real-world 3D concurrences, since the words from different objects or different depth might be incorrectly bound into an identical pattern. On the other hand, designing compact descriptors from the mined patterns is left open. To address both issues, in this paper, we propose a novel compact bag-of-patterns (CBoPs) descriptor with an application to low bit rate mobile landmark search. First, to overcome the ill-posed 2D photographic configuration, we build up a 3D point cloud from the reference images of each landmark, therefore more accurate pattern candidates can be extracted from the 3D concurrences of visual words. A novel gravity distance metric is then proposed to mine discriminative visual patterns. Second, we come up with compact image description by introducing a CBoPs descriptor. CBoP is figured out by sparse coding over the mined visual patterns, which maximally reconstructs the original bag-of-words histogram with a minimum coding length. We developed a low bit rate mobile landmark search prototype, in which CBoP descriptor is directly extracted and sent from the mobile end to reduce the query delivery latency. The CBoP performance is quantized in several large-scale benchmarks with comparisons to the state-of-the-art compact descriptors, topic features, and hashing descriptors. We have reported comparable accuracy to the million-scale bag-of-words histogram over the million scale visual words, with high descriptor compression rate (approximately 100-bits) than the state-of-the-art bag-of-words compression scheme. PMID:24835227

Ji, Rongrong; Duan, Ling-Yu; Chen, Jie; Huang, Tiejun; Gao, Wen

2014-07-01

4

Comparison of the effects of superior colliculus and pulvinar lesions on visual search and tachistoscopic pattern discrimination in monkeys  

Microsoft Academic Search

In order to investigate whether pulvinar lesions produce behavioral impairments similar to those that follow superior colliculus lesions, monkeys were tested on a visual search task before and after receiving radiofrequency lesions of either the superior colliculus or pulvinar. The animals searched for a small target pattern within an array of varying numbers of irrelevant patterns. After receiving colliculus lesions,

D. B. Bender; C. M. Butter

1987-01-01

5

Visual search patterns in semantic dementia show paradoxical facilitation of binding processes  

PubMed Central

While patients with Alzheimer’s disease (AD) show deficits in attention, manifested by inefficient performance on visual search, new visual talents can emerge in patients with frontotemporal lobar degeneration (FTLD), suggesting that, at least in some of the patients, visual attention is spared, if not enhanced. To investigate the underlying mechanisms for visual talent in FTLD (behavioral variant FTD [bvFTD] and semantic dementia [SD]) patients, we measured performance on a visual search paradigm that includes both feature and conjunction search, while simultaneously monitoring saccadic eye movements. AD patients were impaired relative to healthy controls (NC) and FTLD patients on both feature and conjunction search. BvFTD patients showed less accurate performance only on the conjunction search task, but slower response times than NC on all three tasks. In contrast, SD patients were as accurate as controls and had faster response times when faced with the largest number of distracters in the conjunction search task. Measurement of saccades during visual search showed that AD patients explored more of the image, whereas SD patients explored less of the image before making a decision as to whether the target was present. Performance on the conjunction search task positively correlated with gray matter volume in the superior parietal lobe, precuneus, middle frontal gyrus and superior temporal gyrus. These data suggest that despite the presence of extensive temporal lobe degeneration, visual talent in SD may be facilitated by more efficient visual search under distracting conditions due to enhanced function in the dorsal frontoparietal attention network.

Viskontas, Indre V.; Boxer, Adam L.; Fesenko, John; Matlin, Alisa; Heuer, Hilary W.; Mirsky, Jacob; Miller, Bruce L.

2011-01-01

6

The visual search patterns and hazard responses of experienced and inexperienced motorcycle riders.  

PubMed

Hazard perception is a critical skill for road users. In this study, an open-loop motorcycle simulator was used to examine the effects of motorcycle riding and car driving experience on hazard perception and visual scanning patterns. Three groups of participants were tested: experienced motorcycle riders who were experienced drivers (EM-ED), inexperienced riders/experienced drivers (IM-ED), and inexperienced riders/inexperienced drivers (IM-ID). Participants were asked to search for hazards in simulated scenarios, and click a response button when a hazard was identified. The results revealed a significant monotonic decrease in hazard response times as experience increased from IM-ID to IM-ED to EM-ED. Compared to the IM-ID group, both the EM-ED and IM-ED groups exhibited more flexible visual scanning patterns that were sensitive to the presence of hazards. These results point to the potential benefit of training hazard perception and visual scanning in motorcycle riders, as has been successfully demonstrated in previous studies with car drivers. PMID:19887160

Hosking, Simon G; Liu, Charles C; Bayly, Megan

2010-01-01

7

Linking physiology with behaviour: Functional specialisation of the visual field is reflected in gaze patterns during visual search  

Microsoft Academic Search

Based on neurophysiological findings and a grid to score binocular visual field function, two hypotheses concerning the spatial distribution of fixations during visual search were tested and confirmed in healthy participants and patients with homonymous visual field defects. Both groups showed significant biases of fixations and viewing time towards the centre of the screen and the upper screen half. Patients

Tobias Pflugshaupt; Roman von Wartburg; Pascal Wurtz; Silvia Chaves; Anouk Déruaz; Thomas Nyffeler; Sebastian von Arx; Mathias Luethi; Dario Cazzoli; René M. Mueri

2009-01-01

8

Linking physiology with behaviour: Functional specialisation of the visual field is reflected in gaze patterns during visual search.  

PubMed

Based on neurophysiological findings and a grid to score binocular visual field function, two hypotheses concerning the spatial distribution of fixations during visual search were tested and confirmed in healthy participants and patients with homonymous visual field defects. Both groups showed significant biases of fixations and viewing time towards the centre of the screen and the upper screen half. Patients displayed a third bias towards the side of their field defect, which represents oculomotor compensation. Moreover, significant correlations between the extent of these three biases and search performance were found. Our findings suggest a new, more dynamic view of how functional specialisation of the visual field influences behaviour. PMID:19022277

Pflugshaupt, Tobias; von Wartburg, Roman; Wurtz, Pascal; Chaves, Silvia; Déruaz, Anouk; Nyffeler, Thomas; von Arx, Sebastian; Luethi, Mathias; Cazzoli, Dario; Mueri, René M

2009-01-01

9

Eye movement trajectories in active visual search: Contributions of attention, memory, and scene boundaries to pattern formation  

Microsoft Academic Search

We relate the roles of attention, memory, and spatial constraints to pattern formation in eye movement trajectories previously\\u000a measured in a conjunctive visual search task. Autocorrelations and power spectra of saccade direction cosines confirm a bias\\u000a to progress forwardly, while turning at the display boundaries, plus a long-range memory component for the search path. Analyses\\u000a of certain measures of circulation

T. D. Keech; L. Resca

2010-01-01

10

NCI Visuals Online: Search  

Cancer.gov

Skip Navigation NCI Visuals Online Home About My Pictures Browse Search Quick Search Search Search for: Date Created: Any 1900 1920 1940 1960 1980 1990 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 to Any 1900 1920 1940 1960 1980 1990 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Sort

11

Linguistically Mediated Visual Search  

Microsoft Academic Search

During an individual's normal interaction with the envi- ronment and other humans, visual and linguistic signals often coin- cide and can be integrated very quickly. This has been clearly demonstrated in recent eyetracking studies showing that visual per- ception constrains on-line comprehension of spoken language. In a modified visual search task, we found the inverse, that real-time lan- guage comprehension

Michael J. Spivey; Melinda J. Tyler; Kathleen M. Eberhard; Michael K. Tanenhaus

2001-01-01

12

Visual search in clutter.  

PubMed

Detecting a target in clutter is particularly difficult because the observer must monitor many potential locations to find the target, and because the clutter itself might mask the target. To investigate whether contemporary models of search can account for visual search in clutter, we measured the detection of an oblique string of five aligned dots presented at an unknown location as a function of noise density. Observers judged which of two 200 ms intervals contained the signal string. At a given density, noise composed of oriented pairs of dots greatly degraded detection compared to random dot noise, especially if the paired noise shared the same orientation as the signal. Increasing the orientation difference between the paired noise and the signal improved detection, as did increasing signal length. We successfully modeled these results with an array of multi-scaled oriented detectors optimally tuned for the signal string. These results indicate that search for these simple patterns in noise is based on competing responses in oriented filters. PMID:15066387

Verghese, Preeti; McKee, Suzanne P

2004-06-01

13

Eye movement trajectories in active visual search: contributions of attention, memory, and scene boundaries to pattern formation.  

PubMed

We relate the roles of attention, memory, and spatial constraints to pattern formation in eye movement trajectories previously measured in a conjunctive visual search task. Autocorrelations and power spectra of saccade direction cosines confirm a bias to progress forwardly, while turning at the display boundaries, plus a long-range memory component for the search path. Analyses of certain measures of circulation and imbalance in the eye trajectories, and their relations with the display area correspondingly subtended, bear signatures of spiraling or circulating patterns. We interpret their prevalence as mainly due to the interactions between three basic psychoneural mechanisms (conspicuity area, forward bias, long-range memory) and two task-specific geometric-spatial constraints on the eye trajectories (central start and display confinement). Conversely, computer simulations of random walks in which all psychoneural mechanisms are eliminated, while geometric-spatial constraints are maintained, show no prevalence of circulating patterns by those measures. We did find certain peculiarities of some individual participants in their pattern selections, but they appear too casual and incidental to suggest more systematic or complex search strategies in our randomized displays of uninformative stimuli. PMID:20045884

Keech, T D; Resca, L

2010-01-01

14

Codex search patterns  

US Patent & Trademark Office Database

A search engine optimizer that works independently and in parallel with a browser and search engine supercomputer to gather, analyze, and distill input information interactively. The optimizer reorganizes the input, and providing an optimized version as an output. The optimized version of the input (e.g. output) is sent to the search engine that responds to the end user with search results. The optimizer recognizes each request as a pattern and stores the pattern in an advanced Glyph format. This permits the optimizer to identify a left and ride side checkmate combination required to achieve certitude.

2013-02-26

15

Visual Representation Determines Search Difficulty: Explaining Visual Search Asymmetries  

PubMed Central

In visual search experiments there exist a variety of experimental paradigms in which a symmetric set of experimental conditions yields asymmetric corresponding task performance. There are a variety of examples of this that currently lack a satisfactory explanation. In this paper, we demonstrate that distinct classes of asymmetries may be explained by virtue of a few simple conditions that are consistent with current thinking surrounding computational modeling of visual search and coding in the primate brain. This includes a detailed look at the role that stimulus familiarity plays in the determination of search performance. Overall, we demonstrate that all of these asymmetries have a common origin, namely, they are a consequence of the encoding that appears in the visual cortex. The analysis associated with these cases yields insight into the problem of visual search in general and predictions of novel search asymmetries.

Bruce, Neil D. B.; Tsotsos, John K.

2011-01-01

16

Hemispheric asymmetries in visual search  

Microsoft Academic Search

We conducted two visual search experiments, and found that target-detection accuracy and speed were better when the target was projected to the right hemisphere in the feature search condition and better when the target was projected to the left hemisphere in the feature-conjunction search condition. We propose that the highly efficient, so-called parallel search performance characteristic of feature search is

William Poynter; Candice Roberts

2011-01-01

17

Modeling Efficient Serial Visual Search.  

National Technical Information Service (NTIS)

Humans perform visual search fairly efficiently, finding targets within only a few fixations. Data from eye-tracked participants was subjected to a fixation by fixation analysis to pinpoint why participants tended to make fewer fixations than would be exp...

B. Z. Veksler W. D. Gray

2012-01-01

18

Parallel Processing in Visual Search Asymmetry  

ERIC Educational Resources Information Center

The difficulty of visual search may depend on assignment of the same visual elements as targets and distractors-search asymmetry. Easy C-in-O searches and difficult O-in-C searches are often associated with parallel and serial search, respectively. Here, the time course of visual search was measured for both tasks with speed-accuracy methods. The…

Dosher, Barbara Anne; Han, Songmei; Lu, Zhong-Lin

2004-01-01

19

Visual Search Remains Efficient when Visual Working Memory is Full  

Microsoft Academic Search

Many theories of attention have proposed that visual working memory plays an important role in visual search tasks. The present study examined the involvement of visual working memory in search using a dual-task paradigm in which participants performed a visual search task while maintaining no, two, or four objects in visual working memory. The presence of a working memory load

Geoffrey F. Woodman; Edward K. Vogel; Steven J. Luck

2001-01-01

20

Evolutionary pattern search algorithms  

SciTech Connect

This paper defines a class of evolutionary algorithms called evolutionary pattern search algorithms (EPSAs) and analyzes their convergence properties. This class of algorithms is closely related to evolutionary programming, evolutionary strategie and real-coded genetic algorithms. EPSAs are self-adapting systems that modify the step size of the mutation operator in response to the success of previous optimization steps. The rule used to adapt the step size can be used to provide a stationary point convergence theory for EPSAs on any continuous function. This convergence theory is based on an extension of the convergence theory for generalized pattern search methods. An experimental analysis of the performance of EPSAs demonstrates that these algorithms can perform a level of global search that is comparable to that of canonical EAs. We also describe a stopping rule for EPSAs, which reliably terminated near stationary points in our experiments. This is the first stopping rule for any class of EAs that can terminate at a given distance from stationary points.

Hart, W.E.

1995-09-19

21

Visualization of Pulsar Search Data  

NASA Astrophysics Data System (ADS)

The search for periodic signals from rotating neutron stars or pulsars has been a computationally taxing problem to astronomers for more than twenty-five years. Over this time interval, increases in computational capability have allowed ever more sensitive searches, covering a larger parameter space. The volume of input data and the general presence of radio frequency interference typically produce numerous spurious signals. Visualization of the search output and enhanced real-time processing of significant candidate events allow the pulsar searcher to optimally processes and search for new radio pulsars. The pulsar search algorithm and visualization system presented in this paper currently runs on serial RISC based workstations, a traditional vector based super computer, and a massively parallel computer. A description of the serial software algorithm and its modifications for massively parallel computing are describe. The results of four successive searches for millisecond period radio pulsars using the Arecibo telescope at 430 MHz have resulted in the successful detection of new long-period and millisecond period radio pulsars.

Foster, R. S.; Wolszczan, A.

1993-05-01

22

Supporting Web Search with Visualization  

Microsoft Academic Search

\\u000a One of the fundamental goals of Web-based support systems is to promote and support human activities on the Web. The focus\\u000a of this Chapter is on the specific activities associated with Web search, with special emphasis given to the use of visualization\\u000a to enhance the cognitive abilities of Web searchers. An overview of information retrieval basics, along with a focus

Orland Hoeber; Xue Dong Yang

2010-01-01

23

Development of a Computerized Visual Search Test  

ERIC Educational Resources Information Center

Visual attention and visual search are the features of visual perception, essential for attending and scanning one's environment while engaging in daily occupations. This study describes the development of a novel web-based test of visual search. The development information including the format of the test will be described. The test was designed…

Reid, Denise; Babani, Harsha; Jon, Eugenia

2009-01-01

24

Statistical templates for visual search.  

PubMed

How do we find a target embedded in a scene? Within the framework of signal detection theory, this task is carried out by comparing each region of the scene with a "template," i.e., an internal representation of the search target. Here we ask what form this representation takes when the search target is a complex image with uncertain orientation. We examine three possible representations. The first is the matched filter. Such a representation cannot account for the ease with which humans can find a complex search target that is rotated relative to the template. A second representation attempts to deal with this by estimating the relative orientation of target and match and rotating the intensity-based template. No intensity-based template, however, can account for the ability to easily locate targets that are defined categorically and not in terms of a specific arrangement of pixels. Thus, we define a third template that represents the target in terms of image statistics rather than pixel intensities. Subjects performed a two-alternative, forced-choice search task in which they had to localize an image that matched a previously viewed target. Target images were texture patches. In one condition, match images were the same image as the target and distractors were a different image of the same textured material. In the second condition, the match image was of the same texture as the target (but different pixels) and the distractor was an image of a different texture. Match and distractor stimuli were randomly rotated relative to the target. We compared human performance to pixel-based, pixel-based with rotation, and statistic-based search models. The statistic-based search model was most successful at matching human performance. We conclude that humans use summary statistics to search for complex visual targets. PMID:24627458

Ackermann, John F; Landy, Michael S

2014-01-01

25

Designing a Visual Interface for Online Searching.  

ERIC Educational Resources Information Center

"MedLine Search Assistant" is a new interface for MEDLINE searching that improves both search precision and recall by helping the user convert a free text search to a controlled vocabulary-based search in a visual environment. Features of the interface are described, followed by details of the conceptual design and the physical design of the…

Lin, Xia

1999-01-01

26

Visual exploration pattern in hemineglect  

Microsoft Academic Search

The analysis of eye movement parameters in visual neglect such as cumulative fixation duration, saccade amplitude, or the\\u000a numbers of saccades has been used to probe attention deficits in neglect patients, since the pattern of exploratory eye movements\\u000a has been taken as a strong index of attention distribution. The current overview of the literature of visual neglect has its\\u000a emphasis

René M. Müri; D. Cazzoli; T. Nyffeler; T. Pflugshaupt

2009-01-01

27

The development of organized visual search.  

PubMed

Visual search plays an important role in guiding behavior. Children have more difficulty performing conjunction search tasks than adults. The present research evaluates whether developmental differences in children's ability to organize serial visual search (i.e., search organization skills) contribute to performance limitations in a typical conjunction search task. We evaluated 134 children between the ages of 2 and 17 on separate tasks measuring search for targets defined by a conjunction of features or by distinct features. Our results demonstrated that children organize their visual search better as they get older. As children's skills at organizing visual search improve they become more accurate at locating targets with conjunction of features amongst distractors, but not for targets with distinct features. Developmental limitations in children's abilities to organize their visual search of the environment are an important component of poor conjunction search in young children. In addition, our findings provide preliminary evidence that, like other visuospatial tasks, exposure to reading may influence children's spatial orientation to the visual environment when performing a visual search. PMID:23584560

Woods, Adam J; Göksun, Tilbe; Chatterjee, Anjan; Zelonis, Sarah; Mehta, Anika; Smith, Sabrina E

2013-06-01

28

Collinearity Impairs Local Element Visual Search  

ERIC Educational Resources Information Center

In visual searches, stimuli following the law of good continuity attract attention to the global structure and receive attentional priority. Also, targets that have unique features are of high feature contrast and capture attention in visual search. We report on a salient global structure combined with a high orientation contrast to the…

Jingling, Li; Tseng, Chia-Huei

2013-01-01

29

Visual tracking using the harmony search algorithm  

Microsoft Academic Search

The harmony search algorithm is a meta-heuristic optimisation algorithm that mimics the improvisation process of musicians in a band or orchestra. A novel application of the harmony search algorithm is presented as it is applied to the visual tracking problem. A novel adaptation is made to the harmony search algorithm to improve performance under occlusion and is compared with a

Jaco Fourie; Steven Mills; Richard Green

2008-01-01

30

Cascade category-aware visual search.  

PubMed

Incorporating image classification into image retrieval system brings many attractive advantages. For instance, the search space can be narrowed down by rejecting images in irrelevant categories of the query. The retrieved images can be more consistent in semantics by indexing and returning images in the relevant categories together. However, due to their different goals on recognition accuracy and retrieval scalability, it is hard to efficiently incorporate most image classification works into large-scale image search. To study this problem, we propose cascade category-aware visual search, which utilizes weak category clue to achieve better retrieval accuracy, efficiency, and memory consumption. To capture the category and visual clues of an image, we first learn category-visual words, which are discriminative and repeatable local features labeled with categories. By identifying category-visual words in database images, we are able to discard noisy local features and extract image visual and category clues, which are hence recorded in a hierarchical index structure. Our retrieval system narrows down the search space by: 1) filtering the noisy local features in query; 2) rejecting irrelevant categories in database; and 3) preforming discriminative visual search in relevant categories. The proposed algorithm is tested on object search, landmark search, and large-scale similar image search on the large-scale LSVRC10 data set. Although the category clue introduced is weak, our algorithm still shows substantial advantages in retrieval accuracy, efficiency, and memory consumption than the state-of-the-art. PMID:24760907

Zhang, Shiliang; Tian, Qi; Huang, Qingming; Gao, Wen; Rui, Yong

2014-06-01

31

Distributed Search and Pattern Matching  

NASA Astrophysics Data System (ADS)

Peer-to-peer (P2P) technology has triggered a wide range of distributed applications including file-sharing, distributed XML databases, distributed computing, server-less web publishing and networked resource/service sharing. Despite of the diversity in application, these systems share common requirements for searching due to transitory nodes population and content volatility. In such dynamic environment, users do not have the exact information about available resources. Queries are based on partial information. This mandates the search mechanism to be emphflexible. On the other hand, the search mechanism is required to be bandwidth emphefficient to support large networks. Variety of search techniques have been proposed to provide satisfactory solution to the conflicting requirements of search efficiency and flexibility. This chapter highlights the search requirements in large scale distributed systems and the ability of the existing distributed search techniques in satisfying these requirements. Representative search techniques from three application domains, namely, P2P content sharing, service discovery and distributed XML databases, are considered. An abstract problem formulation called Distributed Pattern Matching (DPM) is presented as well. The DPM framework can be used as a common ground for addressing the search problem in these three application domains.

Ahmed, Reaz; Boutaba, Raouf

32

Visual Search Elicits the Electrophysiological Marker of Visual Working Memory  

PubMed Central

Background Although limited in capacity, visual working memory (VWM) plays an important role in many aspects of visually-guided behavior. Recent experiments have demonstrated an electrophysiological marker of VWM encoding and maintenance, the contralateral delay activity (CDA), which has been shown in multiple tasks that have both explicit and implicit memory demands. Here, we investigate whether the CDA is evident during visual search, a thoroughly-researched task that is a hallmark of visual attention but has no explicit memory requirements. Methodology/Principal Findings The results demonstrate that the CDA is present during a lateralized search task, and that it is similar in amplitude to the CDA observed in a change-detection task, but peaks slightly later. The changes in CDA amplitude during search were strongly correlated with VWM capacity, as well as with search efficiency. These results were paralleled by behavioral findings showing a strong correlation between VWM capacity and search efficiency. Conclusions/Significance We conclude that the activity observed during visual search was generated by the same neural resources that subserve VWM, and that this activity reflects the maintenance of previously searched distractors.

Emrich, Stephen M.; Al-Aidroos, Naseem; Pratt, Jay; Ferber, Susanne

2009-01-01

33

Serial Deployment of Attention During Visual Search  

Microsoft Academic Search

This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item

Geoffrey F. Woodman; Steven J. Luck

2003-01-01

34

Visual Tracking Using Harmony Search  

Microsoft Academic Search

In this chapter we present a novel method for tracking an arbitrary target through a video sequence using the Harmony Search\\u000a algorithm called the Harmony Filter. The Harmony Filter models the target using a color histogram and compares potential matches\\u000a in each video frame using the Bhattacharyya coefficient. Matches are found using the Improved Harmony Search (IHS) algorithm.\\u000a Experimental results

Jaco Fourie; Steven Mills; Richard Green

2010-01-01

35

Conditional probability modulates visual search efficiency  

PubMed Central

We investigated the effects of probability on visual search. Previous work has shown that people can utilize spatial and sequential probability information to improve target detection. We hypothesized that performance improvements from probability information would extend to the efficiency of visual search. Our task was a simple visual search in which the target was always present among a field of distractors, and could take one of two colors. The absolute probability of the target being either color was 0.5; however, the conditional probability—the likelihood of a particular color given a particular combination of two cues—varied from 0.1 to 0.9. We found that participants searched more efficiently for high conditional probability targets and less efficiently for low conditional probability targets, but only when they were explicitly informed of the probability relationship between cues and target color.

Cort, Bryan; Anderson, Britt

2013-01-01

36

PATTERN SEARCH ALGORITHMS FOR BOUND CONSTRAINED MINIMIZATION  

Microsoft Academic Search

We present a convergence theory for pattern search methods for solving bound constrained nonlinear programs. The analysis relies on the abstract structure of pattern search methods and an understanding of how the pattern interacts with the bound constraints. This analysis makes it possible to develop pattern search methods for bound constrained problems while only slightly restricting the flexibility present in

ROBERT MICHAEL LEWIS; VIRGINIA TORCZON

37

Features in visual search combine linearly.  

PubMed

Single features such as line orientation and length are known to guide visual search, but relatively little is known about how multiple features combine in search. To address this question, we investigated how search for targets differing in multiple features (intensity, length, orientation) from the distracters is related to searches for targets differing in each of the individual features. We tested race models (based on reaction times) and co-activation models (based on reciprocal of reaction times) for their ability to predict multiple feature searches. Multiple feature searches were best accounted for by a co-activation model in which feature information combined linearly (r = 0.95). This result agrees with the classic finding that these features are separable i.e., subjective dissimilarity ratings sum linearly. We then replicated the classical finding that the length and width of a rectangle are integral features-in other words, they combine nonlinearly in visual search. However, to our surprise, upon including aspect ratio as an additional feature, length and width combined linearly and this model outperformed all other models. Thus, length and width of a rectangle became separable when considered together with aspect ratio. This finding predicts that searches involving shapes with identical aspect ratio should be more difficult than searches where shapes differ in aspect ratio. We confirmed this prediction on a variety of shapes. We conclude that features in visual search co-activate linearly and demonstrate for the first time that aspect ratio is a novel feature that guides visual search. PMID:24715328

Pramod, R T; Arun, S P

2014-01-01

38

Visual exploration pattern in hemineglect.  

PubMed

The analysis of eye movement parameters in visual neglect such as cumulative fixation duration, saccade amplitude, or the numbers of saccades has been used to probe attention deficits in neglect patients, since the pattern of exploratory eye movements has been taken as a strong index of attention distribution. The current overview of the literature of visual neglect has its emphasis on studies dealing with eye movement and exploration analysis. We present our own results in 15 neglect patients. The free exploration behavior was analyzed in these patients presenting 32 naturalistic color photographs of everyday scenes. Cumulative fixation duration, spatial distribution of fixations in the horizontal and vertical plane, the number and amplitude of exploratory saccades was analyzed and compared with the results of an age-matched control group. A main result of our study was that in neglect patients, fixation distribution of free exploration of natural scenes is not only influenced by the left-right bias in the horizontal direction but also by the vertical direction. PMID:19084997

Müri, René M; Cazzoli, D; Nyffeler, T; Pflugshaupt, T

2009-03-01

39

Pattern Search Algorithms for Bound Constrained Minimization  

NASA Technical Reports Server (NTRS)

We present a convergence theory for pattern search methods for solving bound constrained nonlinear programs. The analysis relies on the abstract structure of pattern search methods and an understanding of how the pattern interacts with the bound constraints. This analysis makes it possible to develop pattern search methods for bound constrained problems while only slightly restricting the flexibility present in pattern search methods for unconstrained problems. We prove global convergence despite the fact that pattern search methods do not have explicit information concerning the gradient and its projection onto the feasible region and consequently are unable to enforce explicitly a notion of sufficient feasible decrease.

Lewis, Robert Michael; Torczon, Virginia

1996-01-01

40

Exploring metacognitive accuracy in visual search.  

PubMed

For decades, researchers have examined visual search. Much of this work has focused on the factors (e.g., movement, set size, luminance, distractor features and proximity) that influence search speed. However, no research has explored whether people are aware of the influence of these factors. For instance, increases in set size will typically slow down target detection; yet no research has measured participants' metacognitive awareness of this phenomenon. The present research explores this area by integrating a visual search task with a metacognitive monitoring paradigm. All of the explored factors influenced search latency. However, all of the factors except target presence influenced ratings. Saliency and suppression are discussed as two possible explanations for the results. Future directions for extending the theory and the practical benefits of this research are also outlined. PMID:21732205

Redford, Joshua S; Green, Sean; Geer, Micah; Humphrey, Michael; Thiede, Keith W

2011-11-01

41

Graphical Representations of Electronic Search Patterns.  

ERIC Educational Resources Information Center

Discussion of search behavior in electronic environments focuses on the development of GRIP (Graphic Representor of Interaction Patterns), a graphing tool based on HyperCard that produces graphic representations of search patterns. Search state spaces are explained, and forms of data available from electronic searches are described. (34…

Lin, Xia; And Others

1991-01-01

42

Pattern Search Methods for Linearly Constrained Minimization  

Microsoft Academic Search

We extend pattern search methods to linearly constrained minimization. We develop a general class of feasible point pattern search algorithms and prove global convergence to a Karush-Kuhn- Tucker point. As in the case of unconstrained minimization, pattern search methods for linearly constrained problems accomplish this without explicit recourse to the gradient or the directional derivative. Key to the analysis of

Robert Michael Lewis; Virginia Torczon

2000-01-01

43

Dynamic Prototypicality Effects in Visual Search  

ERIC Educational Resources Information Center

In recent studies, researchers have discovered a larger neural activation for stimuli that are more extreme exemplars of their stimulus class, compared with stimuli that are more prototypical. This has been shown for faces as well as for familiar and novel shape classes. We used a visual search task to look for a behavioral correlate of these…

Kayaert, Greet; Op de Beeck, Hans P.; Wagemans, Johan

2011-01-01

44

Optimal eye movement strategies in visual search.  

PubMed

To perform visual search, humans, like many mammals, encode a large field of view with retinas having variable spatial resolution, and then use high-speed eye movements to direct the highest-resolution region, the fovea, towards potential target locations. Good search performance is essential for survival, and hence mammals may have evolved efficient strategies for selecting fixation locations. Here we address two questions: what are the optimal eye movement strategies for a foveated visual system faced with the problem of finding a target in a cluttered environment, and do humans employ optimal eye movement strategies during a search? We derive the ideal bayesian observer for search tasks in which a target is embedded at an unknown location within a random background that has the spectral characteristics of natural scenes. Our ideal searcher uses precise knowledge about the statistics of the scenes in which the target is embedded, and about its own visual system, to make eye movements that gain the most information about target location. We find that humans achieve nearly optimal search performance, even though humans integrate information poorly across fixations. Analysis of the ideal searcher reveals that there is little benefit from perfect integration across fixations--much more important is efficient processing of information on each fixation. Apparently, evolution has exploited this fact to achieve efficient eye movement strategies with minimal neural resources devoted to memory. PMID:15772663

Najemnik, Jiri; Geisler, Wilson S

2005-03-17

45

Investigation of Neural Strategies of Visual Search  

NASA Technical Reports Server (NTRS)

The goal of this project was to measure how neurons in the superior colliculus (SC) change their activity during a visual search task. Specifically, we proposed to measure how the activity of these neurons was altered by the discriminability of visual targets and to test how these changes might predict the changes in the subjects performance. The primary rationale for this study was that understanding how the information encoded by these neurons constrains overall search performance would foster the development of better models of human performance. Work performed during the period supported by this grant has achieved these aims. First, we have recorded from neurons in the superior colliculus (SC) during a visual search task in which the difficulty of the task and the performance of the subject was systematically varied. The results from these single-neuron physiology experiments shows that prior to eye movement onset, the difference in activity across the ensemble of neurons reaches a fixed threshold value, reflecting the operation of a winner-take-all mechanism. Second, we have developed a model of eye movement decisions based on the principle of winner-take-all . The model incorporates the idea that the overt saccade choice reflects only one of the multiple saccades prepared during visual discrimination, consistent with our physiological data. The value of the model is that, unlike previous models, it is able to account for both the latency and the percent correct of saccade choices.

Krauzlis, Richard J.

2003-01-01

46

Do Multielement Visual Tracking and Visual Search Draw Continuously on the Same Visual Attention Resources?  

ERIC Educational Resources Information Center

Multielement visual tracking and visual search are 2 tasks that are held to require visual-spatial attention. The authors used the attentional operating characteristic (AOC) method to determine whether both tasks draw continuously on the same attentional resource (i.e., whether the 2 tasks are mutually exclusive). The authors found that observers…

Alvarez, George A.; Horowitz, Todd S.; Arsenio, Helga C.; DiMase, Jennifer S.; Wolfe, Jeremy M.

2005-01-01

47

Coarse guidance by numerosity in visual search  

PubMed Central

In five experiments, we examined whether the number of items can guide visual focal attention. Observers searched for the target area with the largest (or smallest) number of dots (squares in Experiment 4 and “checkerboards” in Experiment 5) among distractor areas with a smaller (or larger) number of dots. Results of Experiments 1 and 2 show that search efficiency is determined by target to distractor dot ratios. In searches where target items contained more dots than did distractor items, ratios over 1.5:1 yielded efficient search. Searches for targets where target items contained fewer dots than distractor items were harder. Here, ratios needed to be lower than 1:2 to yield efficient search. When the areas of the dots and of the squares containing them were fixed, as they were in Experiments 1 and 2, dot density and total dot area increased as dot number increased. Experiment 3 removed the density and area cues by allowing dot size and total dot area to vary. This produced a marked decline in search performance. Efficient search now required ratios of above 3:1 or below 1:3. By using more realistic and isoluminant stimuli, Experiments 4 and 5 show that guidance by numerosity is fragile. As is found with other features that guide focal attention (e.g., color, orientation, size), the numerosity differences that are able to guide attention by bottom-up signals are much coarser than the differences that can be detected in attended stimuli.

Reijnen, Ester; Wolfe, Jeremy M.; Krummenacher, Joseph

2014-01-01

48

Personalized online information search and visualization  

PubMed Central

Background The rapid growth of online publications such as the Medline and other sources raises the questions how to get the relevant information efficiently. It is important, for a bench scientist, e.g., to monitor related publications constantly. It is also important, for a clinician, e.g., to access the patient records anywhere and anytime. Although time-consuming, this kind of searching procedure is usually similar and simple. Likely, it involves a search engine and a visualization interface. Different words or combination reflects different research topics. The objective of this study is to automate this tedious procedure by recording those words/terms in a database and online sources, and use the information for an automated search and retrieval. The retrieved information will be available anytime and anywhere through a secure web server. Results We developed such a database that stored searching terms, journals and et al., and implement a piece of software for searching the medical subject heading-indexed sources such as the Medline and other online sources automatically. The returned information were stored locally, as is, on a server and visible through a Web-based interface. The search was performed daily or otherwise scheduled and the users logon to the website anytime without typing any words. The system has potentials to retrieve similarly from non-medical subject heading-indexed literature or a privileged information source such as a clinical information system. The issues such as security, presentation and visualization of the retrieved information were thus addressed. One of the presentation issues such as wireless access was also experimented. A user survey showed that the personalized online searches saved time and increased and relevancy. Handheld devices could also be used to access the stored information but less satisfactory. Conclusion The Web-searching software or similar system has potential to be an efficient tool for both bench scientists and clinicians for their daily information needs.

Chen, Dongquan; Orthner, Helmuth F; Sell, Susan M

2005-01-01

49

Pattern formation in the developing visual cortex  

NASA Astrophysics Data System (ADS)

In the visual cortex of the brain, neurons specialized to process particular aspects of the visual input are arranged in complex spatial patterns, called cortical maps, and interact through a dense network of intracortical connections. Many experimental results are consistent with the hypothesis that the precise organization of patterns and connections within the cortex is not predetermined by genetic instructions, but emerges through activity-dependent self-organization during the first months of life. In this chapter, we will first survey the layout of visual cortical maps and the structure of intracortical connections, and then discuss their activity-dependent development. In the subsequent sections of the chapter, we will discuss the formation of patterns in the developing visual cortex from a nonlinear dynamics perspective. In particular, we will analyze the instability mechanisms, through which cortical patterns presumably emerge early in development. We will also discuss the intriguing possibility that cortical patterns undergo substantial rearrangement during the first months of life.

Löwel, Siegrid; Wolf, Fred

50

Visual Templates in Pattern Generalization Activity  

ERIC Educational Resources Information Center

In this research article, I present evidence of the existence of visual templates in pattern generalization activity. Such templates initially emerged from a 3-week design-driven classroom teaching experiment on pattern generalization involving linear figural patterns and were assessed for existence in a clinical interview that was conducted four…

Rivera, F. D.

2010-01-01

51

Pattern Search Methods for Linearly Constrained Minimization  

NASA Technical Reports Server (NTRS)

We extend pattern search methods to linearly constrained minimization. We develop a general class of feasible point pattern search algorithms and prove global convergence to a Karush-Kuhn-Tucker point. As in the case of unconstrained minimization, pattern search methods for linearly constrained problems accomplish this without explicit recourse to the gradient or the directional derivative. Key to the analysis of the algorithms is the way in which the local search patterns conform to the geometry of the boundary of the feasible region.

Lewis, Robert Michael; Torczon, Virginia

1998-01-01

52

On the Local Convergence of Pattern Search  

NASA Technical Reports Server (NTRS)

We examine the local convergence properties of pattern search methods, complementing the previously established global convergence properties for this class of algorithms. We show that the step-length control parameter which appears in the definition of pattern search algorithms provides a reliable asymptotic measure of first-order stationarity. This gives an analytical justification for a traditional stopping criterion for pattern search methods. Using this measure of first-order stationarity, we analyze the behavior of pattern search in the neighborhood of an isolated local minimizer. We show that a recognizable subsequence converges r-linearly to the minimizer.

Dolan, Elizabeth D.; Lewis, Robert Michael; Torczon, Virginia; Bushnell, Dennis M. (Technical Monitor)

2000-01-01

53

An active visual search interface for Medline.  

PubMed

Searching the Medline database is almost a daily necessity for many biomedical researchers. However, available Medline search solutions are mainly designed for the quick retrieval of a small set of most relevant documents. Because of this search model, they are not suitable for the large-scale exploration of literature and the underlying biomedical conceptual relationships, which are common tasks in the age of high throughput experimental data analysis and cross-discipline research. We try to develop a new Medline exploration approach by incorporating interactive visualization together with powerful grouping, summary, sorting and active external content retrieval functions. Our solution, PubViz, is based on the FLEX platform designed for interactive web applications and its prototype is publicly available at: http://brainarray.mbni.med.umich.edu/Brainarray/DataMining/PubViz. PMID:17951838

Xuan, Weijian; Dai, Manhong; Mirel, Barbara; Wilson, Justin; Athey, Brian; Watson, Stanley J; Meng, Fan

2007-01-01

54

Guided Text Search Using Adaptive Visual Analytics  

SciTech Connect

This research demonstrates the promise of augmenting interactive visualizations with semi- supervised machine learning techniques to improve the discovery of significant associations and insights in the search and analysis of textual information. More specifically, we have developed a system called Gryffin that hosts a unique collection of techniques that facilitate individualized investigative search pertaining to an ever-changing set of analytical questions over an indexed collection of open-source documents related to critical national infrastructure. The Gryffin client hosts dynamic displays of the search results via focus+context record listings, temporal timelines, term-frequency views, and multiple coordinate views. Furthermore, as the analyst interacts with the display, the interactions are recorded and used to label the search records. These labeled records are then used to drive semi-supervised machine learning algorithms that re-rank the unlabeled search records such that potentially relevant records are moved to the top of the record listing. Gryffin is described in the context of the daily tasks encountered at the US Department of Homeland Security s Fusion Center, with whom we are collaborating in its development. The resulting system is capable of addressing the analysts information overload that can be directly attributed to the deluge of information that must be addressed in the search and investigative analysis of textual information.

Steed, Chad A [ORNL; Symons, Christopher T [ORNL; Senter, James K [ORNL; DeNap, Frank A [ORNL

2012-10-01

55

Visual Search for Safety Colors under Low Illuminance Conditions  

Microsoft Academic Search

This study aims to examine the search efficiency under low illuminance conditions for three safety colors; red, orange and yellow, which are used for danger and caution signs. They are subjected to a visual search task. Images of visual stimuli consisting of an array of colored circles placed on a large visual field (a visual angle of 40 deg.) were

Nobuhisa OCHIAI; Masako SATO

56

Visual search in spatial neglect studied with a preview paradigm  

PubMed Central

Impaired visual search is a hallmark of spatial neglect. When searching for an unique feature (e.g., color) neglect patients often show only slight visual field asymmetries. In contrast, when the target is defined by a combination of features (e.g., color and form) they exhibit a severe deficit of contralesional search. This finding suggests a selective impairment of the serial deployment of spatial attention. Here, we examined this deficit with a preview paradigm. Neglect patients searched for a target defined by the conjunction of shape and color, presented together with varying numbers of distracters. The presentation time was varied such that on some trials participants previewed the target together with same-shape/different-color distracters, for 300 or 600 ms prior to the appearance of additional different-shape/same-color distracters. On the remaining trials the target and all distracters were shown simultaneously. Healthy participants exhibited a serial search strategy only when all items were presented simultaneously, whereas in both preview conditions a pop-out effect was observed. Neglect patients showed a similar pattern when the target was presented in the right hemifield. In contrast, when searching for a target in the left hemifield they showed serial search in the no-preview condition, as well as with a preview of 300 ms, and partly even at 600 ms. A control experiment suggested that the failure to fully benefit from item preview was probably independent of accurate perception of time. Our results, when viewed in the context of existing literature, lead us to conclude that the visual search deficit in neglect reflects two additive factors: a biased representation of attentional priority in favor of ipsilesional information and exaggerated capture of attention by ipsilesional abrupt onsets.

Fellrath, Julia; Blanche-Durbec, Vanessa; Schnider, Armin; Jacquemoud, Anne-Sophie; Ptak, Radek

2012-01-01

57

Reader error, object recognition, and visual search  

NASA Astrophysics Data System (ADS)

Small abnormalities such as hairline fractures, lung nodules and breast tumors are missed by competent radiologists with sufficient frequency to make them a matter of concern to the medical community; not only because they lead to litigation but also because they delay patient care. It is very easy to attribute misses to incompetence or inattention. To do so may be placing an unjustified stigma on the radiologists involved and may allow other radiologists to continue a false optimism that it can never happen to them. This review presents some of the fundamentals of visual system function that are relevant to understanding the search for and the recognition of small targets embedded in complicated but meaningful backgrounds like chests and mammograms. It presents a model for visual search that postulates a pre-attentive global analysis of the retinal image followed by foveal checking fixations and eventually discovery scanning. The model will be used to differentiate errors of search, recognition and decision making. The implications for computer aided diagnosis and for functional workstation design are discussed.

Kundel, Harold L.

2004-05-01

58

Visual Field Screening System by Using Overlapped Fixation Patterns  

NASA Astrophysics Data System (ADS)

This study introduces a novel technique for estimating visual field by using overlapped fixation patterns obtained by amounts of displacement in voluntary eye movements during searching-tracking trials, as an alternative screening medical device for visual field examination. Proposed system was evaluated by glaucoma patients, in order to study whether or not the proposed system can be used as a visual field detection device for screening. As a result, the proposed system detected the visual field abnormality to a certain extent. However, there were some cases that detection of Mariotte blind spots was inaccurately performed. The experimental results revealed that there was room to reconsider our understanding regarding the effect of ptosis, overlapped with eye sight as well as calibration of the display position to the correct location to be examined. Results of the evaluation experiment indicated that this proposed system has a potential to be used as a visual field examination device for screening.

Kotani, Kentaro; Yoshikawa, Ryota; Tamura, Toshiki; Asao, Takafumi; Sugiyama, Tetsuya; Ueki, Mari; Kojima, Shota; Shibata, Maho; Ikeda, Tsunehiko

59

Innate visual learning through spontaneous activity patterns.  

PubMed

Patterns of spontaneous activity in the developing retina, LGN, and cortex are necessary for the proper development of visual cortex. With these patterns intact, the primary visual cortices of many newborn animals develop properties similar to those of the adult cortex but without the training benefit of visual experience. Previous models have demonstrated how V1 responses can be initialized through mechanisms specific to development and prior to visual experience, such as using axonal guidance cues or relying on simple, pairwise correlations on spontaneous activity with additional developmental constraints. We argue that these spontaneous patterns may be better understood as part of an "innate learning" strategy, which learns similarly on activity both before and during visual experience. With an abstraction of spontaneous activity models, we show how the visual system may be able to bootstrap an efficient code for its natural environment prior to external visual experience, and we continue the same refinement strategy upon natural experience. The patterns are generated through simple, local interactions and contain the same relevant statistical properties of retinal waves and hypothesized waves in the LGN and V1. An efficient encoding of these patterns resembles a sparse coding of natural images by producing neurons with localized, oriented, bandpass structure-the same code found in early visual cortical cells. We address the relevance of higher-order statistical properties of spontaneous activity, how this relates to a system that may adapt similarly on activity prior to and during natural experience, and how these concepts ultimately relate to an efficient coding of our natural world. PMID:18670593

Albert, Mark V; Schnabel, Adam; Field, David J

2008-01-01

60

Visual search from lab to clinic and back  

NASA Astrophysics Data System (ADS)

Many of the tasks of medical image perception can be understood as demanding visual search tasks (especially if you happen to be a visual search researcher). Basic research on visual search can tell us quite a lot about how medical image search tasks proceed because even experts have to use the human "search engine" with all its limitations. Humans can only deploy attention to one or a very few items at any one time. Human search is "guided" search. Humans deploy their attention to likely target objects on the basis of the basic visual features of object and on the basis of an understanding of the scene containing those objects. This guidance operates in medical images as well as in the mundane scenes of everyday life. The paper reviews some of the dialogue between medical image perception by experts and visual search as studied in the laboratory.

Wolfe, Jeremy M.

2014-03-01

61

A Visual Interface for Multivariate Temporal Data: Finding Patterns of Events across Multiple Histories  

Microsoft Academic Search

Finding patterns of events over time is important in searching patient histories, web logs, news stories, and criminal activities. This paper presents PatternFinder, an integrated interface for query and result-set visualization for search and discovery of temporal patterns within multivariate and categorical data sets. We define temporal patterns as sequences of events with inter- event time spans. PatternFinder allows users

Jerry Alan Fails; Amy K. Karlson; Layla Shahamat; Ben Shneiderman

2006-01-01

62

Electrophysiological measurement of rapid shifts of attention during visual search  

Microsoft Academic Search

1 . Vision researchers have captured this attribute of real-world perception in the laboratory by using visual search tasks, in which subjects search for a target object in arrays containing varying numbers of non-target distractor objects. Under many conditions, the amount of time required to detect a visual search target increases as the number of objects in the stimulus array

Geoffrey F. Woodman; Steven J. Luck

1999-01-01

63

Temporal aspects of visual search studied by transcranial magnetic stimulation  

Microsoft Academic Search

Transcranial magnetic stimulation was applied over the parietal visual cortex of subjects while they were performing ‘popout’ or conjunction visual search tasks in arrays containing eight distractors. Magnetic stimulation had no detrimental effect on the performance of pop-out search, but did significantly increase reaction times on conjunction search when stimulation was applied over the right parietal cortex 100 msec after

Elisabeth Ashbridge; Vincent Walsh; Alan Cowey

1997-01-01

64

Spoken Language Comprehension Improves the Efficiency of Visual Search  

Microsoft Academic Search

Much recent eye-tracking research has demonstrated that visual perception plays an integral part in on-line spoken language comprehension, in environments that closely mimic our normal interaction with our physical environment and other humans. To test for the inverse, an influence of language on visual processing, we modified the standard visual search task by introducing spoken linguistic input. In classic visual

Melinda J. Tyler

65

Racial Differences in Job Search Patterns.  

National Technical Information Service (NTIS)

The study covers patterns of job search with respect to race by surveying a sample of male labor force participants in Raleigh in 1967. It was desired to know if race and methods of job search were independent of one another, and whether nonwhites and whi...

W. V. Pace

1967-01-01

66

Brain Activations during Visual Search: Contributions of Search Efficiency versus Feature Binding  

Microsoft Academic Search

We investigated the involvement of the parietal cortex in binding features during visual search using functional magnetic resonance imaging. We tested 10 subjects in four visual search tasks across which we independently manipulated (1) the requirement to integrate different types of features in a stimulus (feature or conjunction search) and (2) the degree of search efficiency (efficient or inefficient). We

A. C. Nobre; J. T. Coull; V. Walsh; C. D. Frith

2003-01-01

67

Visual search is slowed when visuospatial working memory is occupied  

Microsoft Academic Search

Visual working memory plays a central role in most models of visual search. However, a recent study showed that search efficiency\\u000a was not impaired when working memory was filled to capacity by a concurrent object memory task (Woodman, Vogel, & Luck, 2001).\\u000a Objects and locations may be stored in separate working memory subsystems, and it is plausible that visual search

Geoffrey F. Woodman; Steven J. Luck

2004-01-01

68

Visual search behaviour during laparoscopic cadaveric procedures  

NASA Astrophysics Data System (ADS)

Laparoscopic surgery provides a very complex example of medical image interpretation. The task entails: visually examining a display that portrays the laparoscopic procedure from a varying viewpoint; eye-hand coordination; complex 3D interpretation of the 2D display imagery; efficient and safe usage of appropriate surgical tools, as well as other factors. Training in laparoscopic surgery typically entails practice using surgical simulators. Another approach is to use cadavers. Viewing previously recorded laparoscopic operations is also a viable additional approach and to examine this a study was undertaken to determine what differences exist between where surgeons look during actual operations and where they look when simply viewing the same pre-recorded operations. It was hypothesised that there would be differences related to the different experimental conditions; however the relative nature of such differences was unknown. The visual search behaviour of two experienced surgeons was recorded as they performed three types of laparoscopic operations on a cadaver. The operations were also digitally recorded. Subsequently they viewed the recording of their operations, again whilst their eye movements were monitored. Differences were found in various eye movement parameters when the two surgeons performed the operations and where they looked when they simply watched the recordings of the operations. It is argued that this reflects the different perceptual motor skills pertinent to the different situations. The relevance of this for surgical training is explored.

Dong, Leng; Chen, Yan; Gale, Alastair G.; Rees, Benjamin; Maxwell-Armstrong, Charles

2014-03-01

69

SOME TEMPORAL CHARACTERISTICS OF VISUAL PATTERN PERCEPTION  

Microsoft Academic Search

VISUAL STIMULI WERE CONSTRUCTED SO THAT ANY GIVEN STIMULUS BY ITSELF APPEARED TO BE A RANDOM COLLECTION OF DOTS. HOWEVER, WHEN 2 CORRESPONDING STIMULI WERE SUPERIMPOSED BY MEANS OF A 2-FIELD TACHISTOSCOPE, A 3-LETTER NONSENSE SYLLABLE WAS PERCEIVED. TEMPORAL ORGANIZATION IN PERCEPTION WAS STUDIED IN EXP. I BY VARYING THE INTERVAL BETWEEN THE PRESENTATION OF THE 2 CORRESPONDING PATTERNS OVER

CHARLES W. ERIKSEN; JAMES F. COLLINS

1967-01-01

70

Fraction Patterns--Visual and Numerical.  

ERIC Educational Resources Information Center

A visual model of fractions, the tower of bars, is used to discover patterns. Examples include equalities, inequalities, sums of unit fractions, sums of differences, symmetry, and differences and products. Infinite sequences of numbers, infinite series, and concepts of limits can be introduced. (DC)

Bennett, Albert B., Jr.

1989-01-01

71

Recognition of Facially Expressed Emotions and Visual Search Strategies in Adults with Asperger Syndrome  

ERIC Educational Resources Information Center

Can the disadvantages persons with Asperger syndrome frequently experience with reading facially expressed emotions be attributed to a different visual perception, affecting their scanning patterns? Visual search strategies, particularly regarding the importance of information from the eye area, and the ability to recognise facially expressed…

Falkmer, Marita; Bjallmark, Anna; Larsson, Matilda; Falkmer, Torbjorn

2011-01-01

72

Quantum Pattern Search with Closed Match  

NASA Astrophysics Data System (ADS)

This paper we proposed a quantum pattern search algorithm based on Grover’s algorithm with closed match. Compared to QuAM proposed by Dan Ventura and QuAM with distributed queries proposed by Ezhov, our algorithm could not only resolve completion problem but also retrieved the full information of the query pattern which only known partial information with non-negligible probability. The algorithm took advantage of the encoding for the pattern set. Moreover we transformed the encoding of each pattern in set to encode all the pattern match cases in order to reduce the cost of encoding. Thus, the nontrivial initial state brought a new method to realize quantum pattern search with a series of proper unitary operations. The simulation result of experiments was also proved that our algorithm was useful and efficient.

Zhou, Ri-Gui; Shen, Chen-Yi; Xiao, Tian-ru; Li, Yan-cheng

2013-11-01

73

Visual abstraction of complex motion patterns  

NASA Astrophysics Data System (ADS)

Today's tracking devices allow high spatial and temporal resolutions and due to their decreasing size also an ever increasing number of application scenarios. However, understanding motion over time is quite difficult as soon as the resulting trajectories are getting complex. Simply plotting the data may obscure important patterns since trajectories over long time periods often include many revisits of the same place which creates a high degree of over-plotting. Furthermore, important details are often hidden due to a combination of large-scale transitions with local and small-scale movement patterns. We present a visualization and abstraction technique for such complex motion data. By analyzing the motion patterns and displaying them with visual abstraction techniques a synergy of aggregation and simplification is reached. The capabilities of the method are shown in real-world applications for tracked animals and discussed with experts from biology. Our proposed abstraction techniques reduce visual clutter and help analysts to understand the movement patterns that are hidden in raw spatiotemporal data.

Janetzko, Halldór; Jäckle, Dominik; Deussen, Oliver; Keim, Daniel A.

2013-12-01

74

Visually controlled matching of pattern movement.  

PubMed

Subjects were asked to match the speeds of two moving random-dot patterns seen through circular apertures. The speed of one pattern that moved horizontally toward the right of a computer screen changed continuously. The speed of this pattern represented the target. It was to be matched with the speed of the second pattern, which moved in the opposite direction. The subject controlled the speed of the second pattern by means of an isometric joystick. The distance between the apertures on the screen as well as the subject's distance from the screen served as experimental parameters. In this way, the effects of both spatial and temporal transients of pattern speed on human tracking performance were studied. To avoid anticipation by the subject, the amplitude and the frequency of the target pattern speed changed pseudorandomly. The accuracy with which the subject performed the matching task was influenced by the mean pattern speed and the parameters of the visual field. Within lower velocity ranges, the subject's sensitivity to the instantaneous speed differences varied according to Weber's law. The cross-correlation of the velocity time courses decreased when the mean speed of the target pattern was increased. Two stimulus parameters had a strong influence on the modulation of the correlation value: (1) the angular size of the stimulus on the retina and (2) the retinal eccentricity of the stimulus. PMID:1620569

Wüst, R; Kappers, A M; Koenderink, J J

1992-06-01

75

Guided Visual Search in Individuals with Mental Retardation.  

ERIC Educational Resources Information Center

A study investigated the ability of six individuals with mental retardation to focus on task-relevant elements of complex visual arrays and increased visual-search efficiency. Results found participants were able to limit attention to the task-relevant items on a guided search task, thus greatly reducing overall target identification times.…

Carlin, Michael T.; Soraci, Sal A.; Dennis, Nancy A.; Strawbridge, Christina; Chechile, Nicholas A.

2002-01-01

76

Spatiotemporal Segregation in Visual Search: Evidence from Parietal Lesions  

ERIC Educational Resources Information Center

The mechanisms underlying segmentation and selection of visual stimuli over time were investigated in patients with posterior parietal damage. In a modified visual search task, a preview of old objects preceded search of a new set for a target while the old items remained. In Experiment 1, control participants ignored old and prioritized new…

Olivers, Christian N. L.; Humphreys, Glyn W.

2004-01-01

77

RANK ORDERING AND POSITIVE BASES IN PATTERN SEARCH ALGORITHMS  

Microsoft Academic Search

We present two new classes of pattern search algorithms for unconstrained mini- mization: the rank ordered and the positive basis pattern search methods. These algorithms can nearly halve the worst case cost of an iteration compared to the classical pattern search algorithms. The rank ordered pattern search methods are based on a heuristic for approximating the direction of steepest descent,

ROBERT MICHAEL LEWIS; VIRGINIA TORCZON

1998-01-01

78

Usage patterns of an online search system  

Microsoft Academic Search

This article examines the usage patterns of the ELHILL retrieval program of the National Library of Medicine's MEDLARS systeni. Based on a sample of 6759 searches, the study anaiyzes the frequency of various commands and command options, classifies messages issued by the system, and investigates searcher error rates. The ar- ticle conciudes with suggestions for improving and redesigning both the

Michael D. Cooper

1983-01-01

79

Searching for intellectual turning points: Progressive knowledge domain visualization  

PubMed Central

This article introduces a previously undescribed method progressively visualizing the evolution of a knowledge domain's cocitation network. The method first derives a sequence of cocitation networks from a series of equal-length time interval slices. These time-registered networks are merged and visualized in a panoramic view in such a way that intellectually significant articles can be identified based on their visually salient features. The method is applied to a cocitation study of the superstring field in theoretical physics. The study focuses on the search of articles that triggered two superstring revolutions. Visually salient nodes in the panoramic view are identified, and the nature of their intellectual contributions is validated by leading scientists in the field. The analysis has demonstrated that a search for intellectual turning points can be narrowed down to visually salient nodes in the visualized network. The method provides a promising way to simplify otherwise cognitively demanding tasks to a search for landmarks, pivots, and hubs.

Chen, Chaomei

2004-01-01

80

How might the rules that govern visual search constrain the design of visual displays?  

Microsoft Academic Search

In visual search attention can be guided toward a target item among distracting items by a limited set of basic features. This talk will summarize the rules of effective guidance (e.g. you can efficiently guide attention toward a red and vertical item but not a red and green item). Humans are good at searching for things in a crowded visual

Jeremy M Wolfe

81

Visual Search Demands Dictate Reliance on Working Memory Storage  

PubMed Central

Previous research suggested that working memory (WM) does not play any significant role in visual search. In three experiments, we investigated the search difficulty and individual differences in WM capacity as determinants of WM involvement during visual search tasks, using both behavioral and electrophysiological markers [i.e., the contralateral delay activity (CDA), which is a marker for WM capacity allocation]. Human participants performed a visual search task that contained a target, neutral distractors, and a flanker distractor. Overall, we found that, as the search difficultly increased (as indicated by longer reaction times), so did the role of WM in performing the search task (as indicated by larger CDA amplitudes). Moreover, the results pinpoint a dissociation between the two types of factors that determined the WM involvement in the search process. Namely, individual differences in WM capacity and search difficulty independently affected the degree to which the search process relied on WM. Instead of showing a progressive role, individual differences in WM capacity correlated with the search efficiency in all search conditions (i.e., easy, medium, and difficult). Counterintuitively, individuals with high WM capacity generally relied less on WM during the search task.

Vogel, Edward K.

2011-01-01

82

Advances in Modeling Visual Search and Target Discrimination Performance.  

National Technical Information Service (NTIS)

This paper reports on advances in mathematical models of observer- ensemble performance in narrow-field- of-view visual search and target discrimination for ground vehicles in natural terrain. Three developments are presented. We show that the distributio...

D. J. Gorsich G. Witus G. R. Gerhart R. E. Karlsen

2002-01-01

83

The minimum principle and visual pattern completion.  

PubMed

The minimum principle states that a perceiver will see the simplest possible interpretation of a pattern. Some theorists of human perception take this principle as a core-explanatory concept. Others hold the view that a perceptual minimum principle is untenable. In two recent extensive surveys of the relevant literature a more differentiated position is taken: the minimum principle is not renounced in a definite way. In the research reported here, an intuitively appealing specification of a minimum principle is tested. An experiment on visual pattern completion was performed in which patterns were presented to subjects who traced the contours of the shapes they saw. It was predicted that there would be a preference for interpretations that describe a pattern as a set of separate shapes with minimal information load as computed by Leeuwenberg's coding language. However, only half of the responses given by the subjects were predicted by this specification of a minimum principle. It was further demonstrated that locally complex interpretations of junctions of contour elements are easily made, but not in order to attain globally minimal interpretations. PMID:2608867

Boselie, F; Wouterlood, D

1989-01-01

84

Asynchronous parallel pattern search for nonlinear optimization  

SciTech Connect

Parallel pattern search (PPS) can be quite useful for engineering optimization problems characterized by a small number of variables (say 10--50) and by expensive objective function evaluations such as complex simulations that take from minutes to hours to run. However, PPS, which was originally designed for execution on homogeneous and tightly-coupled parallel machine, is not well suited to the more heterogeneous, loosely-coupled, and even fault-prone parallel systems available today. Specifically, PPS is hindered by synchronization penalties and cannot recover in the event of a failure. The authors introduce a new asynchronous and fault tolerant parallel pattern search (AAPS) method and demonstrate its effectiveness on both simple test problems as well as some engineering optimization problems

P. D. Hough; T. G. Kolda; V. J. Torczon

2000-01-01

85

Common Visual Pattern Discovery via Directed Graph.  

PubMed

A directed graph (or digraph) approach is proposed in this paper for identifying all the visual objects commonly presented in the two images under comparison. As a model, the directed graph is superior to the undirected graph, since there are two link weights with opposite orientations associated with each link of the graph. However, it inevitably draws two main challenges: 1) how to compute the two link weights for each link and 2) how to extract the subgraph from the digraph. For 1), a novel n-ranking process for computing the generalized median and the Gaussian link-weight mapping function are developed that basically map the established undirected graph to the digraph. To achieve this graph mapping, the proposed process and function are applied to each vertex independently for computing its directed link weight by not only considering the influences inserted from its immediately adjacent neighboring vertices (in terms of their link-weight values), but also offering other desirable merits-i.e., link-weight enhancement and computational complexity reduction. For 2), an evolutionary iterative process for solving the non-cooperative game theory is exploited to handle the non-symmetric weighted adjacency matrix. The abovementioned two stages of processes will be conducted for each assumed scale-change factor, experimented over a range of possible values, one factor at a time. If there is a match on the scale-change factor under experiment, the common visual patterns with the same scale-change factor will be extracted. If more than one pattern are extracted, the proposed topological splitting method is able to further differentiate among them provided that the visual objects are sufficiently far apart from each other. Extensive simulation results have clearly demonstrated the superior performance accomplished by the proposed digraph approach, compared with those of using the undirected graph approach. PMID:24723536

Wang, Chen; Ma, Kai-Kuang

2014-03-01

86

Image Search Visualization in a Planetary VO  

NASA Astrophysics Data System (ADS)

A multi-mission image search tool has been created through a collaboration between Google and NASA Ames Research Center, using Google Earth as a virtual observatory (VO) for accessing search results. Follow-on work will expand the utilization of the VO and refine the features based on user research.

Trimble, J.; Rose, M.; Schauer, C.; Russell, D.

2011-10-01

87

Visual Search Asymmetry with Uncertain Targets  

ERIC Educational Resources Information Center

The underlying mechanism of search asymmetry is still unknown. Many computational models postulate top-down selection of target-defining features as a crucial factor. This feature selection account implies, and other theories implicitly assume, that predefined target identity is necessary for search asymmetry. The authors tested the validity of…

Saiki, Jun; Koike, Takahiko; Takahashi, Kohske; Inoue, Tomoko

2005-01-01

88

Conjunctive Visual Search in Individuals with and without Mental Retardation  

ERIC Educational Resources Information Center

A comprehensive understanding of the basic visual and cognitive abilities of individuals with mental retardation is critical for understanding the basis of mental retardation and for the design of remediation programs. We assessed visual search abilities in individuals with mild mental retardation and in MA- and CA-matched comparison groups. Our…

Carlin, Michael; Chrysler, Christina; Sullivan, Kate

2007-01-01

89

Visualizing search results: some alternatives to query-document similarity  

Microsoft Academic Search

A digital library of computer science literature, Envision provides powerful information visualization by displaying search results as a matrix of icons, with layout semantics under user control. Envision's Graphic View interacts with an Item Summary Window giving users access to bibliographic information, and XMosaic provides access to complete bibliographic information, abstracts, and full content. While many visualization interfaces for information

Lucy Terry Nowell; Robert K. France; Deborah Hix; Lenwood S. Heath; Edward A. Fox

1996-01-01

90

Priming of luminance-defined motion direction in visual search  

Microsoft Academic Search

Features that we have recently attended to strongly influence how we allocate visual attention across a subsequently viewed\\u000a visual scene. Here, we investigate the characteristics of any such repetition effects during visual search for Gabor patch\\u000a targets drifting in the odd direction relative to a set of distractors. The results indicate that repetition of motion direction\\u000a has a strong effect

Árni KristjÁnsson; Andri Bjarnason; Árni Bragi Hjaltason; Bryndís Gyda Stefánsdóttir

2009-01-01

91

Priming and the guidance by visual and categorical templates in visual search.  

PubMed

Visual search is thought to be guided by top-down templates that are held in visual working memory. Previous studies have shown that a search-guiding template can be rapidly and strongly implemented from a visual cue, whereas templates are less effective when based on categorical cues. Direct visual priming from cue to target may underlie this difference. In two experiments we first asked observers to remember two possible target colors. A postcue then indicated which of the two would be the relevant color. The task was to locate a briefly presented and masked target of the cued color among irrelevant distractor items. Experiment 1 showed that overall search accuracy improved more rapidly on the basis of a direct visual postcue that carried the target color, compared to a neutral postcue that pointed to the memorized color. However, selectivity toward the target feature, i.e., the extent to which observers searched selectively among items of the cued vs. uncued color, was found to be relatively unaffected by the presence of the visual signal. In Experiment 2 we compared search that was based on either visual or categorical information, but now controlled for direct visual priming. This resulted in no differences in overall performance nor selectivity. Altogether the results suggest that perceptual processing of visual search targets is facilitated by priming from visual cues, whereas attentional selectivity is enhanced by a working memory template that can formed from both visual and categorical input. Furthermore, if the priming is controlled for, categorical- and visual-based templates similarly enhance search guidance. PMID:24605105

Wilschut, Anna; Theeuwes, Jan; Olivers, Christian N L

2014-01-01

92

Effects of Scleral Search Coil Wear on Visual Function  

Microsoft Academic Search

PURPOSE. The scleral search coil is widely regarded as the gold standard measurement technique for eye movements. The ef- fect of wearing scleral search coils on human vision has not been systematically studied. However, there are anecdotal re- ports of degraded visual acuity, mild eye irritation, and an increase rise in intraocular pressure (IOP). The current study was conducted to

Elizabeth L. Irving; James E. Zacher; Robert S. Allison; Murchison G. Callender

2003-01-01

93

Pip and Pop: Nonspatial Auditory Signals Improve Spatial Visual Search  

ERIC Educational Resources Information Center

Searching for an object within a cluttered, continuously changing environment can be a very time-consuming process. The authors show that a simple auditory pip drastically decreases search times for a synchronized visual object that is normally very difficult to find. This effect occurs even though the pip contains no information on the location…

Van der Burg, Erik; Olivers, Christian N. L.; Bronkhorst, Adelbert W.; Theeuwes, Jan

2008-01-01

94

Improvement, learning and retention of skill at visual search  

Microsoft Academic Search

Three experiments examined factors responsible for improvement in visual search. In Experiment I three groups of subjects were each trained for 3000 trials to search for a particular set of target letters among a particular set of background letters. After intervals of 2, 4, or 6 weeks without further practice they were re-tested, either with the same displays or on

Patrick Rabbitt; Geoffry Cumming; Subhash Vyas

1979-01-01

95

Visual search in natural scenes explained by local color properties.  

PubMed

Success in visually searching for a small object or target in a natural scene depends on many factors, including the spatial structure of the scene and the pattern of observers' eye movements. The aim of this study was to determine to what extent local color properties of natural scenes can account for target-detection performance. A computer-controlled high-resolution color monitor was used to present images of natural scenes containing a small, randomly located, shaded gray sphere, which served as the target. Observers' gaze position was simultaneously monitored with an infrared video eye-tracker. About 60% of the adjusted variance in observers' detection performance was accounted for by local color properties, namely, lightness and the red-green and blue-yellow components of chroma. A similar level of variance was accounted for by observers' fixations. These results suggest that local color can be as influential as gaze position in determining observers' search performance in natural scenes. PMID:22330379

Amano, Kinjiro; Foster, David H; Mould, Matthew S; Oakley, John P

2012-02-01

96

A neural network for visual pattern recognition  

SciTech Connect

A modeling approach, which is a synthetic approach using neural network models, continues to gain importance. In the modeling approach, the authors study how to interconnect neurons to synthesize a brain model, which is a network with the same functions and abilities as the brain. The relationship between modeling neutral networks and neurophysiology resembles that between theoretical physics and experimental physics. Modeling takes synthetic approach, while neurophysiology or psychology takes an analytical approach. Modeling neural networks is useful in explaining the brain and also in engineering applications. It brings the results of neurophysiological and psychological research to engineering applications in the most direct way possible. This article discusses a neural network model thus obtained, a model with selective attention in visual pattern recognition.

Fukushima, K.

1988-03-01

97

Curious George: An Integrated Visual Search Platform  

Microsoft Academic Search

This paper describes an integrated robot system, known as Curious George, that has demonstrated state-of-the-art capabilities to recognize objects in the real world. We describe the capabilities of this system, including: the ability to access web-based training data automatically and in near real-time, the ability to model the visual appearance and 3D shape of a wide variety of object categories,

David Meger; Marius Muja; Scott Helmer; Ankur Gupta; Catherine Gamroth; Tomas Hoffman; Matthew Baumann; Tristram Southey; Pooyan Fazli; Walter Wohlkinger; Pooja Viswanathan; James J. Little; David G. Lowe; James Orwell

2010-01-01

98

When are abrupt onsets found efficiently in complex visual search? Evidence from multielement asynchronous dynamic search.  

PubMed

Previous work has found that search principles derived from simple visual search tasks do not necessarily apply to more complex search tasks. Using a Multielement Asynchronous Dynamic (MAD) visual search task, in which high numbers of stimuli could either be moving, stationary, and/or changing in luminance, Kunar and Watson (M. A Kunar & D. G. Watson, 2011, Visual search in a Multi-element Asynchronous Dynamic (MAD) world, Journal of Experimental Psychology: Human Perception and Performance, Vol 37, pp. 1017-1031) found that, unlike previous work, participants missed a higher number of targets with search for moving items worse than for static items and that there was no benefit for finding targets that showed a luminance onset. In the present research, we investigated why luminance onsets do not capture attention and whether luminance onsets can ever capture attention in MAD search. Experiment 1 investigated whether blinking stimuli, which abruptly offset for 100 ms before reonsetting--conditions known to produce attentional capture in simpler visual search tasks--captured attention in MAD search, and Experiments 2-5 investigated whether giving participants advance knowledge and preexposure to the blinking cues produced efficient search for blinking targets. Experiments 6-9 investigated whether unique luminance onsets, unique motion, or unique stationary items captured attention. The results found that luminance onsets captured attention in MAD search only when they were unique, consistent with a top-down unique feature hypothesis. PMID:23875577

Kunar, Melina A; Watson, Derrick G

2014-02-01

99

Spurious Pop-Out in Visual Search.  

National Technical Information Service (NTIS)

The present study demonstrates that an object embedded in an array of identical objects can pop-out. Dependent on the stimuli preceding the search display, local (chromatic) adaptation causes an identical object to pop-out because it appears to have a col...

J. Theeuwes M. P. Lucassen

1992-01-01

100

Video Google: Efficient Visual Search of Videos  

Microsoft Academic Search

We describe an approach to object retrieval which searches for and localizes all the occurrences of an object in a video, given a query image of the object. The object is represented by a set of viewpoint invariant region descriptors so that recognition can proceed successfully despite changes in viewpoint, illumination and partial occlusion. The temporal continuity of the video

Josef Sivic; Andrew Zisserman

2006-01-01

101

Visual pattern discovery in timed event data  

NASA Astrophysics Data System (ADS)

Business processes have tremendously changed the way large companies conduct their business: The integration of information systems into the workflows of their employees ensures a high service level and thus high customer satisfaction. One core aspect of business process engineering are events that steer the workflows and trigger internal processes. Strict requirements on interval-scaled temporal patterns, which are common in time series, are thereby released through the ordinal character of such events. It is this additional degree of freedom that opens unexplored possibilities for visualizing event data. In this paper, we present a flexible and novel system to find significant events, event clusters and event patterns. Each event is represented as a small rectangle, which is colored according to categorical, ordinal or intervalscaled metadata. Depending on the analysis task, different layout functions are used to highlight either the ordinal character of the data or temporal correlations. The system has built-in features for ordering customers or event groups according to the similarity of their event sequences, temporal gap alignment and stacking of co-occurring events. Two characteristically different case studies dealing with business process events and news articles demonstrate the capabilities of our system to explore event data.

Schaefer, Matthias; Wanner, Franz; Mansmann, Florian; Scheible, Christian; Stennett, Verity; Hasselrot, Anders T.; Keim, Daniel A.

2011-01-01

102

Generation Pattern Search for Different Kinds of Economic Load Dispatch  

Microsoft Academic Search

The binary successive approximation (BSA) based evolutionary search strategy has been proposed to solve economic load dispatch (ELD) problem by searching the generation pattern of committed units. Inequality constraints are taken care during search of generation pattern. To meet the demand, a slack generator is introduced to compensate the perturbation of unmet load during the search. Performance of the algorithm

Jarnail S. Dhillon; D. P. Kothari

2007-01-01

103

A Summary Statistic Representation in Peripheral Vision Explains Visual Search  

PubMed Central

Vision is an active process: we repeatedly move our eyes to seek out objects of interest and explore our environment. Visual search experiments capture aspects of this process, by having subjects look for a target within a background of distractors. Search speed often correlates with target-distractor discriminability; search is faster when the target and distractors look quite different. However, there are notable exceptions. A given discriminability can yield efficient searches (where the target seems to “pop-out”) as well as inefficient ones (where additional distractors make search significantly slower and more difficult). Search is often more difficult when finding the target requires distinguishing a particular configuration or conjunction of features. Search asymmetries abound. These puzzling results have fueled three decades of theoretical and experimental studies. We argue that the key issue in search is the processing of image patches in the periphery, where visual representation is characterized by summary statistics computed over a sizable pooling region. By quantifying these statistics, we predict a set of classic search results, as well as peripheral discriminability of crowded patches such as those found in search displays.

Rosenholtz, Ruth; Huang, Jie; Raj, Alvin; Balas, Benjamin J.; Ilie, Livia

2014-01-01

104

Towards Visual-Search Model Observers for Mass Detection in Breast Tomosynthesis  

PubMed Central

We are investigating human-observer models that perform clinically realistic detection and localization tasks as a means of making reliable assessments of digital breast tomosynthesis images. The channelized non-prewhitening (CNPW) observer uses the background known exactly task for localization and detection. Visual-search observer models attempt to replicate the search patterns of trained radiologists. The visual-search observer described in this paper utilizes a two-phase approach, with an initial holistic search followed by directed analysis and decision making. Gradient template matching is used for the holistic search, and the CNPW observer is used for analysis and decision making. Spherical masses were embedded into anthropomorphic breast phantoms, and simulated projections were made using ray-tracing and a serial cascade model. A localization ROC study was performed on these images using the visual-search model observer and the CNPW observer. Observer performance from the two computer observers was compared to human observer performance. The visual-search observer was able to produce area under the LROC curve values similar to those from human observers; however, more research is needed to increase the robustness of the algorithm.

Lau, Beverly A.; Das, Mini; Gifford, Howard C.

2013-01-01

105

Personalized online information search and visualization  

Microsoft Academic Search

BACKGROUND: The rapid growth of online publications such as the Medline and other sources raises the questions how to get the relevant information efficiently. It is important, for a bench scientist, e.g., to monitor related publications constantly. It is also important, for a clinician, e.g., to access the patient records anywhere and anytime. Although time-consuming, this kind of searching procedure

Dongquan Chen; Helmuth F Orthner; Susan M Sell

2005-01-01

106

Design and Implementation of Cancellation Tasks for Visual Search Strategies and Visual Attention in School Children  

ERIC Educational Resources Information Center

We propose a computer-assisted cancellation test system (CACTS) to understand the visual attention performance and visual search strategies in school children. The main aim of this paper is to present our design and development of the CACTS and demonstrate some ways in which computer techniques can allow the educator not only to obtain more…

Wang, Tsui-Ying; Huang, Ho-Chuan; Huang, Hsiu-Shuang

2006-01-01

107

Fear-enhanced visual search persists after amygdala lesions  

PubMed Central

Previous research has indicated that the amygdala is a critical neural substrate of the emotional modulation of attention. However, a recent case-study suggests that the amygdala may not be essential for all types of emotion-attention interactions. In order to test this hypothesis, we assessed the visual-search performance of patients with unilateral amygdala lesions, matched controls, and medication-matched epilepsy patients with intact amygdalae. All participants completed a visual-search task consisting of trials in which (1) an emotional target was embedded amongst neutral distractors, (2) a neutral target was embedded amongst emotional distractors, or (3) a neutral target was embedded amongst neutral distractors. All participant groups, including those with amygdala lesions, detected emotional targets more efficiently than neutral targets. These data indicate that the amygdala is not necessary for emotion-guided visual search and suggest that other mechanisms beyond the amygdala help guide attention toward threatening stimuli.

Piech, Richard M.; McHugo, Maureen; Smith, Stephen D.; Dukic, Mildred S.; Meer, Joost Van Der; Abou-Khalil, Bassel; Zald, David H.

2010-01-01

108

Signal detection evidence for limited capacity in visual search  

PubMed Central

The nature of capacity limits (if any) in visual search has been a topic of controversy for decades. In 30 years of work, researchers have attempted to distinguish between two broad classes of visual search models. Attention-limited models have proposed two stages of perceptual processing: an unlimited-capacity preattentive stage, and a limited-capacity selective attention stage. Conversely, noise-limited models have proposed a single, unlimited-capacity perceptual processing stage, with decision processes influenced only by stochastic noise. Here, we use signal detection methods to test a strong prediction of attention-limited models. In standard attention-limited models, performance of some searches (feature searches) should only be limited by a preattentive stage. Other search tasks (e.g., spatial configuration search for a “2” among “5”s) should be additionally limited by an attentional bottleneck. We equated average accuracies for a feature and a spatial configuration search over set sizes of 1–8 for briefly presented stimuli. The strong prediction of attention-limited models is that, given overall equivalence in performance, accuracy should be better on the spatial configuration search than on the feature search for set size 1, and worse for set size 8. We confirm this crossover interaction and show that it is problematic for at least one class of one-stage decision models.

Fencsik, David E.; Flusberg, Stephen J.; Horowitz, Todd S.; Wolfe, Jeremy M.

2014-01-01

109

Accommodation response during a prolonged visual search task.  

PubMed

The visual accommodative response is measured during dark field viewing and while engaged in a visual search task. A laser optometer is used to compare performance using microfiche and hard-copy displays. Results indicate a marked bias in the direction of the individual's resting accommodative state during all conditions of display viewing. Implications of these results and those from other studies are discussed with respect to future research in display design. PMID:15676427

Kintz, R T; Bowker, D O

1982-03-01

110

Predictive saccade target selection in superior colliculus during visual search.  

PubMed

Searching for a visual object naturally involves sequences of gaze fixations, during which the current foveal image is analyzed and the next object to inspect is selected as a saccade target. Fixation durations during such sequences are short, suggesting that saccades may be concurrently processed. Therefore, the selection of the next saccade target may occur before the current saccade target is acquired. To test this hypothesis, we trained four female rhesus monkeys (Macaca mulatta) to perform a multiple-fixation visual conjunction search task. We simultaneously recorded the activity of sensorimotor neurons in the midbrain superior colliculus (SC) in two monkeys. In this task, monkeys made multiple fixations before foveating the target. Fixation durations were significantly shorter than the latency of the initial responses to the search display, with approximately one-quarter being shorter than the shortest response latencies. The time at which SC sensorimotor activity discriminated the target from distracters occurred significantly earlier for the selection of subsequent fixations than for the selection of the first fixation. Target selection during subsequent fixations occurred even before the visual afferent delay in more than half of the neuronal sample, suggesting that the process of selection can encompass at least two future saccade targets. This predictive selection was present even when differences in saccade latencies were taken into account. Altogether, these findings demonstrate how neural representations on the visual salience map are processed in parallel, thus facilitating visual search. PMID:24741054

Shen, Kelly; Paré, Martin

2014-04-16

111

Visual search for arbitrary objects in real scenes  

Microsoft Academic Search

How efficient is visual search in real scenes? In searches for targets among arrays of randomly placed distractors, efficiency\\u000a is often indexed by the slope of the reaction time (RT) × Set Size function. However, it may be impossible to define set size\\u000a for real scenes. As an approximation, we hand-labeled 100 indoor scenes and used the number of labeled

Jeremy M. Wolfe; George A. Alvarez; Ruth Rosenholtz; Yoana I. Kuzmova; Ashley M. Sherman

2011-01-01

112

Types and frequency of errors in visual search  

Microsoft Academic Search

The experimental method allowed false-positive as well as false-negative errors to be measured during visual search. Data\\u000a were collected from eight Ss on four target-set size conditions on each of 25 days in order to determine whether the finding\\u000a that search rate is independent of target-set size after practice might be attributable to a systematic variation in total\\u000a error rate

Marianne W. Kristofferson

1972-01-01

113

Eye movements in active visual search: a computable phenomenological model.  

PubMed

We present a computational model and corresponding computer simulations that mimic phenomenologically the eye movement trajectories observed in a conjunctive visual search task. The element of randomness is captured in the model through a Monte Carlo selection of a particular eye movement based on its probability, which depends on three factors, adjusted to match to the observed saccade amplitude distribution, forward bias in consecutive saccades, and return rates. Memory is assumed to operate through tagging of objects already recognized as nontargets, which, in turn, requires their processing within the attentional area of conspicuity (AC). That AC is adjusted so that computer simulations optimally reproduce the distribution of the number of saccades, the failure rate for capturing the target, and the return rate to previously inspected locations. For their viability, computer simulations critically depend on memory's being long-ranged. In turn, the simulations confirm the formation of circulating or spiraling patterns in the observed eye trajectories. We also relate consistently the average number of saccades per trial to the saccade amplitude distribution by modeling analytically the combined roles of the AC in attention and memory. The full Supplemental Appendix A for this article may be downloaded from http://app.psychonomic-journals.org/content/supplemental. PMID:20139446

Keech, T D; Resca, L

2010-02-01

114

Segmentation by depth does not always facilitate visual search.  

PubMed

In visual search, target detection times are relatively insensitive to set size when targets and distractors differ on a single feature dimension. Search can be confined to only those elements sharing a single feature, such as color (Egeth, Virzi, & Garbart, 1984). These findings have been taken as evidence that elementary feature dimensions support a parallel segmentation of a scene into discrete sets of items. Here we explored if relative depth (signaled by binocular disparity) could support a similar parallel segmentation by examining the effects of distributing distracting elements across two depth planes. Three important empirical findings emerged. First, when the target was a feature singleton on the target depth plane, but a conjunction search among distractors on the nontarget plane, search efficiency increased compared to a single depth plane. Second, benefits of segmentation in depth were only observed when the target depth plane was known in advance. Third, no benefit of segmentation in depth was observed when both planes required a conjunction search, even with prior knowledge of the target depth plane. Overall, the benefit of distributing the elements of a search set across two depth planes was observed only when the two planes differed both in binocular disparity and in the elementary feature composition of individual elements. We conclude that segmentation of the search array into two depth planes can facilitate visual search, but unlike color or other elementary properties, does not provide an automatic, preattentive segmentation. PMID:23847304

Finlayson, Nonie J; Remington, Roger W; Retell, James D; Grove, Philip M

2013-01-01

115

Visual Exploratory Search of Relationship Graphs on Smartphones  

PubMed Central

This paper presents a novel framework for Visual Exploratory Search of Relationship Graphs on Smartphones (VESRGS) that is composed of three major components: inference and representation of semantic relationship graphs on the Web via meta-search, visual exploratory search of relationship graphs through both querying and browsing strategies, and human-computer interactions via the multi-touch interface and mobile Internet on smartphones. In comparison with traditional lookup search methodologies, the proposed VESRGS system is characterized with the following perceived advantages. 1) It infers rich semantic relationships between the querying keywords and other related concepts from large-scale meta-search results from Google, Yahoo! and Bing search engines, and represents semantic relationships via graphs; 2) the exploratory search approach empowers users to naturally and effectively explore, adventure and discover knowledge in a rich information world of interlinked relationship graphs in a personalized fashion; 3) it effectively takes the advantages of smartphones’ user-friendly interfaces and ubiquitous Internet connection and portability. Our extensive experimental results have demonstrated that the VESRGS framework can significantly improve the users’ capability of seeking the most relevant relationship information to their own specific needs. We envision that the VESRGS framework can be a starting point for future exploration of novel, effective search strategies in the mobile Internet era.

Ouyang, Jianquan; Zheng, Hao; Kong, Fanbin; Liu, Tianming

2013-01-01

116

Neural substrates for visual pattern recognition learning in Igo  

Microsoft Academic Search

Different contexts require different visual pattern recognitions even for identical retinal inputs, and acquiring expertise in various visual-cognitive skills requires long-term training to become capable of recognizing relevant visual patterns in otherwise ambiguous stimuli. This 3-Tesla fMRI experiment exploited shikatsu-mondai (life-or-death problems) in the Oriental board game of Igo (Go) to identify the neural substrates supporting this gradual and adaptive

Kosuke Itoh; Hideaki Kitamura; Yukihiko Fujii; Tsutomu Nakada

2008-01-01

117

Measuring Search Efficiency in Complex Visual Search Tasks: Global and Local Clutter  

ERIC Educational Resources Information Center

Set size and crowding affect search efficiency by limiting attention for recognition and attention against competition; however, these factors can be difficult to quantify in complex search tasks. The current experiments use a quantitative measure of the amount and variability of visual information (i.e., clutter) in highly complex stimuli (i.e.,…

Beck, Melissa R.; Lohrenz, Maura C.; Trafton, J. Gregory

2010-01-01

118

Accurate expectancies diminish perceptual distraction during visual search  

PubMed Central

The load theory of visual attention proposes that efficient selective perceptual processing of task-relevant information during search is determined automatically by the perceptual demands of the display. If the perceptual demands required to process task-relevant information are not enough to consume all available capacity, then the remaining capacity automatically and exhaustively “spills-over” to task-irrelevant information. The spill-over of perceptual processing capacity increases the likelihood that task-irrelevant information will impair performance. In two visual search experiments, we tested the automaticity of the allocation of perceptual processing resources by measuring the extent to which the processing of task-irrelevant distracting stimuli was modulated by both perceptual load and top-down expectations using behavior, functional magnetic resonance imaging, and electrophysiology. Expectations were generated using a trial-by-trial cue that provided information about the likely load of the upcoming visual search task. When the cues were valid, behavioral interference was eliminated and the influence of load on frontoparietal and visual cortical responses was attenuated relative to when the cues were invalid. In conditions in which task-irrelevant information interfered with performance and modulated visual activity, individual differences in mean blood oxygenation level dependent responses measured from the left intraparietal sulcus were negatively correlated with individual differences in the severity of distraction. These results are consistent with the interpretation that a top-down biasing mechanism interacts with perceptual load to support filtering of task-irrelevant information.

Sy, Jocelyn L.; Guerin, Scott A.; Stegman, Anna; Giesbrecht, Barry

2014-01-01

119

Context-aware discovery of visual co-occurrence patterns.  

PubMed

Once an image is decomposed into a number of visual primitives, e.g., local interest points or regions, it is of great interests to discover meaningful visual patterns from them. Conventional clustering of visual primitives, however, usually ignores the spatial and feature structure among them, thus cannot discover high-level visual patterns of complex structure. To overcome this problem, we propose to consider spatial and feature contexts among visual primitives for pattern discovery. By discovering spatial co-occurrence patterns among visual primitives and feature co-occurrence patterns among different types of features, our method can better address the ambiguities of clustering visual primitives. We formulate the pattern discovery problem as a regularized k-means clustering where spatial and feature contexts are served as constraints to improve the pattern discovery results. A novel self-learning procedure is proposed to utilize the discovered spatial or feature patterns to gradually refine the clustering result. Our self-learning procedure is guaranteed to converge and experiments on real images validate the effectiveness of our method. PMID:24808348

Hongxing Wang; Junsong Yuan; Ying Wu

2014-04-01

120

Eye movements during visual search in patients with glaucoma  

PubMed Central

Background Glaucoma has been shown to lead to disability in many daily tasks including visual search. This study aims to determine whether the saccadic eye movements of people with glaucoma differ from those of people with normal vision, and to investigate the association between eye movements and impaired visual search. Methods Forty patients (mean age: 67 [SD: 9] years) with a range of glaucomatous visual field (VF) defects in both eyes (mean best eye mean deviation [MD]: –5.9 (SD: 5.4) dB) and 40 age-related people with normal vision (mean age: 66 [SD: 10] years) were timed as they searched for a series of target objects in computer displayed photographs of real world scenes. Eye movements were simultaneously recorded using an eye tracker. Average number of saccades per second, average saccade amplitude and average search duration across trials were recorded. These response variables were compared with measurements of VF and contrast sensitivity. Results The average rate of saccades made by the patient group was significantly smaller than the number made by controls during the visual search task (P?=?0.02; mean reduction of 5.6% (95% CI: 0.1 to 10.4%). There was no difference in average saccade amplitude between the patients and the controls (P?=?0.09). Average number of saccades was weakly correlated with aspects of visual function, with patients with worse contrast sensitivity (PR logCS; Spearman’s rho: 0.42; P?=?0.006) and more severe VF defects (best eye MD; Spearman’s rho: 0.34; P?=?0.037) tending to make less eye movements during the task. Average detection time in the search task was associated with the average rate of saccades in the patient group (Spearman’s rho?=??0.65; P?visual search by this group of patients was fewer than those made by people with normal vision of a similar average age. There was wide variability in saccade rate in the patients but there was an association between an increase in this measure and better performance in the search task. Assessment of eye movements in individuals with glaucoma might provide insight into the functional deficits of the disease.

2012-01-01

121

Enhancing visual search abilities of people with intellectual disabilities.  

PubMed

This study aimed to evaluate the effects of cueing in visual search paradigm for people with and without intellectual disabilities (ID). A total of 36 subjects (18 persons with ID and 18 persons with normal intelligence) were recruited using convenient sampling method. A series of experiments were conducted to compare guided cue strategies using either motion contrast or additional cue to basic search task. Repeated measure ANOVA and post hoc multiple comparison tests were used to compare each cue strategy. Results showed that the use of guided strategies was able to capture focal attention in an autonomic manner in the ID group (Pillai's Trace=5.99, p<0.0001). Both guided cue and guided motion search tasks demonstrated functionally similar effects that confirmed the non-specific character of salience. These findings suggested that the visual search efficiency of people with ID was greatly improved if the target was made salient using cueing effect when the complexity of the display increased (i.e. set size increased). This study could have an important implication for the design of the visual searching format of any computerized programs developed for people with ID in learning new tasks. PMID:18359188

Li-Tsang, Cecilia W P; Wong, Jackson K K

2009-01-01

122

Irrelevant objects of expertise compete with faces during visual search  

PubMed Central

Prior work suggests that non-face objects of expertise can interfere with the perception of faces when the two categories are alternately presented, suggesting competition for shared perceptual resources. Here we ask whether task-irrelevant distractors from a category of expertise compete when faces are presented in a standard visual search task. Participants searched for a target (face or sofa) in an array containing both relevant and irrelevant distractors. The number of distractors from the target category (face or sofa) remained constant, while the number of distractors from the irrelevant category (cars) varied. Search slopes, calculated as a function of the number of irrelevant cars, were correlated with car expertise. The effect was not due to car distractors grabbing attention because they did not compete with sofa targets. Objects of expertise interfere with face perception even when they are task irrelevant, visually distinct and separated in space from faces.

McGugin, Rankin W.; McKeeff, Thomas J.; Tong, Frank; Gauthier, Isabel

2010-01-01

123

Children's perceptual organisation of hierarchical visual patterns  

Microsoft Academic Search

Children's perceptual organisation of hierarchical patterns was investigated in two experiments through similarity judgements. Previous studies with adults demonstrated that the perceptual relations between the global configuration and the local elements of such patterns depend critically on the number of elements embedded in the pattern: Patterns composed of a few, relatively large elements are perceived in terms of global form

Ruth Kimchi

1990-01-01

124

Defining the notion of visual pattern for predicting visual target distinctness in a complex rural background  

NASA Astrophysics Data System (ADS)

The goal of this paper is to analyze a new notion of visual pattern that captures the primary details for the task of quantifying the visual distinctness of targets in complex natural scenes. We show that given an objective function, which is defined as the mean of the fraction of correctly classified targets across a number of datasets and whose maximization is desired, the optimal notion of visual pattern in a complex natural background can be defined as congruence in a certain statistical structure at attentional points across a range of 2D frequency bands. We draw this conclusion from several experiments in which the best definition of visual pattern is estimated based on the relation between the visual target distinctness measured by human observers and a computational distance that applies a simple decision rule to the differences between segregated visual patterns.

Fdez-Vidal, Xose R.; Garcia, J. A.; Fdez-Valdivia, J.; Rodriguez-Sanchez, Rosa

2000-02-01

125

In search of the emotional face: anger versus happiness superiority in visual search.  

PubMed

Previous research has provided inconsistent results regarding visual search for emotional faces, yielding evidence for either anger superiority (i.e., more efficient search for angry faces) or happiness superiority effects (i.e., more efficient search for happy faces), suggesting that these results do not reflect on emotional expression, but on emotion (un-)related low-level perceptual features. The present study investigated possible factors mediating anger/happiness superiority effects; specifically search strategy (fixed vs. variable target search; Experiment 1), stimulus choice (Nimstim database vs. Ekman & Friesen database; Experiments 1 and 2), and emotional intensity (Experiment 3 and 3a). Angry faces were found faster than happy faces regardless of search strategy using faces from the Nimstim database (Experiment 1). By contrast, a happiness superiority effect was evident in Experiment 2 when using faces from the Ekman and Friesen database. Experiment 3 employed angry, happy, and exuberant expressions (Nimstim database) and yielded anger and happiness superiority effects, respectively, highlighting the importance of the choice of stimulus materials. Ratings of the stimulus materials collected in Experiment 3a indicate that differences in perceived emotional intensity, pleasantness, or arousal do not account for differences in search efficiency. Across three studies, the current investigation indicates that prior reports of anger or happiness superiority effects in visual search are likely to reflect on low-level visual features associated with the stimulus materials used, rather than on emotion. PMID:23527503

Savage, Ruth A; Lipp, Ottmar V; Craig, Belinda M; Becker, Stefanie I; Horstmann, Gernot

2013-08-01

126

The Role of Visual Working Memory in the Control of Gaze during Visual Search  

PubMed Central

The interactions among visual working memory (VWM), attention, and gaze control were investigated in a visual search task that was performed while a color was held in VWM for a concurrent discrimination task. In the search task, participants were required to foveate a cued item within a circular array of colored objects. During the saccade to the target, the array was sometimes rotated so that the eyes landed midway between the target object and an adjacent distractor object, necessitating a second saccade to foveate the target. When the color of the adjacent distractor matched a color being maintained in VWM, execution of this secondary saccade was impaired, indicating that the current contents of VWM bias saccade targeting mechanisms that ordinarily direct gaze toward target objects during visual search.

Hollingworth, Andrew; Luck, Steven J.

2009-01-01

127

Crowded visual search in children with normal vision and children with visual impairment.  

PubMed

This study investigates the influence of oculomotor control, crowding, and attentional factors on visual search in children with normal vision ([NV], n=11), children with visual impairment without nystagmus ([VI-nys], n=11), and children with VI with accompanying nystagmus ([VI+nys], n=26). Exclusion criteria for children with VI were: multiple impairments and visual acuity poorer than 20/400 or better than 20/50. Three search conditions were presented: a row with homogeneous distractors, a matrix with homogeneous distractors, and a matrix with heterogeneous distractors. Element spacing was manipulated in 5 steps from 2 to 32 minutes of arc. Symbols were sized 2 times the threshold acuity to guarantee visibility for the VI groups. During simple row and matrix search with homogeneous distractors children in the VI+nys group were less accurate than children with NV at smaller spacings. Group differences were even more pronounced during matrix search with heterogeneous distractors. Search times were longer in children with VI compared to children with NV. The more extended impairments during serial search reveal greater dependence on oculomotor control during serial compared to parallel search. PMID:24456806

Huurneman, Bianca; Cox, Ralf F A; Vlaskamp, Björn N S; Boonstra, F Nienke

2014-03-01

128

VISUAL SALIENCY DOES NOT ACCOUNT FOR EYE MOVEMENTS DURING VISUAL SEARCH IN REAL-WORLD SCENES  

Microsoft Academic Search

Abstract We tested the hypothesis that fixation locations during scene viewing,are primarily determined,by visual salience. Eye movements,were collected from participants who viewed photographs of real-world scenes during an active search task. Visual salience as determined by a popular computational,model did not predict region-to-region saccades or saccade sequences any better than did a random,model. Consistent with other reports in the literature,

JOHN M. HENDERSON; JAMES R. BROCKMOLE; MONICA S. CASTELHANO; Michael Mack

129

Visualizing Sequential Patterns for Text Mining  

Microsoft Academic Search

A sequential pattern in data mining is a finite series of elements such as A ? B ? C ? D where A, B, C, and D are elements of the same domain. The mining of se- quential patterns is designed to find patterns of dis- crete events that frequently happen in the same ar- rangement along a timeline. Like

Pak Chung Wong; Wendy Cowley; Harlan Foote; Elizabeth Jurrus; Jim Thomas

2000-01-01

130

Macular degeneration affects eye movement behavior during visual search  

PubMed Central

Patients with a scotoma in their central vision (e.g., due to macular degeneration, MD) commonly adopt a strategy to direct the eyes such that the image falls onto a peripheral location on the retina. This location is referred to as the preferred retinal locus (PRL). Although previous research has investigated the characteristics of this PRL, it is unclear whether eye movement metrics are modulated by peripheral viewing with a PRL as measured during a visual search paradigm. To this end, we tested four MD patients in a visual search paradigm and contrasted their performance with a healthy control group and a healthy control group performing the same experiment with a simulated scotoma. The experiment contained two conditions. In the first condition the target was an unfilled circle hidden among c-shaped distractors (serial condition) and in the second condition the target was a filled circle (pop-out condition). Saccadic search latencies for the MD group were significantly longer in both conditions compared to both control groups. Results of a subsequent experiment indicated that this difference between the MD and the control groups could not be explained by a difference in target selection sensitivity. Furthermore, search behavior of MD patients was associated with saccades with smaller amplitudes toward the scotoma, an increased intersaccadic interval and an increased number of eye movements necessary to locate the target. Some of these characteristics, such as the increased intersaccadic interval, were also observed in the simulation group, which indicate that these characteristics are related to the peripheral viewing itself. We suggest that the combination of the central scotoma and peripheral viewing can explain the altered search behavior and no behavioral evidence was found for a possible reorganization of the visual system associated with the use of a PRL. Thus the switch from a fovea-based to a PRL-based reference frame impairs search efficiency.

Van der Stigchel, Stefan; Bethlehem, Richard A. I.; Klein, Barrie P.; Berendschot, Tos T. J. M.; Nijboer, Tanja C. W.; Dumoulin, Serge O.

2013-01-01

131

When do I quit? The search termination problem in visual search.  

PubMed

In visual search tasks, observers look for targets in displays or scenes containing distracting, non-target items. Most of the research on this topic has concerned the finding of those targets. Search termination is a less thoroughly studied topic. When is it time to abandon the current search? The answer is fairly straight forward when the one and only target has been found (There are my keys.). The problem is more vexed if nothing has been found (When is it time to stop looking for a weapon at the airport checkpoint?) or when the number of targets is unknown (Have we found all the tumors?). This chapter reviews the development of ideas about quitting time in visual search and offers an outline of our current theory. PMID:23437634

Wolfe, Jeremy M

2012-01-01

132

VISUALIZATION OF SPATIO-TEMPORAL PATTERNS IN PUBLIC TRANSPORT DATA  

Microsoft Academic Search

In this paper, we discuss geovisualization techniques to explore spatio-temporal patterns formed by people traveling through public transport system (PTS). The Spatio-temporal reasoning by PTS operators\\/policy makers to extract patterns from public transport system data is studied. The resulting questions are related to basic visual tasks like locate, identify, associate and compare. These visual tasks are incorporated in a set

Menno-Jan Kraak

133

Visual acuity and pattern of visual field loss at presentation in pituitary adenoma.  

PubMed

Our purpose was to analyse the demographics, prevalence and pattern of visual field defects in patients with pituitary adenoma. We prospectively recruited 103 consecutive patients (206 eyes) presenting to a neurosurgical unit with pituitary adenoma. Ophthalmological examination and standard automated perimetry (Humphrey, 24-2 threshold) was performed. Severity of visual field defects was also assessed. The mean population age was 53.9 years (standard deviation=15). Visual loss was the most common reason for presentation (39%) followed by endocrine abnormality (21%) and headache (15%). Patients with endocrine abnormality on presentation were 10.9 years younger than those presenting with visual loss (p=0.001). Bitemporal defects were the most prevalent pattern (n=22, 41%) followed by homonymous defects (n=7, 13%). Of the patients with visual field loss, 33% had unilateral visual field defects. The mean visual acuity in those with bitemporal defects was 6/7.5 with half of these patients having 6/6 vision in both eyes. In conclusion, the majority of patients with pituitary adenoma have visual acuity better than 6/7.5 despite having visual field defects. While a bitemporal pattern of visual field loss is the most common, a significant proportion of patients had unilateral and altitudinal defects. Assessment of the visual field is essential to rule out chiasmal compression. PMID:24656736

Ogra, Siddharth; Nichols, Andrew D; Stylli, Stanley; Kaye, Andrew H; Savino, Peter J; Danesh-Meyer, Helen V

2014-05-01

134

Reading and Visual Search: A Developmental Study in Normal Children  

PubMed Central

Studies dealing with developmental aspects of binocular eye movement behaviour during reading are scarce. In this study we have explored binocular strategies during reading and during visual search tasks in a large population of normal young readers. Binocular eye movements were recorded using an infrared video-oculography system in sixty-nine children (aged 6 to 15) and in a group of 10 adults (aged 24 to 39). The main findings are (i) in both tasks the number of progressive saccades (to the right) and regressive saccades (to the left) decreases with age; (ii) the amplitude of progressive saccades increases with age in the reading task only; (iii) in both tasks, the duration of fixations as well as the total duration of the task decreases with age; (iv) in both tasks, the amplitude of disconjugacy recorded during and after the saccades decreases with age; (v) children are significantly more accurate in reading than in visual search after 10 years of age. Data reported here confirms and expands previous studies on children's reading. The new finding is that younger children show poorer coordination than adults, both while reading and while performing a visual search task. Both reading skills and binocular saccades coordination improve with age and children reach a similar level to adults after the age of 10. This finding is most likely related to the fact that learning mechanisms responsible for saccade yoking develop during childhood until adolescence.

Seassau, Magali; Bucci, Maria-Pia

2013-01-01

135

Retinotopically specific reorganization of visual cortex for tactile pattern recognition  

PubMed Central

Although previous studies have shown that Braille reading and other tactile-discrimination tasks activate the visual cortex of blind and sighted people [1–5], it is not known whether this kind of cross-modal reorganization is influenced by retinotopic organization. We have addressed this question by studying S, a visually impaired adult with the rare ability to read print visually and Braille by touch. S had normal visual development until age six years, and thereafter severe acuity reduction due to corneal opacification, but no evidence of visual-field loss. Functional magnetic resonance imaging (fMRI) revealed that, in S’s early visual areas, tactile information processing activated what would be the foveal representation for normally-sighted individuals, and visual information processing activated what would be the peripheral representation. Control experiments showed that this activation pattern was not due to visual imagery. S’s high-level visual areas which correspond to shape- and object-selective areas in normally-sighted individuals were activated by both visual and tactile stimuli. The retinotopically specific reorganization in early visual areas suggests an efficient redistribution of neural resources in the visual cortex.

Cheung, Sing-Hang; Fang, Fang; He, Sheng; Legge, Gordon E.

2009-01-01

136

A mathematical theory of visual hallucination patterns  

Microsoft Academic Search

Neuronal activity in a two-dimensional net is analyzed in the neighborhood of an instability. Bifurcation theory and group theory are used to demonstrate the existence of a variety of doublyperiodic patterns, hexagons, rolls, etc., as solutions to the field equations for the net activity. It is suggested that these simple geometric patterns are the cortical concomitants of the “form constants”

G. B. Ermentrout; J. D. Cowan

1979-01-01

137

Detailed analysis of distraction induced by in-vehicle verbal interactions on visual search performance  

Microsoft Academic Search

We examined the negative effect of in-vehicle verbal interaction on visual search performance. Twenty participants performed a primary visual search task and a secondary verbal interaction task concurrently. We found that visual search performance deteriorated when the secondary task involving memory retrieval and speech production was performed concurrently. Moreover, a detailed analysis of the reaction time as a function of

Kazumitsu Shinohara; Takahiro Nakamura; Seiji Tatsuta; Youichi Iba

2010-01-01

138

Visual cluster analysis and pattern recognition methods  

DOEpatents

A method of clustering using a novel template to define a region of influence. Using neighboring approximation methods, computation times can be significantly reduced. The template and method are applicable and improve pattern recognition techniques.

Osbourn, Gordon Cecil (Albuquerque, NM); Martinez, Rubel Francisco (Albuquerque, NM)

2001-01-01

139

The Visualization of the Citation Patterns of Some Canadian Journals  

Microsoft Academic Search

In order to easily see the citation patterns of a journal or subject area it is very useful to use a graphical diagram to visualize all the connections between journals. Using data from derived from the Journal Citation Reports, this study investigates the citation patterns of three Canadian Journals in three subject areas: library and information science, psychology and mathematics.

Michael J. Nelson

140

Visual Object Pattern Separation Varies in Older Adults  

ERIC Educational Resources Information Center

Young and nondemented older adults completed a visual object continuous recognition memory task in which some stimuli (lures) were similar but not identical to previously presented objects. The lures were hypothesized to result in increased interference and increased pattern separation demand. To examine variability in object pattern separation…

Holden, Heather M.; Toner, Chelsea; Pirogovsky, Eva; Kirwan, C. Brock; Gilbert, Paul E.

2013-01-01

141

Cerebral metabolism and patterned visual stimulation: a positron emission tomographic study of the human visual cortex.  

PubMed

We studied the impact of visual stimulation upon cerebral metabolism in normal young men using FDG-PET. Results obtained from subjects receiving patterned visual stimulation while performing an ocular fixation task were compared with results from ocular fixation alone. Visual stimulation in the macular region of either hemifield produced significant increases in metabolism of the contralateral posterior striate cortex. Visual stimulation induced highly significant asymmetries in metabolism of the prefrontal and inferior parietal cortices. Metabolic activation in extrastriate areas tended to be right-sided. These findings support the classic notion of retinotopic organization within the primary visual sensory cortex. They also indicate that the patterns of cerebral metabolism are not equivalent between the two cerebral hemispheres. This latter finding suggests that in humans the right cerebral hemisphere may be specialized for visual processing. PMID:3257295

Kushner, M J; Rosenquist, A; Alavi, A; Rosen, M; Dann, R; Fazekas, F; Bosley, T; Greenberg, J; Reivich, M

1988-01-01

142

Supporting the Process of Exploring and Interpreting Space-Time Multivariate Patterns: The Visual Inquiry Toolkit  

PubMed Central

While many data sets carry geographic and temporal references, our ability to analyze these datasets lags behind our ability to collect them because of the challenges posed by both data complexity and tool scalability issues. This study develops a visual analytics approach that leverages human expertise with visual, computational, and cartographic methods to support the application of visual analytics to relatively large spatio-temporal, multivariate data sets. We develop and apply a variety of methods for data clustering, pattern searching, information visualization, and synthesis. By combining both human and machine strengths, this approach has a better chance to discover novel, relevant, and potentially useful information that is difficult to detect by any of the methods used in isolation. We demonstrate the effectiveness of the approach by applying the Visual Inquiry Toolkit we developed to analyze a data set containing geographically referenced, time-varying and multivariate data for U.S. technology industries.

Chen, Jin; MacEachren, Alan M.; Guo, Diansheng

2009-01-01

143

Suppression of salient objects prevents distraction in visual search.  

PubMed

To find objects of interest in a cluttered and continually changing visual environment, humans must often ignore salient stimuli that are not currently relevant to the task at hand. Recent neuroimaging results indicate that the ability to prevent salience-driven distraction depends on the current level of attentional control activity in frontal cortex, but the specific mechanism by which this control activity prevents salience-driven distraction is still poorly understood. Here, we asked whether salience-driven distraction is prevented by suppressing salient distractors or by preferentially up-weighting the relevant visual dimension. We found that salient distractors were suppressed even when they resided in the same feature dimension as the target (that is, when dimensional weighting was not a viable selection strategy). Our neurophysiological measure of suppression--the PD component of the event-related potential--was associated with variations in the amount of time it took to perform the search task: distractors triggered the PD on fast-response trials, but on slow-response trials they triggered activity associated with working memory representation instead. These results demonstrate that during search salience-driven distraction is mitigated by a suppressive mechanism that reduces the salience of potentially distracting visual objects. PMID:24741056

Gaspar, John M; McDonald, John J

2014-04-16

144

Sequential pattern data mining and visualization  

DOEpatents

One or more processors (22) are operated to extract a number of different event identifiers therefrom. These processors (22) are further operable to determine a number a display locations each representative of one of the different identifiers and a corresponding time. The display locations are grouped into sets each corresponding to a different one of several event sequences (330a, 330b, 330c. 330d, 330e). An output is generated corresponding to a visualization (320) of the event sequences (330a, 330b, 330c, 330d, 330e).

Wong, Pak Chung (Richland, WA); Jurrus, Elizabeth R. (Kennewick, WA); Cowley, Wendy E. (Benton City, WA); Foote, Harlan P. (Richland, WA); Thomas, James J. (Richland, WA)

2009-05-26

145

Sequential pattern data mining and visualization  

DOEpatents

One or more processors (22) are operated to extract a number of different event identifiers therefrom. These processors (22) are further operable to determine a number a display locations each representative of one of the different identifiers and a corresponding time. The display locations are grouped into sets each corresponding to a different one of several event sequences (330a, 330b, 330c. 330d, 330e). An output is generated corresponding to a visualization (320) of the event sequences (330a, 330b, 330c, 330d, 330e).

Wong, Pak Chung (Richland, WA); Jurrus, Elizabeth R. (Kennewick, WA); Cowley, Wendy E. (Benton City, WA); Foote, Harlan P. (Richland, WA); Thomas, James J. (Richland, WA)

2011-12-06

146

Neural Representations of Contextual Guidance in Visual Search of Real-World Scenes  

PubMed Central

Exploiting scene context and object– object co-occurrence is critical in guiding eye movements and facilitating visual search, yet the mediating neural mechanisms are unknown. We used functional magnetic resonance imaging while observers searched for target objects in scenes and used multivariate pattern analyses (MVPA) to show that the lateral occipital complex (LOC) can predict the coarse spatial location of observers’ expectations about the likely location of 213 different targets absent from the scenes. In addition, we found weaker but significant representations of context location in an area related to the orienting of attention (intraparietal sulcus, IPS) as well as a region related to scene processing (retrosplenial cortex, RSC). Importantly, the degree of agreement among 100 independent raters about the likely location to contain a target object in a scene correlated with LOC’s ability to predict the contextual location while weaker but significant effects were found in IPS, RSC, the human motion area, and early visual areas (V1, V3v). When contextual information was made irrelevant to observers’ behavioral task, the MVPA analysis of LOC and the other areas’ activity ceased to predict the location of context. Thus, our findings suggest that the likely locations of targets in scenes are represented in various visual areas with LOC playing a key role in contextual guidance during visual search of objects in real scenes.

Preston, Tim J.; Guo, Fei; Das, Koel; Giesbrecht, Barry; Eckstein, Miguel P.

2014-01-01

147

Intertrial Temporal Contextual Cuing: Association across Successive Visual Search Trials Guides Spatial Attention  

ERIC Educational Resources Information Center

Contextual cuing refers to the facilitation of performance in visual search due to the repetition of the same displays. Whereas previous studies have focused on contextual cuing within single-search trials, this study tested whether 1 trial facilitates visual search of the next trial. Participants searched for a T among Ls. In the training phase,…

Ono, Fuminori; Jiang, Yuhong; Kawahara, Jun-ichiro

2005-01-01

148

Rapid searches for complex patterns in biological molecules.  

PubMed Central

The intrinsic redundancy of genetic information makes searching for patterns in biological sequences a difficult task. We have designed an interactive self-documenting computer program called QUEST that allows rapid searching of large DNA and protein data banks for highly redundant consensus sequences or character patterns. QUEST uses a concise language for specifying character patterns containing several levels of ambiguity and pattern arrangement. Examples of the use of this program for sequence data are given. Details of the algorithm and pattern optimization are explained.

Abarbanel, R M; Wieneke, P R; Mansfield, E; Jaffe, D A; Brutlag, D L

1984-01-01

149

Impaired top-down control of visual search in schizophrenia  

PubMed Central

This study examined top-down and bottom-up control of attention in a group of 24 patients with schizophrenia and 16 healthy volunteers. Participants completed a visual search task in which they reported whether a target oval contained a gap. The target was accompanied by 5, 11, or 17 distractors. On some trials, the target was identified by a highly salient feature that was shared by only 2 distractors, causing this feature to “pop out” from the display. This feature provided strong bottom-up information that could be used to direct attention to the target. On other trials, half of the distractors contained this distractor, making these distractors no more salient than the other distractors requiring greater use of top-down control to restrict processing to items containing this feature. Patient visual search efficiency closely approximated control performance in the first trial type. In contrast, patients demonstrated significant slowing of search in the second trial type, which required top-down control. These results suggest schizophrenia does not impair the ability to implement the selection of a target when attention can be guided by bottom-up information, but it does impair the ability to use top-down control mechanisms to guide attention. These results extend prior studies that have focussed on aspects of executive control in complex tasks and suggest that a similar underlying deficit may also impact the performance of perceptual systems.

Gold, James M.; Fuller, Rebecca L.; Robinson, Benjamin M.; Braun, Elsie L.; Luck, Steven J.

2007-01-01

150

A Fast String-Searching Algorithm for Multiple Patterns.  

ERIC Educational Resources Information Center

Describes a string-searching algorithm for multiple patterns in a text string; explains the construction of a pattern-matching machine; presents a theoretical analysis and empirical evidence that supports the sublinearity of the algorithm; and compares this algorithm with the Boyer-Moore algorithm for a single pattern. (Contains 10 references.)…

Uratani, Noriyoshi; Takeda, Masayuki

1993-01-01

151

Adaptation improves performance on a visual search task  

PubMed Central

Temporal context, or adaptation, profoundly affects visual perception. Despite the strength and prevalence of adaptation effects, their functional role in visual processing remains unclear. The effects of spatial context and their functional role are better understood: these effects highlight features that differ from their surroundings and determine stimulus salience. Similarities in the perceptual and physiological effects of spatial and temporal context raise the possibility that they serve similar functions. We therefore tested the possibility that adaptation can enhance stimulus salience. We measured the effects of prolonged (40 s) adaptation to a counterphase grating on performance in a search task in which targets were defined by an orientation offset relative to a background of distracters. We found that, for targets with small orientation offsets, adaptation reduced reaction times and decreased the number of saccades made to find targets. Our results provide evidence that adaptation may function to highlight features that differ from the temporal context in which they are embedded.

Wissig, Stephanie C.; Patterson, Carlyn A.; Kohn, Adam

2013-01-01

152

WORDGRAPH: Keyword-in-Context Visualization for NETSPEAK's Wildcard Search.  

PubMed

The WORDGRAPH helps writers in visually choosing phrases while writing a text. It checks for the commonness of phrases and allows for the retrieval of alternatives by means of wildcard queries. To support such queries, we implement a scalable retrieval engine, which returns high-quality results within milliseconds using a probabilistic retrieval strategy. The results are displayed as WORDGRAPH visualization or as a textual list. The graphical interface provides an effective means for interactive exploration of search results using filter techniques, query expansion and navigation. Our observations indicate that, of three investigated retrieval tasks, the textual interface is sufficient for the phrase verification task, wherein both interfaces support context-sensitive word choice, and the WORDGRAPH best supports the exploration of a phrase’s context or the underlying corpus. Our user study confirms these observations and shows that WORDGRAPH is generally the preferred interface over the textual result list for queries containing multiple wildcards. PMID:22450821

Riehmann, Patrick; Gruendl, Henning; Potthast, Martin; Trenkmann, Martin; Stein, Benno; Froehlich, Bernd

2012-03-22

153

Image pattern recognition supporting interactive analysis and graphical visualization  

NASA Technical Reports Server (NTRS)

Image Pattern Recognition attempts to infer properties of the world from image data. Such capabilities are crucial for making measurements from satellite or telescope images related to Earth and space science problems. Such measurements can be the required product itself, or the measurements can be used as input to a computer graphics system for visualization purposes. At present, the field of image pattern recognition lacks a unified scientific structure for developing and evaluating image pattern recognition applications. The overall goal of this project is to begin developing such a structure. This report summarizes results of a 3-year research effort in image pattern recognition addressing the following three principal aims: (1) to create a software foundation for the research and identify image pattern recognition problems in Earth and space science; (2) to develop image measurement operations based on Artificial Visual Systems; and (3) to develop multiscale image descriptions for use in interactive image analysis.

Coggins, James M.

1992-01-01

154

Visualizing Information in the Biological Sciences: Using WebTheme to Visualize Internet Search Results  

SciTech Connect

Information visualization is an effective method for displaying large data sets in a pictorial or graphical format. The visualization aids researchers and analysts in understanding data by evaluating the content and grouping documents together around themes and concepts. With the ever-growing amount of information available on the Internet, additional methods are needed to analyze and interpret data. WebTheme allows users to harvest thousands of web pages and automatically organize and visualize their contents. WebTheme is an interactive web-based product that provides a new way to investigate and understand large volumes of HTML text-based information. It has the ability to harvest data from the World Wide Web using search terms and selected search engines or by following URLs chosen by the user. WebTheme enables users to rapidly identify themes and concepts found among thousands of pages of text harvested and provides a suite of tools to further explore and analyze special areas of interest within a data set. WebTheme was developed at Pacific Northwest National Laboratory (PNNL) for NASA as a method for generating meaningful, thematic, and interactive visualizations. Through a collaboration with the Laboratory's Information Science and Engineering (IS&E) group, information specialists are providing demonstrations of WebTheme and assisting researchers in analyzing their results. This paper will provide a brief overview of the WebTheme product, and the ways in which the Hanford Technical Library's information specialists are assisting researchers in using this product.

Buxton, Karen A.; Lembo, Mary Frances

2003-08-11

155

Pattern Search Algorithms for Mixed Variable General Constrained Optimization Problems.  

National Technical Information Service (NTIS)

A new class of algorithms for solving nonlinearly constrained mixed variable optimization problems is presented The Audet-Dennis Generalized Pattern Search (GPS) algorithm for bound constrained mixed variable optimization problems is extended to problems ...

M. A. Abramson

2002-01-01

156

Revisiting the category effect: The influence of meaning and search strategy on the efficiency of visual search  

Microsoft Academic Search

A series of experiments evaluated whether the category membership of objects influences the efficiency of visual search (the category effect). Participants were trained to associate meaningful verbal labels with simple shapes so that it was possible to vary the categorical relationship between targets and distractors in the search displays while counterbalancing for the visual similarity of the targets and distractors.

Daniel Smilek; Mike J. Dixon; Philip M. Merikle

2006-01-01

157

Revisiting the category effect: The influence of meaning and search strategy on the efficiency of visual search  

Microsoft Academic Search

A series of experiments evaluated whether the category membership of objects influences the efficiency of visual search (the category effect). Participants were trained to associate meaningful verbal labels with simple shapes so that it was possible to vary the categorical relationship between targets and distractors in the search displays while counterbalancing for the visual similarity of the targets and distractors.

Daniel Smilek; Mike J. Dixon; Philip M. Merikle

2005-01-01

158

Neural substrates for visual pattern recognition learning in Igo.  

PubMed

Different contexts require different visual pattern recognitions even for identical retinal inputs, and acquiring expertise in various visual-cognitive skills requires long-term training to become capable of recognizing relevant visual patterns in otherwise ambiguous stimuli. This 3-Tesla fMRI experiment exploited shikatsu-mondai (life-or-death problems) in the Oriental board game of Igo (Go) to identify the neural substrates supporting this gradual and adaptive learning. In shikatsu-mondai, the player adds stones to the board with the objective of making, or preventing the opponent from making nigan (two eyes), or the topology of figure of eight, with these stones. Without learning the game, passive viewing of shikatsu-mondai activated the occipito-temporal cortices, reflecting visual processing without the recognition of nigan. Several days after two-hour training, passive viewing of the same stimuli additionally activated the premotor area, intraparietal sulcus, and a visual area near the junction of the (left) intraparietal and transverse occipital sulci, demonstrating plastic changes in neuronal responsivity to the stimuli that contained indications of nigan. Behavioral tests confirmed that the participants had successfully learned to recognize nigan and solve the problems. In the newly activated regions, the level of neural activity while viewing the problems correlated positively with the level of achievement in learning. These results conformed to the hypothesis that recognition of a newly learned visual pattern is supported by the activities of fronto-parietal and visual cortical neurons that interact via newly formed functional connections among these regions. These connections would provide the medium by which the fronto-parietal system modulates visual cortical activity to attain behaviorally relevant perceptions. PMID:18621033

Itoh, Kosuke; Kitamura, Hideaki; Fujii, Yukihiko; Nakada, Tsutomu

2008-08-28

159

Pattern visual evoked potential luminance and multiple sclerosis.  

PubMed

Pattern visual evoked potentials (PVEPs) were recorded from 111 patients classified as having possible, probable or definite multiple sclerosis. Patients were stimulated with a checkerboard pattern using high and low luminances in order to test the hypothesis that an attenuated pattern luminance increases the detection rate of PVEP abnormalities. With increasing certainty of diagnosis, there was a concomitant increase in the incidence of PVEP abnormalities. However, there was no evidence that stimulating with a lower luminance pattern enhanced the sensitivity of the test. The same findings were also apparent when the patient data was analyzed according to the presence or absence of a history of optic neuritis or other visual symptoms. It is concluded that, within the luminance limits used in this study, the role of varied luminance in detecting demyelinating lesions in the optic nerves using the PVEP is minimal, although there was some limited evidence that a high level of luminance may be more appropriate than a low level. PMID:1395053

Frith, R W; Shaw, N A; Aitcheson, F

1992-10-01

160

Patterns of Search: Analyzing and Modeling Web Query Refinement  

Microsoft Academic Search

We discuss the construction of probabilistic models centering on temporal pat- terns of query refinement. Our analyses are derived from a large corpus of Web search queries extracted from server logs recorded by a popular Internet search service. We frame the modeling task in terms of pursuing an understanding of probabilistic relationships among temporal patterns of activity, informational goals, and

Tessa Lau; Eric Horvitz

1998-01-01

161

Recognizing patterns of visual field loss using unsupervised machine learning  

NASA Astrophysics Data System (ADS)

Glaucoma is a potentially blinding optic neuropathy that results in a decrease in visual sensitivity. Visual field abnormalities (decreased visual sensitivity on psychophysical tests) are the primary means of glaucoma diagnosis. One form of visual field testing is Frequency Doubling Technology (FDT) that tests sensitivity at 52 points within the visual field. Like other psychophysical tests used in clinical practice, FDT results yield specific patterns of defect indicative of the disease. We used Gaussian Mixture Model with Expectation Maximization (GEM), (EM is used to estimate the model parameters) to automatically separate FDT data into clusters of normal and abnormal eyes. Principal component analysis (PCA) was used to decompose each cluster into different axes (patterns). FDT measurements were obtained from 1,190 eyes with normal FDT results and 786 eyes with abnormal (i.e., glaucomatous) FDT results, recruited from a university-based, longitudinal, multi-center, clinical study on glaucoma. The GEM input was the 52-point FDT threshold sensitivities for all eyes. The optimal GEM model separated the FDT fields into 3 clusters. Cluster 1 contained 94% normal fields (94% specificity) and clusters 2 and 3 combined, contained 77% abnormal fields (77% sensitivity). For clusters 1, 2 and 3 the optimal number of PCA-identified axes were 2, 2 and 5, respectively. GEM with PCA successfully separated FDT fields from healthy and glaucoma eyes and identified familiar glaucomatous patterns of loss.

Yousefi, Siamak; Goldbaum, Michael H.; Zangwill, Linda M.; Medeiros, Felipe A.; Bowd, Christopher

2014-03-01

162

Response Selection in Visual Search: The Influence of Response Compatibility of Nontargets  

ERIC Educational Resources Information Center

The authors used visual search tasks in which components of the classic flanker task (B. A. Eriksen & C. W. Eriksen, 1974) were introduced. In several experiments the authors obtained evidence of parallel search for a target among distractor elements. Therefore, 2-stage models of visual search predict no effect of the identity of those…

Starreveld, Peter A.; Theeuwes, Jan; Mortier, Karen

2004-01-01

163

Searching for Signs, Symbols, and Icons: Effects of Time of Day, Visual Complexity, and Grouping  

ERIC Educational Resources Information Center

Searching for icons, symbols, or signs is an integral part of tasks involving computer or radar displays, head-up displays in aircraft, or attending to road traffic signs. Icons therefore need to be designed to optimize search times, taking into account the factors likely to slow down visual search. Three factors likely to adversely affect visual

McDougall, Sine; Tyrer, Victoria; Folkard, Simon

2006-01-01

164

Interactive visualization of design patterns can help in framework understanding  

Microsoft Academic Search

Framework programming is regarded as one the main advantages of object-oriented software engineering, and is expected to increase software reuse. In exploiting frameworks, however, programmers often face difficulties caused by the complexity of the hidden architecture and the multiplicity of the design decisions that are embedded in a framework. Interactive visualization of design patterns occurring in a framework shows how

Danny B. Lange; Yuichi Nakamura

1995-01-01

165

Java, CORBA, and patterns in a distributed scientific visualization system  

NASA Astrophysics Data System (ADS)

Software engineering is currently undergoing a radical paradigm shift away from monolithic stovepipe applications which are strongly tied to a particular platform. Key enabling technologies, such as Java and the Common Object Request Broker Architecture (CORBA) allow construction of newer systems from distributed objects and components, providing services seamlessly integrated across multiple platforms. Another exciting trend in the software engineering discipline is the use of patterns. Simply put, a pattern is rule which relates a recurring problem and a software configuration which resolves that problem together in a given context. The use of design patterns, Java, and CORBA offer distinct advantages to visualization tool developers, particularly in light of the extreme demands visualization tools place on existing computing platforms. Potential benefits include: tools capable of using distributed computing resources and data repositories the ability to add new functionality and GUIs at runtime, and the ability to develop cross-platform tools without rewriting large functional units and user interfaces. In this paper, we describe our use of design patterns for the development of distributed, cross-platform visualization systems. The visualization systems currently under development are built with Java and C++ components connected via CORBA middleware.

Lakey, Christopher; Espy, Samuel L.; Gould, David

1998-05-01

166

A neural population model for visual pattern detection.  

PubMed

Pattern detection is the bedrock of modern vision science. Nearly half a century ago, psychophysicists advocated a quantitative theoretical framework that connected visual pattern detection with its neurophysiological underpinnings. In this theory, neurons in primary visual cortex constitute linear and independent visual channels whose output is linked to choice behavior in detection tasks via simple read-out mechanisms. This model has proven remarkably successful in accounting for threshold vision. It is fundamentally at odds, however, with current knowledge about the neurophysiological underpinnings of pattern vision. In addition, the principles put forward in the model fail to generalize to suprathreshold vision or perceptual tasks other than detection. We propose an alternative theory of detection in which perceptual decisions develop from maximum-likelihood decoding of a neurophysiologically inspired model of population activity in primary visual cortex. We demonstrate that this theory explains a broad range of classic detection results. With a single set of parameters, our model can account for several summation, adaptation, and uncertainty effects, thereby offering a new theoretical interpretation for the vast psychophysical literature on pattern detection. PMID:23915083

Goris, Robbe L T; Putzeys, Tom; Wagemans, Johan; Wichmann, Felix A

2013-07-01

167

Simulating cooperative behavior in human collective search pattern.  

PubMed

In the world, great natural disasters frequently occur. Along with these disasters, large-scale cooperative searches for missing persons are exigent. Because of the lack of experiments to reproduce the disaster rescue processes, our understanding of how to regulate the collective cooperative searches is still elusive. Here we use an improved Lévy walk model to simulate the rescuers' movements in which direction choice is considered. In our study, we systematically analyze the diffusive mechanism of rescuers' movements, and find that the search pattern shows a high degree of spatial order which displays some inherent features. Our results also indicate that cooperative search promotes rescuers' movements to disperse determinately. PMID:22350073

Li, Keping; Gao, Ziyou

2012-08-01

168

Do the Contents of Visual Working Memory Automatically Influence Attentional Selection During Visual Search?  

PubMed Central

In many theories of cognition, researchers propose that working memory and perception operate interactively. For example, in previous studies researchers have suggested that sensory inputs matching the contents of working memory will have an automatic advantage in the competition for processing resources. The authors tested this hypothesis by requiring observers to perform a visual search task while concurrently maintaining object representations in visual working memory. The hypothesis that working memory activation produces a simple but uncontrollable bias signal leads to the prediction that items matching the contents of working memory will automatically capture attention. However, no evidence for automatic attentional capture was obtained; instead, the participants avoided attending to these items. Thus, the contents of working memory can be used in a flexible manner for facilitation or inhibition of processing.

Woodman, Geoffrey F.; Luck, Steven J.

2007-01-01

169

Generalising the Pattern Rule for Visual Growth Patterns: Actions that Support 8 Year Olds' Thinking  

ERIC Educational Resources Information Center

A common approach used for introducing algebra to young adolescents is an exploration of visual growth patterns and expressing these patterns as functions and algebraic expressions. Past research has indicated that many adolescents experience difficulties with this approach. This paper explores teaching actions and thinking that begins to bridge…

Warren, Elizabeth; Cooper, Tom

2008-01-01

170

Retinal waves coordinate patterned activity throughout the developing visual system.  

PubMed

The morphological and functional development of the vertebrate nervous system is initially governed by genetic factors and subsequently refined by neuronal activity. However, fundamental features of the nervous system emerge before sensory experience is possible. Thus, activity-dependent development occurring before the onset of experience must be driven by spontaneous activity, but the origin and nature of activity in vivo remains largely untested. Here we use optical methods to show in live neonatal mice that waves of spontaneous retinal activity are present and propagate throughout the entire visual system before eye opening. This patterned activity encompassed the visual field, relied on cholinergic neurotransmission, preferentially initiated in the binocular retina and exhibited spatiotemporal correlations between the two hemispheres. Retinal waves were the primary source of activity in the midbrain and primary visual cortex, but only modulated ongoing activity in secondary visual areas. Thus, spontaneous retinal activity is transmitted through the entire visual system and carries patterned information capable of guiding the activity-dependent development of complex intra- and inter-hemispheric circuits before the onset of vision. PMID:23060192

Ackman, James B; Burbridge, Timothy J; Crair, Michael C

2012-10-11

171

Visualizing frequent patterns in large multivariate time series  

NASA Astrophysics Data System (ADS)

The detection of previously unknown, frequently occurring patterns in time series, often called motifs, has been recognized as an important task. However, it is difficult to discover and visualize these motifs as their numbers increase, especially in large multivariate time series. To find frequent motifs, we use several temporal data mining and event encoding techniques to cluster and convert a multivariate time series to a sequence of events. Then we quantify the efficiency of the discovered motifs by linking them with a performance metric. To visualize frequent patterns in a large time series with potentially hundreds of nested motifs on a single display, we introduce three novel visual analytics methods: (1) motif layout, using colored rectangles for visualizing the occurrences and hierarchical relationships of motifs in a multivariate time series, (2) motif distortion, for enlarging or shrinking motifs as appropriate for easy analysis and (3) motif merging, to combine a number of identical adjacent motif instances without cluttering the display. Analysts can interactively optimize the degree of distortion and merging to get the best possible view. A specific motif (e.g., the most efficient or least efficient motif) can be quickly detected from a large time series for further investigation. We have applied these methods to two real-world data sets: data center cooling and oil well production. The results provide important new insights into the recurring patterns.

Hao, M.; Marwah, M.; Janetzko, H.; Sharma, R.; Keim, D. A.; Dayal, U.; Patnaik, D.; Ramakrishnan, N.

2011-01-01

172

Aging effect in pattern, motion and cognitive visual evoked potentials.  

PubMed

An electrophysiological study on the effect of aging on the visual pathway and various levels of visual information processing (primary cortex, associate visual motion processing cortex and cognitive cortical areas) was performed. We examined visual evoked potentials (VEPs) to pattern-reversal, motion-onset (translation and radial motion) and visual stimuli with a cognitive task (cognitive VEPs - P300 wave) at luminance of 17 cd/m(2). The most significant age-related change in a group of 150 healthy volunteers (15-85 years of age) was the increase in the P300 wave latency (2 ms per 1 year of age). Delays of the motion-onset VEPs (0.47 ms/year in translation and 0.46 ms/year in radial motion) and the pattern-reversal VEPs (0.26 ms/year) and the reductions of their amplitudes with increasing subject age (primarily in P300) were also found to be significant. The amplitude of the motion-onset VEPs to radial motion remained the most constant parameter with increasing age. Age-related changes were stronger in males. Our results indicate that cognitive VEPs, despite larger variability of their parameters, could be a useful criterion for an objective evaluation of the aging processes within the CNS. Possible differences in aging between the motion-processing system and the form-processing system within the visual pathway might be indicated by the more pronounced delay in the motion-onset VEPs and by their preserved size for radial motion (a biologically significant variant of motion) compared to the changes in pattern-reversal VEPs. PMID:22503557

Kuba, Miroslav; Kremlá?ek, Jan; Langrová, Jana; Kubová, Zuzana; Szanyi, Jana; Vít, František

2012-06-01

173

Efficient visual-search model observers for PET.  

PubMed

Objective: Scanning model observers have been efficiently applied as a research tool to predict human-observer performance in F-18 positron emission tomography (PET). We investigated whether a visual-search (VS) observer could provide more reliable predictions with comparable efficiency. Methods: Simulated two-dimensional images of a digital phantom featuring tumours in the liver, lungs and background soft tissue were prepared in coronal, sagittal and transverse display formats. A localization receiver operating characteristic (LROC) study quantified tumour detectability as a function of organ and format for two human observers, a channelized non-prewhitening (CNPW) scanning observer and two versions of a basic VS observer. The VS observers compared watershed (WS) and gradient-based search processes that identified focal uptake points for subsequent analysis with the CNPW observer. The model observers treated "background-known-exactly" (BKE) and "background-assumed-homogeneous" assumptions, either searching the entire organ of interest (Task A) or a reduced area that helped limit false positives (Task B). Performance was indicated by area under the LROC curve. Concordance in the localizations between observers was also analysed. Results: With the BKE assumption, both VS observers demonstrated consistent Pearson correlation with humans (Task A: 0.92 and Task B: 0.93) compared with the scanning observer (Task A: 0.77 and Task B: 0.92). The WS VS observer read 624 study test images in 2.0?min. The scanning observer required 0.7?min. Conclusion: Computationally efficient VS can enhance the stability of statistical model observers with regard to uncertainties in PET tumour detection tasks. Advances in knowledge: VS models improve concordance with human observers. PMID:24837105

Gifford, H C

2014-07-01

174

Visual recovery patterns in children with Leber's hereditary optic neuropathy.  

PubMed

Three patients with Leber's hereditary optic neuropathy (LHON) showed spontaneous improvement in visual acuities after months of legal blindness. Two male patients with bilateral subacute visual loss were 14 years of age at presentation. The first male patient had a mitochondrial DNA mutation at nucleotide position 11778. The second male patient was found to be negative for the designated primary mutations (11778, 14484, 3460) and two of the secondary mutations (15257, 9804). The third patient was a 20-year-old female who presented with bilateral optic atrophy. She had been diagnosed as LHON and was found positive for the 3460 mutation when she was 15. These patients' pattern of visual recovery by developing small islands of normal vision within a central scotoma is characteristic in such rare cases of LHON. PMID:14750573

Acaro?lu, G; Kansu, T; Do?ulu, C F

2001-01-01

175

Association and dissociation between detection and discrimination of objects of expertise: Evidence from visual search.  

PubMed

Expertise in face recognition is characterized by high proficiency in distinguishing between individual faces. However, faces also enjoy an advantage at the early stage of basic-level detection, as demonstrated by efficient visual search for faces among nonface objects. In the present study, we asked (1) whether the face advantage in detection is a unique signature of face expertise, or whether it generalizes to other objects of expertise, and (2) whether expertise in face detection is intrinsically linked to expertise in face individuation. We compared how groups with varying degrees of object and face expertise (typical adults, developmental prosopagnosics [DP], and car experts) search for objects within and outside their domains of expertise (faces, cars, airplanes, and butterflies) among a variable set of object distractors. Across all three groups, search efficiency (indexed by reaction time slopes) was higher for faces and airplanes than for cars and butterflies. Notably, the search slope for car targets was considerably shallower in the car experts than in nonexperts. Although the mean face slope was slightly steeper among the DPs than in the other two groups, most of the DPs' search slopes were well within the normative range. This pattern of results suggests that expertise in object detection is indeed associated with expertise at the subordinate level, that it is not specific to faces, and that the two types of expertise are distinct facilities. We discuss the potential role of experience in bridging between low-level discriminative features and high-level naturalistic categories. PMID:24338355

Golan, Tal; Bentin, Shlomo; DeGutis, Joseph M; Robertson, Lynn C; Harel, Assaf

2014-02-01

176

Patterns in the sky: Natural visualization of aircraft flow fields  

NASA Technical Reports Server (NTRS)

The objective of the current publication is to present the collection of flight photographs to illustrate the types of flow patterns that were visualized and to present qualitative correlations with computational and wind tunnel results. Initially in section 2, the condensation process is discussed, including a review of relative humidity, vapor pressure, and factors which determine the presence of visible condensate. Next, outputs from computer code calculations are postprocessed by using water-vapor relationships to determine if computed values of relative humidity in the local flow field correlate with the qualitative features of the in-flight condensation patterns. The photographs are then presented in section 3 by flow type and subsequently in section 4 by aircraft type to demonstrate the variety of condensed flow fields that was visualized for a wide range of aircraft and flight maneuvers.

Campbell, James F.; Chambers, Joseph R.

1994-01-01

177

Visualizing blood flow patterns using streamlines, arrows, and particle paths.  

PubMed

A customized computer program (MRIView) is described for visualizing and quantifying complex blood flow patterns in major vessels, using nongated and cardiac-gated three-dimensional (3D) velocity data obtained with MR velocity-encoded phase pulse sequences. Streamlines, arrows, and particle paths (collectively referred to as "paths") can be computed interactively, using both forward and backward time integration of the velocity field. The program provides interactive cross-sectional and 3D perspective visualization of the paths, with quantification and statistical analysis of average speed, through-plane velocity, cross-sectional area, and flow. Normal flow patterns in the carotid artery, basilar artery tip, ascending aorta, coronary arteries, descending aorta, and renal arteries, as well as abnormal flow patterns in basilar tip aneurysms, have been investigated. The program revealed flow patterns in these regions with features that are well known from Doppler ultrasound and other features that have not been reported previously. The association between specific abnormal flow patterns and development of atherosclerosis suggests that particle paths can be used to assess risk of plaque formation and progression, as well as to evaluate flow dynamics and vascular patency before and after vascular interventions. PMID:9702703

Buonocore, M H

1998-08-01

178

Preemption Effects in Visual Search: Evidence for Low-Level Grouping.  

ERIC Educational Resources Information Center

Eight experiments, each with 10 observers in each condition, show that the visual search for Mueller-Lyer stimuli is based on complete configurations rather than component segments with preemption by low-level groups. Results support the view that rapid visual search can only access higher level, more ecologically relevant structures. (SLD)

Rensink, Ronald A.; Enns, James T.

1995-01-01

179

Multiresolution and local search methods for optimizing visual tracking processes on GPU  

Microsoft Academic Search

Some visual applications, such as virtual blackboards or gesture recognition for HCI applications, rely on precise visual tracking algorithms. In order to provide this accuracy, some refinement methods are needed as a complement to a coarser approach. In this case, Local Search (LS) methods are typically used, as their purpose is the exploration of a search space to improve a

Raúl Cabido; Antonio S. Montemayor; Juan José Pantrigo; Bryson R. Payne

2007-01-01

180

How visual edge features influence cuttlefish camouflage patterning.  

PubMed

Rapid adaptive camouflage is the primary defense of soft-bodied cuttlefish. Previous studies have shown that cuttlefish body patterns are strongly influenced by visual edges in the substrate. The aim of the present study was to examine how cuttlefish body patterning is differentially controlled by various aspects of edges, including contrast polarity, contrast strength, and the presence or absence of "line terminators" introduced into a pattern when continuous edges are fragmented. Spatially high- and low-pass filtered white or black disks, as well as isolated, continuous and fragmented edges varying in contrast, were used to assess activation of cuttlefish skin components. Although disks of both contrast polarities evoked relatively weak disruptive body patterns, black disks activated different skin components than white disks, and high-frequency information alone sufficed to drive the responses to white disks whereas high- and low-frequency information were both required to drive responses to black disks. Strikingly, high-contrast edge fragments evoked substantially stronger body pattern responses than low-contrast edge fragments, whereas the body pattern responses evoked by high-contrast continuous edges were no stronger than those produced by low-contrast edges. This suggests that line terminators vs. continuous edges influence expression of disruptive body pattern components via different mechanisms that are controlled by contrast in different ways. PMID:23499977

Chiao, Chuan-Chin; Ulmer, Kimberly M; Siemann, Liese A; Buresch, Kendra C; Chubb, Charles; Hanlon, Roger T

2013-05-01

181

Enabling Visual Search and Discovery with the Virtual ITM Observatory  

NASA Astrophysics Data System (ADS)

The Virtual ITM Observatory (VITMO) is one of the recently selected NASA domain specific virtual observatories designed to facilitate study of the ionosphere, thermosphere, and mesosphere (ITM) regions. VITMO sits above mission datacenters and provide outside users with the ability to find data sets across multiple datacenters and more importantly, find those datasets that overlap in time and/or space allowing coordinated observations of phenomena. VITMO provides many methods by which the user can search for and select data of interest including restricting selections based on geophysical conditions (solar wind speed, Kp, etc). A recent addition to VITMO is the support for "summary images" that many instrument teams use to allow the user to identify data sets of interest. VITMO has expanded this capability by automatically tying together summary images and the data sets they are derived from. This facility allows the user to "thumb through" the summary images, indicating those of interest, automatically selecting all of the appropriate data products for download. This gives the user an ability to select based on "identified features" that the user finds in the visual representations of the data sets.

Morrison, D.; Immer, L.; Daley, R.; Patrone, D.; Potter, M.; Holder, R.; Barnes, R.; Colclough, C.; Nylund, S.; Yee, J.; Talaat, E.; Russell, J.; Heelis, R.; Kozyra, J.; Bilitza, D.; McGuire, R.; Candey, R.; Fox, P.

2008-05-01

182

Visual interactions conform to pattern decorrelation in multiple cortical areas.  

PubMed

Neural responses to visual stimuli are strongest in the classical receptive field, but they are also modulated by stimuli in a much wider region. In the primary visual cortex, physiological data and models suggest that such contextual modulation is mediated by recurrent interactions between cortical areas. Outside the primary visual cortex, imaging data has shown qualitatively similar interactions. However, whether the mechanisms underlying these effects are similar in different areas has remained unclear. Here, we found that the blood oxygenation level dependent (BOLD) signal spreads over considerable cortical distances in the primary visual cortex, further than the classical receptive field. This indicates that the synaptic activity induced by a given stimulus occurs in a surprisingly extensive network. Correspondingly, we found suppressive and facilitative interactions far from the maximum retinotopic response. Next, we characterized the relationship between contextual modulation and correlation between two spatial activation patterns. Regardless of the functional area or retinotopic eccentricity, higher correlation between the center and surround response patterns was associated with stronger suppressive interaction. In individual voxels, suppressive interaction was predominant when the center and surround stimuli produced BOLD signals with the same sign. Facilitative interaction dominated in the voxels with opposite BOLD signal signs. Our data was in unison with recently published cortical decorrelation model, and was validated against alternative models, separately in different eccentricities and functional areas. Our study provides evidence that spatial interactions among neural populations involve decorrelation of macroscopic neural activation patterns, and suggests that the basic design of the cerebral cortex houses a robust decorrelation mechanism for afferent synaptic input. PMID:23874491

Sharifian, Fariba; Nurminen, Lauri; Vanni, Simo

2013-01-01

183

Visualization of search results: a comparative evaluation of text, 2D, and 3D interfaces  

Microsoft Academic Search

Although there have been many prototypes of visualization in support of information retrieval, there has been little systematic evaluation that distinguishes the benefits of the visualization per se from that of various accompanying features. The current study focuses on such an evaluation of NIRVE, a tool that supports visualization of search results. Insofar as possible, functionally equivalent 3D, 2D, and

Marc M. Sebrechts; John V. Cugini; Sharon J. Laskowski; Joanna Vasilakis; Michael S. Miller

1999-01-01

184

Advanced analysis of free visual exploration patterns in schizophrenia  

PubMed Central

Background: Visual scanpath analyses provide important information about attention allocation and attention shifting during visual exploration of social situations. This study investigated whether patients with schizophrenia simply show restricted free visual exploration behavior reflected by reduced saccade frequency and increased fixation duration or whether patients use qualitatively different exploration strategies than healthy controls. Methods: Scanpaths of 32 patients with schizophrenia and age-matched 33 healthy controls were assessed while participants freely explored six photos of daily life situations (20 s/photo) evaluated for cognitive complexity and emotional strain. Using fixation and saccade parameters, we compared temporal changes in exploration behavior, cluster analyses, attentional landscapes, and analyses of scanpath similarities between both groups. Results: We found fewer fixation clusters, longer fixation durations within a cluster, fewer changes between clusters, and a greater increase of fixation duration over time in patients compared to controls. Scanpath patterns and attentional landscapes in patients also differed significantly from those of controls. Generally, cognitive complexity and emotional strain had significant effects on visual exploration behavior. This effect was similar in both groups as were physical properties of fixation locations. Conclusions: Longer attention allocation to a given feature in a scene and less attention shifts in patients suggest a more focal processing mode compared to a more ambient exploration strategy in controls. These visual exploration alterations were present in patients independently of cognitive complexity, emotional strain or physical properties of visual cues implying that they represent a rather general deficit. Despite this impairment, patients were able to adapt their scanning behavior to changes in cognitive complexity and emotional strain similar to controls.

Sprenger, Andreas; Friedrich, Monique; Nagel, Matthias; Schmidt, Christiane S.; Moritz, Steffen; Lencer, Rebekka

2013-01-01

185

Visualizing patterns of craniofacial shape variation in Homo sapiens.  

PubMed Central

The geometric morphometric analysis of shape variation in complex biological structures such as the human skull poses a number of specific challenges: the registration of homologous morphologies, the treatment of bilateral symmetry, the graphical representation of form variability in three dimensions and the interpretation of the results in terms of differential growth processes. To visualize complex patterns of shape change, we propose an alternative to classical Cartesian deformation grids in the style of D'Arcy W. Thompson. Reference to the surface structures of the organism under investigation permits a comprehensive visual grasp of shape change and its tentative interpretation in terms of differential growth. The application of this method to the analysis of human craniofacial shape variation reveals distinct modes of growth and development of the neurocranial and viscerocranial regions of the skull. Our data further indicate that variations in the orientation of the viscerocranium relative to the neurocranium impinge on the shapes of the face and the cranial vault.

Zollikofer, Christoph P E; Ponce De Leon, Marcia S

2002-01-01

186

Overcoming hurdles in translating visual search research between the lab and the field.  

PubMed

Research in visual search can be vital to improving performance in careers such as radiology and airport security screening. In these applied, or "field," searches, accuracy is critical, and misses are potentially fatal; however, despite the importance of performing optimally, radiological and airport security searches are nevertheless flawed. Extensive basic research in visual search has revealed cognitive mechanisms responsible for successful visual search as well as a variety of factors that tend to inhibit or improve performance. Ideally, the knowledge gained from such laboratory-based research could be directly applied to field searches, but several obstacles stand in the way of straightforward translation; the tightly controlled visual searches performed in the lab can be drastically different from field searches. For example, they can differ in terms of the nature of the stimuli, the environment in which the search is taking place, and the experience and characteristics of the searchers themselves. The goal of this chapter is to discuss these differences and how they can present hurdles to translating lab-based research to field-based searches. Specifically, most search tasks in the lab entail searching for only one target per trial, and the targets occur relatively frequently, but field searches may contain an unknown and unlimited number of targets, and the occurrence of targets can be rare. Additionally, participants in lab-based search experiments often perform under neutral conditions and have no formal training or experience in search tasks; conversely, career searchers may be influenced by the motivation to perform well or anxiety about missing a target, and they have undergone formal training and accumulated significant experience searching. This chapter discusses recent work that has investigated the impacts of these differences to determine how each factor can influence search performance. Knowledge gained from the scientific exploration of search can be applied to field searches but only when considering and controlling for the differences between lab and field. PMID:23437633

Clark, Kait; Cain, Matthew S; Adamo, Stephen H; Mitroff, Stephen R

2012-01-01

187

Overlapping multivoxel patterns for two levels of visual expectation  

PubMed Central

According to predictive accounts of perception, visual cortical regions encode sensory expectations about the external world, and the violation of those expectations by inputs (surprise). Here, using multi-voxel pattern analysis (MVPA) of functional magnetic resonance imaging (fMRI) data, we asked whether expectations and surprise activate the same pattern of voxels, in face-sensitive regions of the extra-striate visual cortex (the fusiform face area or FFA). Participants viewed pairs of repeating or alternating faces, with high or low probability of repetitions. As in previous studies, we found that repetition suppression (the attenuated BOLD response to repeated stimuli) in the FFA was more pronounced for probable repetitions, consistent with it reflecting reduced surprise to anticipated inputs. Secondly, we observed that repetition suppression and repetition enhancement responses were both consistent across scanner runs, suggesting that both have functional significance, with repetition enhancement possibly indicating the build up of sensory expectation. Critically, we also report that multi-voxels patterns associated with probability and repetition effects were significantly correlated within the left FFA. We argue that repetition enhancement responses and repetition probability effects can be seen as two types of expectation signals, occurring simultaneously, although at different processing levels (lower vs. higher), and different time scales (immediate vs. long term).

de Gardelle, Vincent; Stokes, Mark; Johnen, Vanessa M.; Wyart, Valentin; Summerfield, Christopher

2013-01-01

188

Adaptive two-scale edge detection for visual pattern processing  

NASA Astrophysics Data System (ADS)

Adaptive methods are defined and experimentally studied for a two-scale edge detection process that mimics human visual perception of edges and is inspired by the parvocellular (P) and magnocellular (M) physiological subsystems of natural vision. This two-channel processing consists of a high spatial acuity/coarse contrast channel (P) and a coarse acuity/fine contrast (M) channel. We perform edge detection after a very strong nonlinear image enhancement that uses smart Retinex image processing. Two conditions that arise from this enhancement demand adaptiveness in edge detection. These conditions are the presence of random noise further exacerbated by the enhancement process and the equally random occurrence of dense textural visual information. We examine how to best deal with both phenomena with an automatic adaptive computation that treats both high noise and dense textures as too much information and gracefully shifts from small-scale to medium-scale edge pattern priorities. This shift is accomplished by using different edge-enhancement schemes that correspond with the P- and M-channels of the human visual system. We also examine the case of adapting to a third image condition-namely, too little visual information-and automatically adjust edge-detection sensitivities when sparse feature information is encountered. When this methodology is applied to a sequence of images of the same scene but with varying exposures and lighting conditions, this edge-detection process produces pattern constancy that is very useful for several imaging applications that rely on image classification in variable imaging conditions.

Rahman, Zia-Ur; Jobson, Daniel J.; Woodell, Glenn A.

2009-09-01

189

The Lévy flight paradigm: random search patterns and mechanisms.  

PubMed

Over recent years there has been an accumulation of evidence from a variety of experimental, theoretical, and field studies that many organisms use a movement strategy approximated by Lévy flights when they are searching for resources. Lévy flights are random movements that can maximize the efficiency of resource searches in uncertain environments. This is a highly significant finding because it suggests that Lévy flights provide a rigorous mathematical basis for separating out evolved, innate behaviors from environmental influences. We discuss recent developments in random-search theory, as well as the many different experimental and data collection initiatives that have investigated search strategies. Methods for trajectory construction and robust data analysis procedures are presented. The key to prediction and understanding does, however, lie in the elucidation of mechanisms underlying the observed patterns. We discuss candidate neurological, olfactory, and learning mechanisms for the emergence of Lévy flight patterns in some organisms, and note that convergence of behaviors along such different evolutionary pathways is not surprising given the energetic efficiencies that Lévy flight movement patterns confer. PMID:19449680

Reynolds, A M; Rhodes, C J

2009-04-01

190

High or Low Target Prevalence Increases the Dual-Target Cost in Visual Search  

ERIC Educational Resources Information Center

Previous studies have demonstrated a dual-target cost in visual search. In the current study, the relationship between search for one and search for two targets was investigated to examine the effects of target prevalence and practice. Color-shape conjunction stimuli were used with response time, accuracy and signal detection measures. Performance…

Menneer, Tamaryn; Donnelly, Nick; Godwin, Hayward J.; Cave, Kyle R.

2010-01-01

191

Limitations on the Parallel Guidance of Visual Search: Color × Color and Orientation × Orientation Conjuctions  

Microsoft Academic Search

In visual search for a conjunction it is much more difficult to search for the conjunction of 2 colors or 2 orientations than for Color × Orientation or Color × Shape conjunctions. The result is not limited to particular colors or shapes. Two colors cannot occupy the same spatial location in Color × Color searches. However, Experiments 6 and 7

Jeremy M. Wolfe; Karen P. Yu; Marian I. Stewart; Amy D. Shorter; Stacia R. Friedman-Hill; Kyle R. Cave

1990-01-01

192

Flow pattern visualization in a mimic anaerobic digester using CFD.  

PubMed

Three-dimensional steady-state computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The gas phase was simulated with air and the liquid phase with water. The CFD results were first evaluated using experimental data obtained by computer automated radioactive particle tracking (CARPT). The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However, increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat-bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have an appreciable effect on the flow pattern of the digesters at the range of gas flow rates used. PMID:15685599

Vesvikar, Mehul S; Al-Dahhan, Muthanna

2005-03-20

193

Prediction of shot success for basketball free throws: Visual search strategy.  

PubMed

Abstract In ball games, players have to pay close attention to visual information in order to predict the movements of both the opponents and the ball. Previous studies have indicated that players primarily utilise cues concerning the ball and opponents' body motion. The information acquired must be effective for observing players to select the subsequent action. The present study evaluated the effects of changes in the video replay speed on the spatial visual search strategy and ability to predict free throw success. We compared eye movements made while observing a basketball free throw by novices and experienced basketball players. Correct response rates were close to chance (50%) at all video speeds for the novices. The correct response rate of experienced players was significantly above chance (and significantly above that of the novices) at the normal speed, but was not different from chance at both slow and fast speeds. Experienced players gazed more on the lower part of the player's body when viewing a normal speed video than the novices. The players likely detected critical visual information to predict shot success by properly moving their gaze according to the shooter's movements. This pattern did not change when the video speed was decreased, but changed when it was increased. These findings suggest that temporal information is important for predicting action outcomes and that such outcomes are sensitive to video speed. PMID:24319995

Uchida, Yusuke; Mizuguchi, Nobuaki; Honda, Masaaki; Kanosue, Kazuyuki

2014-08-01

194

Visualizing Neuronal Network Connectivity with Connectivity Pattern Tables  

PubMed Central

Complex ideas are best conveyed through well-designed illustrations. Up to now, computational neuroscientists have mostly relied on box-and-arrow diagrams of even complex neuronal networks, often using ad hoc notations with conflicting use of symbols from paper to paper. This significantly impedes the communication of ideas in neuronal network modeling. We present here Connectivity Pattern Tables (CPTs) as a clutter-free visualization of connectivity in large neuronal networks containing two-dimensional populations of neurons. CPTs can be generated automatically from the same script code used to create the actual network in the NEST simulator. Through aggregation, CPTs can be viewed at different levels, providing either full detail or summary information. We also provide the open source ConnPlotter tool as a means to create connectivity pattern tables.

Nordlie, Eilen; Plesser, Hans Ekkehard

2009-01-01

195

In situ visualization of telomere elongation patterns in human cells  

PubMed Central

The telomerase enzyme plays a critical role in human aging and cancer biology by maintaining telomere length and extending the proliferative lifespan of most stem cells and cancer cells. Despite the importance of this enzyme, our understanding of the mechanisms that regulate its activity and establish telomere length homeostasis in mammalian cells is incomplete, in part because the perfect repetitive nature of telomeric sequence hampers in situ detection of telomere elongation patterns. Here, we describe a novel assay using a mutant telomerase that adds a well-tolerated variant telomeric repeat sequence to telomere ends. By specifically detecting the addition of these variant repeats, we can directly visualize telomere elongation events in human cells. We validate this approach by in situ mapping of telomere elongation patterns within individual nuclei and across a population of cells.

Diolaiti, Morgan E.; Cimini, Beth A.; Kageyama, Robin; Charles, Florie A.; Stohr, Bradley A.

2013-01-01

196

Human cortical mechanisms of visual attention during orienting and search.  

PubMed Central

Functional anatomical studies indicate that a set of neural signals in parietal and frontal cortex mediates the covert allocation of attention to visual locations across a wide variety of visual tasks. This frontoparietal network includes areas, such as the frontal eye field and supplementary eye field. This anatomical overlap suggests that shifts of attention to visual locations of objects recruit areas involved in oculomotor programming and execution. Finally, the fronto-parietal network may be the source of spatial attentional modulations in the ventral visual system during object recognition or discrimination.

Corbetta, M; Shulman, G L

1998-01-01

197

Evolutionary pattern search algorithms for unconstrained and linearly constrained optimization  

SciTech Connect

The authors describe a convergence theory for evolutionary pattern search algorithms (EPSAs) on a broad class of unconstrained and linearly constrained problems. EPSAs adaptively modify the step size of the mutation operator in response to the success of previous optimization steps. The design of EPSAs is inspired by recent analyses of pattern search methods. The analysis significantly extends the previous convergence theory for EPSAs. The analysis applies to a broader class of EPSAs,and it applies to problems that are nonsmooth, have unbounded objective functions, and which are linearly constrained. Further, they describe a modest change to the algorithmic framework of EPSAs for which a non-probabilistic convergence theory applies. These analyses are also noteworthy because they are considerably simpler than previous analyses of EPSAs.

HART,WILLIAM E.

2000-06-01

198

Behavioural coping patterns in Parkinson's patients with visual hallucinations.  

PubMed

Visual Hallucinations are considered to affect about 20%-40% of patients with Parkinson's disease. They are generally seen as a side effect of this long-term illness and can severely affect the daily quality of life of patients. The aim of this study was to determine the coping patterns or strategies used by patients and establish whether the phenomenology and behaviours used by patients enabled control of the phenomenon. Demographic and clinical variables were recorded, including motor measures, cognitive status, and depressive symptoms. Patient with hallucinations were at a more advance stage of the disease and displayed more depressive symptoms than their non-hallucinating counterparts. Most patients used more than one constructive coping strategy, the most common were simple behavioural strategies based around motor action or cognitive approaches resulting in visual modification. In addition, humour was a common technique used by the patients to deal with the phenomenon. Emotional responses varied between patients, but it was found that the actual content of the hallucination was not directly associated with whether it caused trouble to the patient, but perceived stress was strongly correlated with the subjective disturbing nature of visual hallucinations (VHs). This study gives insight into the role of cognitive-behavioural approaches when dealing with VHs and opens up avenues for future studies in helping patient to deal with hallucinations. PMID:23895737

Barnes, Jim; Connelly, Vince; Boubert, Laura; Maravic, Ksenija

2013-09-01

199

Effect of pupil size on multifocal pattern visual evoked potentials.  

PubMed

The purpose of this study was to investigate the influence of pupil diameter on the amplitude and latency of multifocal visual evoked potentials (mfVEP). The multifocal objective perimeter (Accumap; Objectivision) was used to stimulate the visual field at 56 sites extending to 32 degrees using a pseudo-random pattern stimulus. The mfVEP were recorded using bipolar occipital electrodes, 7 min/eye. Ten normal subjects were recruited from the community and one eye was randomly selected for testing. The mfVEP were recorded at four different pupil diameters (2 mm, 4 mm, 6 mm, 8 mm), obtained by applying tropicamide (0.5%) or pilocarpine (2%) in different dilutions. Appropriate refractive correction was provided to overcome cycloplegia and achieve a visual acuity of 6/7.5 or better. Analysis revealed that at most pupil diameters the normalized full field amplitude did not show significant variation, except at the most miotic pupil diameter (2 mm), where the amplitude became reduced, based on 2-way anova and Tukey's T method. There was, however, significant correlation between latency and pupil area (correlation coefficient: upper field -0.63, lower field -0.76). The results suggest that even in the presence of mydriatics or miotics, the mfVEP test can be used to assess diseases that affect amplitude, provided near correction is used. The interpretation of latency, however, must be made with caution, as a borderline conduction defect with a dilated pupil may appear normal. PMID:12880463

Martins, Alessandra; Balachandran, Chandra; Klistorner, Alexander I; Graham, Stuart L; Billson, Francis A

2003-08-01

200

Using visual analytics model for pattern matching in surveillance data  

NASA Astrophysics Data System (ADS)

In a persistent surveillance system huge amount of data is collected continuously and significant details are labeled for future references. In this paper a method to summarize video data as a result of identifying events based on these tagged information is explained, leading to concise description of behavior within a section of extended recordings. An efficient retrieval of various events thus becomes the foundation for determining a pattern in surveillance system observations, both in its extended and fragmented versions. The patterns consisting of spatiotemporal semantic contents are extracted and classified by application of video data mining on generated ontology, and can be matched based on analysts interest and rules set forth for decision making. The proposed extraction and classification method used in this paper uses query by example for retrieving similar events containing relevant features, and is carried out by data aggregation. Since structured data forms majority of surveillance information this Visual Analytics model employs KD-Tree approach to group patterns in variant space and time, thus making it convenient to identify and match any abnormal burst of pattern detected in a surveillance video. Several experimental video were presented to viewers to analyze independently and were compared with the results obtained in this paper to demonstrate the efficiency and effectiveness of the proposed technique.

Habibi, Mohammad S.

2013-03-01

201

Visual search in noise: Revealing the influence of structural cues by gaze-contingent classification image analysis  

Microsoft Academic Search

Visual search experiments have usually involved the detection of a salient target in the presence of distracters against a blank background. In such high signal-to-noise scenarios, observers have been shown to use visual cues such as color, size, and shape of the target to program their saccades during visual search. The degree to which these features affect search performance is

Alan C. Bovik; Lawrence K. Cormack

202

Investigating the role of visual and auditory search in reading and developmental dyslexia  

PubMed Central

It has been suggested that auditory and visual sequential processing deficits contribute to phonological disorders in developmental dyslexia. As an alternative explanation to a phonological deficit as the proximal cause for reading disorders, the visual attention span hypothesis (VA Span) suggests that difficulties in processing visual elements simultaneously lead to dyslexia, regardless of the presence of a phonological disorder. In this study, we assessed whether deficits in processing simultaneously displayed visual or auditory elements is linked to dyslexia associated with a VA Span impairment. Sixteen children with developmental dyslexia and 16 age-matched skilled readers were assessed on visual and auditory search tasks. Participants were asked to detect a target presented simultaneously with 3, 9, or 15 distracters. In the visual modality, target detection was slower in the dyslexic children than in the control group on a “serial” search condition only: the intercepts (but not the slopes) of the search functions were higher in the dyslexic group than in the control group. In the auditory modality, although no group difference was observed, search performance was influenced by the number of distracters in the control group only. Within the dyslexic group, not only poor visual search (high reaction times and intercepts) but also low auditory search performance (d?) strongly correlated with poor irregular word reading accuracy. Moreover, both visual and auditory search performance was associated with the VA Span abilities of dyslexic participants but not with their phonological skills. The present data suggests that some visual mechanisms engaged in “serial” search contribute to reading and orthographic knowledge via VA Span skills regardless of phonological skills. The present results further open the question of the role of auditory simultaneous processing in reading as well as its link with VA Span skills.

Lallier, Marie; Donnadieu, Sophie; Valdois, Sylviane

2013-01-01

203

Visual search for features and conjunctions following declines in the useful field of view  

PubMed Central

Background/Study Context Typical measures for assessing the useful field (UFOV) of view involve many components of attention. The objective of the current experiment was to examine differences in visual search efficiency for older individuals with and without UFOV impairment. Methods The authors used a computerized screening instrument to assess the useful field of view and to characterize participants as having an impaired or normal UFOV. Participants also performed two visual search tasks, a feature search (e.g., search for a green target among red distractors) or a conjunction search (e.g., a green target with a gap on its left or right side among red distractors with gaps on the left or right and green distractors with gaps on the top or bottom). Results Visual search performance did not differ between UFOV impaired and unimpaired individuals when searching for a basic feature. However, search efficiency was lower for impaired individuals than unimpaired individuals when searching for a conjunction of features. Conclusion The results suggest that UFOV decline in normal aging is associated with conjunction search. This finding suggests that the underlying cause of UFOV decline may arise from an overall decline in attentional efficiency. Because the useful field of view is a reliable predictor of driving safety, the results suggest that decline in the everyday visual behavior of older adults might arise from attentional declines.

Cosman, Joshua D.; Lees, Monica N.; Lee, John D.; Rizzo, Matthew; Vecera, Shaun P.

2013-01-01

204

From Salience to Saccades: Multiple-Alternative Gated Stochastic Accumulator Model of Visual Search  

PubMed Central

We describe a stochastic accumulator model demonstrating that visual search performance can be understood as a gated feedforward cascade from a salience map to multiple competing accumulators. The model quantitatively accounts for behavior and predicts neural dynamics of macaque monkeys performing visual search for a target stimulus among different numbers of distractors. The salience accumulated in the model is equated with the spike trains recorded from visually responsive neurons in the frontal eye field. Accumulated variability in the firing rates of these neurons explains choice probabilities and the distributions of correct and error response times with search arrays of different set sizes if the accumulators are mutually inhibitory. The dynamics of the stochastic accumulators quantitatively predict the activity of presaccadic movement neurons that initiate eye movements if gating inhibition prevents accumulation before the representation of stimulus salience emerges. Adjustments in the level of gating inhibition can control trade-offs in speed and accuracy that optimize visual search performance.

Purcell, Braden A.; Schall, Jeffrey D.; Logan, Gordon D.; Palmeri, Thomas J.

2012-01-01

205

Visual search in scenes involves selective and non-selective pathways  

PubMed Central

How do we find objects in scenes? For decades, visual search models have been built on experiments in which observers search for targets, presented among distractor items, isolated and randomly arranged on blank backgrounds. Are these models relevant to search in continuous scenes? This paper argues that the mechanisms that govern artificial, laboratory search tasks do play a role in visual search in scenes. However, scene-based information is used to guide search in ways that had no place in earlier models. Search in scenes may be best explained by a dual-path model: A “selective” path in which candidate objects must be individually selected for recognition and a “non-selective” path in which information can be extracted from global / statistical information.

Wolfe, Jeremy M; Vo, Melissa L-H; Evans, Karla K; Greene, Michelle R

2010-01-01

206

Cognitive issues in searching images with visual queries  

NASA Astrophysics Data System (ADS)

In this paper, we propose our image indexing technique and visual query processing technique. Our mental images are different from the actual retinal images and many things, such as personal interests, personal experiences, perceptual context, the characteristics of spatial objects, and so on, affect our spatial perception. These private differences are propagated into our mental images and so our visual queries become different from the real images that we want to find. This is a hard problem and few people have tried to work on it. In this paper, we survey the human mental imagery system, the human spatial perception, and discuss several kinds of visual queries. Also, we propose our own approach to visual query interpretation and processing.

Yu, ByungGu; Evens, Martha W.

1999-01-01

207

The effects of task difficulty on visual search strategy in virtual 3D displays  

PubMed Central

Analyzing the factors that determine our choice of visual search strategy may shed light on visual behavior in everyday situations. Previous results suggest that increasing task difficulty leads to more systematic search paths. Here we analyze observers' eye movements in an “easy” conjunction search task and a “difficult” shape search task to study visual search strategies in stereoscopic search displays with virtual depth induced by binocular disparity. Standard eye-movement variables, such as fixation duration and initial saccade latency, as well as new measures proposed here, such as saccadic step size, relative saccadic selectivity, and x?y target distance, revealed systematic effects on search dynamics in the horizontal-vertical plane throughout the search process. We found that in the “easy” task, observers start with the processing of display items in the display center immediately after stimulus onset and subsequently move their gaze outwards, guided by extrafoveally perceived stimulus color. In contrast, the “difficult” task induced an initial gaze shift to the upper-left display corner, followed by a systematic left-right and top-down search process. The only consistent depth effect was a trend of initial saccades in the easy task with smallest displays to the items closest to the observer. The results demonstrate the utility of eye-movement analysis for understanding search strategies and provide a first step toward studying search strategies in actual 3D scenarios.

Pomplun, Marc; Garaas, Tyler W.; Carrasco, Marisa

2013-01-01

208

Different predictors of multiple-target search accuracy between nonprofessional and professional visual searchers.  

PubMed

Visual search, locating target items among distractors, underlies daily activities ranging from critical tasks (e.g., looking for dangerous objects during security screening) to commonplace ones (e.g., finding your friends in a crowded bar). Both professional and nonprofessional individuals conduct visual searches, and the present investigation is aimed at understanding how they perform similarly and differently. We administered a multiple-target visual search task to both professional (airport security officers) and nonprofessional participants (members of the Duke University community) to determine how search abilities differ between these populations and what factors might predict accuracy. There were minimal overall accuracy differences, although the professionals were generally slower to respond. However, the factors that predicted accuracy varied drastically between groups; variability in search consistency-how similarly an individual searched from trial to trial in terms of speed-best explained accuracy for professional searchers (more consistent professionals were more accurate), whereas search speed-how long an individual took to complete a search when no targets were present-best explained accuracy for nonprofessional searchers (slower nonprofessionals were more accurate). These findings suggest that professional searchers may utilize different search strategies from those of nonprofessionals, and that search consistency, in particular, may provide a valuable tool for enhancing professional search accuracy. PMID:24266390

Biggs, Adam T; Mitroff, Stephen R

2014-07-01

209

A Study of Temporal Aspect of Posterior Parietal Cortex in Visual Search Using Transcranial Magnetic Stimulation  

NASA Astrophysics Data System (ADS)

It is known that the posterior parietal cortex (PPC) plays a dominant role in spatial processing during visual search. However, the temporal aspect of the PPC is unclear. In the present study, to investigate the temporal aspects of the PPC in feature search, we applied Transcranial Magnetic Stimulation (TMS) over the right PPC with the TMS stimulus onset asynchronies (SOAs) set at 100, 150, 200 and 250 ms after visual search stimulation. We found that when SOA was set at 150 ms, compared to the sham TMS condition, there was a significant elevation in response time when TMS pulses were applied. However, there was no significant difference between the TMS and sham TMS conditions for the other SOA settings. Therefore, we suggest that the spatial processing of feature search is probably processed in the posterior parietal cortex at about 150-170 ms after visual search stimuli presentation.

Ge, Sheng; Matsuoka, Akira; Ueno, Shoogo; Iramina, Keiji

210

Effect of template complexity on visual search and dual-task performance.  

PubMed

Even dissimilar tasks interfere with one another when done together. We used visual search to examine the underlying cause of such interference. In many models, visual search is a process of biased competition controlled by a template describing the target to be sought. When the display is processed, matching against this template guides attention to the target. We show that increasing template complexity increased interference with a dissimilar concurrent task, story memory. This result was independent of reaction time: Increases in template complexity were associated with no increase in search time in Experiment 1 and with a decrease in search time in Experiment 2. The results show that the dual-task demands of visual search reflect the complexity of the template used in task control, and that this factor can be isolated from other sources of difficulty. PMID:15733201

Bourke, Patrick A; Duncan, John

2005-03-01

211

Dynamic modulation of local population activity by rhythm phase in human occipital cortex during a visual search task.  

PubMed

Brain rhythms are more than just passive phenomena in visual cortex. For the first time, we show that the physiology underlying brain rhythms actively suppresses and releases cortical areas on a second-to-second basis during visual processing. Furthermore, their influence is specific at the scale of individual gyri. We quantified the interaction between broadband spectral change and brain rhythms on a second-to-second basis in electrocorticographic (ECoG) measurement of brain surface potentials in five human subjects during a visual search task. Comparison of visual search epochs with a blank screen baseline revealed changes in the raw potential, the amplitude of rhythmic activity, and in the decoupled broadband spectral amplitude. We present new methods to characterize the intensity and preferred phase of coupling between broadband power and band-limited rhythms, and to estimate the magnitude of rhythm-to-broadband modulation on a trial-by-trial basis. These tools revealed numerous coupling motifs between the phase of low-frequency (?, ?, ?, ?, and ? band) rhythms and the amplitude of broadband spectral change. In the ? and ? ranges, the coupling of phase to broadband change is dynamic during visual processing, decreasing in some occipital areas and increasing in others, in a gyrally specific pattern. Finally, we demonstrate that the rhythms interact with one another across frequency ranges, and across cortical sites. PMID:21119778

Miller, Kai J; Hermes, Dora; Honey, Christopher J; Sharma, Mohit; Rao, Rajesh P N; den Nijs, Marcel; Fetz, Eberhard E; Sejnowski, Terrence J; Hebb, Adam O; Ojemann, Jeffrey G; Makeig, Scott; Leuthardt, Eric C

2010-01-01

212

Plans, Patterns, and Move Categories Guiding a Highly Selective Search  

NASA Astrophysics Data System (ADS)

In this paper we present our ideas for an Arimaa-playing program (also called a bot) that uses plans and pattern matching to guide a highly selective search. We restrict move generation to moves in certain move categories to reduce the number of moves considered by the bot significantly. Arimaa is a modern board game that can be played with a standard Chess set. However, the rules of the game are not at all like those of Chess. Furthermore, Arimaa was designed to be as simple and intuitive as possible for humans, yet challenging for computers. While all established Arimaa bots use alpha-beta search with a variety of pruning techniques and other heuristics ending in an extensive positional leaf node evaluation, our new bot, Rat, starts with a positional evaluation of the current position. Based on features found in the current position - supported by pattern matching using a directed position graph - our bot Rat decides which of a given set of plans to follow. The plan then dictates what types of moves can be chosen. This is another major difference from bots that generate "all" possible moves for a particular position. Rat is only allowed to generate moves that belong to certain categories. Leaf nodes are evaluated only by a straightforward material evaluation to help avoid moves that lose material. This highly selective search looks, on average, at only 5 moves out of 5,000 to over 40,000 possible moves in a middle game position.

Trippen, Gerhard

213

Generalized Pattern Search Algorithm for Peptide Structure Prediction  

PubMed Central

Finding the near-native structure of a protein is one of the most important open problems in structural biology and biological physics. The problem becomes dramatically more difficult when a given protein has no regular secondary structure or it does not show a fold similar to structures already known. This situation occurs frequently when we need to predict the tertiary structure of small molecules, called peptides. In this research work, we propose a new ab initio algorithm, the generalized pattern search algorithm, based on the well-known class of Search-and-Poll algorithms. We performed an extensive set of simulations over a well-known set of 44 peptides to investigate the robustness and reliability of the proposed algorithm, and we compared the peptide conformation with a state-of-the-art algorithm for peptide structure prediction known as PEPstr. In particular, we tested the algorithm on the instances proposed by the originators of PEPstr, to validate the proposed algorithm; the experimental results confirm that the generalized pattern search algorithm outperforms PEPstr by 21.17% in terms of average root mean-square deviation, RMSD C?.

Nicosia, Giuseppe; Stracquadanio, Giovanni

2008-01-01

214

Platform for extraction, visualization and analysis of search trends  

Microsoft Academic Search

Currently available web search engines and social media websites stick to their specific web traffic trends and do not provide generic overview of the whole web. We can better understand the current market and user interest about a specific product or topic or any term by analyzing all the trends from search engines and social media. Unfortunately, there is no

Abdul Wahid; Boyan Bontchev

2010-01-01

215

Scanners and drillers: Characterizing expert visual search through volumetric images  

PubMed Central

Modern imaging methods like computed tomography (CT) generate 3-D volumes of image data. How do radiologists search through such images? Are certain strategies more efficient? Although there is a large literature devoted to understanding search in 2-D, relatively little is known about search in volumetric space. In recent years, with the ever-increasing popularity of volumetric medical imaging, this question has taken on increased importance as we try to understand, and ultimately reduce, errors in diagnostic radiology. In the current study, we asked 24 radiologists to search chest CTs for lung nodules that could indicate lung cancer. To search, radiologists scrolled up and down through a “stack” of 2-D chest CT “slices.” At each moment, we tracked eye movements in the 2-D image plane and coregistered eye position with the current slice. We used these data to create a 3-D representation of the eye movements through the image volume. Radiologists tended to follow one of two dominant search strategies: “drilling” and “scanning.” Drillers restrict eye movements to a small region of the lung while quickly scrolling through depth. Scanners move more slowly through depth and search an entire level of the lung before moving on to the next level in depth. Driller performance was superior to the scanners on a variety of metrics, including lung nodule detection rate, percentage of the lung covered, and the percentage of search errors where a nodule was never fixated.

Drew, Trafton; Vo, Melissa Le-Hoa; Olwal, Alex; Jacobson, Francine; Seltzer, Steven E.; Wolfe, Jeremy M.

2013-01-01

216

Priming of color and position during visual search in unilateral spatial neglect  

Microsoft Academic Search

We examined priming of visual search by repeated target location or color in two patients with left visual neglect and extinction, following strokes centered on the right inferior parietal lobe. Both patients, like the healthy controls we tested, showed intact priming, with performance speeded when either the location or color of a singleton target was repeated over successive trials in

A. Kristjansson; Patrik Vuilleumier; Paresh Malhotra; Masud Husain; Jon Driver

2005-01-01

217

A saliency-based search mechanism for overt and covert shifts of visual attention  

Microsoft Academic Search

Most models of visual search, whether involving overt eye movements or covert shifts of attention, are based on the concept of a saliency map, that is, an explicit two-dimensional map that encodes the saliency or conspicuity of objects in the visual environment. Competition among neurons in this map gives rise to a single winning location that corresponds to the next

Laurent Itti; Christof Koch

2000-01-01

218

The Effect of Rich Web Portal Design and Floating Animations on Visual Search  

Microsoft Academic Search

Unlike most Web portals in the world, Chinese Web portals are characterized by a huge amount of information, excessive visual stimuli, and very long Web pages. The objective of this study is to investigate the effect of such rich Web portal designs and floating animations on visual search, emphasizing a comparison between Chinese users and German users. Two experiments were

Pei-Luen Patrick Rau; Qin Gao; Jie Liu

2007-01-01

219

The role of object categories in hybrid visual and memory search.  

PubMed

In hybrid search, observers search for any of several possible targets in a visual display containing distracting items and, perhaps, a target. Wolfe (2012) found that response times (RTs) in such tasks increased linearly with increases in the number of items in the display. However, RT increased linearly with the log of the number of items in the memory set. In earlier work, all items in the memory set were unique instances (e.g., this apple in this pose). Typical real-world tasks involve more broadly defined sets of stimuli (e.g., any "apple" or, perhaps, "fruit"). The present experiments show how sets or categories of targets are handled in joint visual and memory search. In Experiment 1, searching for a digit among letters was not like searching for targets from a 10-item memory set, though searching for targets from an N-item memory set of arbitrary alphanumeric characters was like searching for targets from an N-item memory set of arbitrary objects. In Experiment 2, observers searched for any instance of N sets or categories held in memory. This hybrid search was harder than search for specific objects. However, memory search remained logarithmic. Experiment 3 illustrates the interaction of visual guidance and memory search when a subset of visual stimuli are drawn from a target category. Furthermore, we outline a conceptual model, supported by our results, defining the core components that would be necessary to support such categorical hybrid searches. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:24661054

Cunningham, Corbin A; Wolfe, Jeremy M

2014-08-01

220

Generalized pattern search algorithms with adaptive precision function evaluations  

SciTech Connect

In the literature on generalized pattern search algorithms, convergence to a stationary point of a once continuously differentiable cost function is established under the assumption that the cost function can be evaluated exactly. However, there is a large class of engineering problems where the numerical evaluation of the cost function involves the solution of systems of differential algebraic equations. Since the termination criteria of the numerical solvers often depend on the design parameters, computer code for solving these systems usually defines a numerical approximation to the cost function that is discontinuous with respect to the design parameters. Standard generalized pattern search algorithms have been applied heuristically to such problems, but no convergence properties have been stated. In this paper we extend a class of generalized pattern search algorithms to a form that uses adaptive precision approximations to the cost function. These numerical approximations need not define a continuous function. Our algorithms can be used for solving linearly constrained problems with cost functions that are at least locally Lipschitz continuous. Assuming that the cost function is smooth, we prove that our algorithms converge to a stationary point. Under the weaker assumption that the cost function is only locally Lipschitz continuous, we show that our algorithms converge to points at which the Clarke generalized directional derivatives are nonnegative in predefined directions. An important feature of our adaptive precision scheme is the use of coarse approximations in the early iterations, with the approximation precision controlled by a test. Such an approach leads to substantial time savings in minimizing computationally expensive functions.

Polak, Elijah; Wetter, Michael

2003-05-14

221

Harmony filter: A robust visual tracking system using the improved harmony search algorithm  

Microsoft Academic Search

In this article a novel approach to visual tracking called the harmony filter is presented. It is based on the Harmony Search algorithm, a derivative free meta-heuristic optimisation algorithm inspired by the way musicians improvise new harmonies. The harmony filter models the target as a colour histogram and searches for the best estimated target location using the Bhattacharyya coefficient as

Jaco Fourie; Steven Mills; Richard Green

2010-01-01

222

Age Differences in Visual Search for Traffic Signs During a Simulated Conversation  

Microsoft Academic Search

The effects of divided attention were examined in younger adults (M = 23 years) and older adults (M = 64 years) who searched for traffic signs in digitized images of traffic scenes. Sign search was executed under single-task and dual-task conditions in scenes containing either small or large amounts of visual clutter. For both age groups, clutter and the secondary

Lisa C. McPhee; Charles T. Scialfa; Wanda M. Dennis; Geoffrey Ho; Jeff K. Caird

2004-01-01

223

Serial and Parallel Attentive Visual Searches: Evidence from Cumulative Distribution Functions of Response Times  

ERIC Educational Resources Information Center

Participants searched a visual display for a target among distractors. Each of 3 experiments tested a condition proposed to require attention and for which certain models propose a serial search. Serial versus parallel processing was tested by examining effects on response time means and cumulative distribution functions. In 2 conditions, the…

Sung, Kyongje

2008-01-01

224

Brief Report: Eye Movements during Visual Search Tasks Indicate Enhanced Stimulus Discriminability in Subjects with PDD  

ERIC Educational Resources Information Center

Subjects with PDD excel on certain visuo-spatial tasks, amongst which visual search tasks, and this has been attributed to enhanced perceptual discrimination. However, an alternative explanation is that subjects with PDD show a different, more effective search strategy. The present study aimed to test both hypotheses, by measuring eye movements…

Kemner, Chantal; van Ewijk, Lizet; van Engeland, Herman; Hooge, Ignace

2008-01-01

225

Search Aid System Based on Machine Vision and Its Visual Attention Model for Rescue Target Detection  

Microsoft Academic Search

The prompt search and rescue of lifesaving target is very important in the case that a marine casualty occurs. To detect the small target in the wide views over the sea, we have proposed a machine vision system to aid search and rescue on the sea, which combines remote sensing, radar, infrared with visual light technology. One of the detection

Ran Xin; Ren Lei

2010-01-01

226

Visual Search Performance in the Autism Spectrum II: The Radial Frequency Search Task with Additional Segmentation Cues  

ERIC Educational Resources Information Center

The Embedded Figures Test (EFT) requires detecting a shape within a complex background and individuals with autism or high Autism-spectrum Quotient (AQ) scores are faster and more accurate on this task than controls. This research aimed to uncover the visual processes producing this difference. Previously we developed a search task using radial…

Almeida, Renita A.; Dickinson, J. Edwin; Maybery, Murray T.; Badcock, Johanna C.; Badcock, David R.

2010-01-01

227

Subset-Selectivity and Distractor Matching in Visual Conjunction Search.  

National Technical Information Service (NTIS)

In search for a conjunction of color and orientation, Theeuwes, Kaptein and Van der Heijden (1993) obtained target absent responses that were in some conditions faster and in other conditions slower than target present responses. In addition, target absen...

N. A. Kaptein J. Theeuwes

1994-01-01

228

APPLICATION OF PATTERN SEARCH METHOD TO POWER SYSTEM ECONOMIC LOAD DISPATCH  

Microsoft Academic Search

Direct Search (DS) methods are evolutionary algorithms used to solve constrained optimization problems. DS methods do not require information about the gradient of the objective function while searching for an optimum solution. One of such methods is Pattern Search (PS) algorithm. This study examines the usefulness of a constrained pattern search algorithm to solve well-known power system Economic Load Dispatch

J S Alsumait; J K Sykulski; A K Alothman

229

Application of pattern search method to power system valve-point economic load dispatch  

Microsoft Academic Search

Direct search (DS) methods are evolutionary algorithms used to solve constrained optimization problems. DS methods do not require any information about the gradient of the objective function at hand, while searching for an optimum solution. One of such methods is pattern search (PS) algorithm. This study presents a new approach based on a constrained pattern search algorithm to solve well-known

J. S. Al-Sumait; A. K. AL-Othman; J. K. Sykulski

2007-01-01

230

What are the Shapes of Response Time Distributions in Visual Search?  

PubMed Central

Many visual search experiments measure reaction time (RT) as their primary dependent variable. Analyses typically focus on mean (or median) RT. However, given enough data, the RT distribution can be a rich source of information. For this paper, we collected about 500 trials per cell per observer for both target-present and target-absent displays in each of three classic search tasks: feature search, with the target defined by color; conjunction search, with the target defined by both color and orientation; and spatial configuration search for a 2 among distractor 5s. This large data set allows us to characterize the RT distributions in detail. We present the raw RT distributions and fit several psychologically motivated functions (ex-Gaussian, ex-Wald, Gamma, and Weibull) to the data. We analyze and interpret parameter trends from these four functions within the context of theories of visual search.

Palmer, Evan M.; Horowitz, Todd S.; Torralba, Antonio; Wolfe, Jeremy M.

2011-01-01

231

Visualization Methods for Personal Photo Collections: Browsing and Searching in the PhotoFinder  

Microsoft Academic Search

Software tools for personal photo collection management are proliferating, but they usually have limited searching and browsing functions. We implemented the PhotoFinder prototype to enable non-technical users of personal photo collections to search and browse easily. PhotoFinder provides a set of visual Boolean query interfaces, coupled with dynamic query and query preview features. It gives users powerful search capabilities. Using

Hyunmo Kang; Ben Shneiderman

2000-01-01

232

Approximate Recursive Bayesian Filtering methods for robot visual search  

Microsoft Academic Search

Visual servoing is an essential enabling technology for robots operating in semi- and un-structured contexts, such as robot assistants working in collaboration with people. However, due to dynamic and unpredictable nature of such environments, existing methods of target tracking can lose visibility of task\\/target, leading to servo failure. In such situations, it is desirable that the robot reacquire the target

Sina Radmard; Elizabeth A. Croft

2011-01-01

233

Searching for Meaning: Visual Culture from an Anthropological Perspective  

ERIC Educational Resources Information Center

In this article, the author discusses the importance of Viktor Lowenfeld's influence on her research, describes visual anthropology, gives examples of her research, and examines the implications of this type of research for teachers. The author regards Lowenfeld's (1952/1939) early work with children in Austria as a form of participant observation…

Stokrocki, Mary

2006-01-01

234

Effects of contour enhancement on low-vision preference and visual search  

PubMed Central

PURPOSE To determine whether image enhancement improves visual search performance and whether enhanced images were also preferred by subjects with vision impairment. METHOD Subjects (n=24) with vision impairment (vision: 20/52 to 20/240) completed visual search and preference tasks for 150 static images that were enhanced to increase object contours’ visual saliency. Subjects were divided into two groups and were shown three enhancement levels. Original and Medium enhancement were shown to both groups. High enhancement was shown to Group 1 and Low was shown to Group 2. For search, subjects pointed to an object that matched a search target displayed at the top left of the screen. An “integrated search performance” measure (area under the curve of cumulative correct response rate over search time) quantified performance. For preference, subjects indicated the preferred side when viewing the same image with different enhancement levels on side-by-side HDTVs. RESULTS Contour enhancement did not improve performance in the visual search task. Group 1 subjects significantly (p<0.001) rejected the High enhancement, and showed no preference for Medium enhancement over the Original images. Group 2 subjects significantly preferred (p<0.001) both the Medium and the Low enhancement levels over Original. Contrast sensitivity was correlated with both preference and performance; subjects with worse contrast sensitivity performed worse in the search task (?=0.77, p<0.001) and preferred more enhancement (?=?0.47, p=0.02). No correlation between visual search performance and enhancement preference was found. However, a small group of subjects (n=6) in a narrow range of mid-contrast sensitivity performed better with the enhancement and most (n=5) also preferred the enhancement. CONCLUSIONS Preferences for image enhancement can be dissociated from search performance in people with vision impairment. Further investigations are needed to study the relationships between preference and performance for a narrow range of mid-contrast sensitivity where a beneficial effect of enhancement may exist.

Satgunam, PremNandhini; Woods, Russell L; Luo, Gang; Bronstad, P Matthew; Reynolds, Zachary; Ramachandra, Chaithanya; Mel, Bartlett W.; Peli, Eli

2012-01-01

235

Use of an augmented-vision device for visual search by patients with tunnel vision  

PubMed Central

Purpose To study the effect of an augmented-vision device that superimposes minified contour images over natural vision on visual search performance of patients with tunnel vision. Methods Twelve subjects with tunnel vision searched for targets presented outside their visual fields (VF) on a blank background under three cue conditions (with contour cues provided by the device, with auditory cues, and without cues). Three subjects (VF: 8º to 11º wide) carried out the search over a 90º×74º area, and nine subjects (VF: 7º to 16º wide) over a 66º×52º area. Eye and head movements were recorded for performance analyses that included directness of search path, search time, and gaze speed. Results Directness of the search path was greatly and significantly improved when the contour or auditory cues were provided in both the larger and smaller area search. When using the device, a significant reduction in search time (28%~74%) was demonstrated by all 3 subjects in the larger area search and by subjects with VF wider than 10º in the smaller area search (average 22%). Directness and the gaze speed accounted for 90% of the variability of search time. Conclusions While performance improvement with the device for the larger search area was obvious, whether it was helpful for the smaller search area depended on VF and gaze speed. As improvement in directness was demonstrated, increased gaze speed, which could result from further training and adaptation to the device, might enable patients with small VFs to benefit from the device for visual search tasks.

Luo, Gang; Peli, Eli

2006-01-01

236

Effects of targets embedded within words in a visual search task  

PubMed Central

Visual search performance can be negatively affected when both targets and distracters share a dimension relevant to the task. This study examined if visual search performance would be influenced by distracters that affect a dimension irrelevant from the task. In Experiment 1 within the letter string of a letter search task, target letters were embedded within a word. Experiment 2 compared targets embedded in words to targets embedded in nonwords. Experiment 3 compared targets embedded in words to a condition in which a word was present in a letter string, but the target letter, although in the letter string, was not embedded within the word. The results showed that visual search performance was negatively affected when a target appeared within a high frequency word. These results suggest that the interaction and effectiveness of distracters is not merely dependent upon common features of the target and distracters, but can be affected by word frequency (a dimension not related to the task demands).

Grabbe, Jeremy W.

2014-01-01

237

Visual Servoing: A technology in search of an application  

SciTech Connect

Considerable research has been performed on Robotic Visual Servoing (RVS) over the past decade. Using real-time visual feedback, researchers have demonstrated that robotic systems can pick up moving parts, insert bolts, apply sealant, and guide vehicles. With the rapid improvements being made in computing and image processing hardware, one would expect that every robot manufacturer would have a RVS option by the end of the 1990s. So why aren`t the Fanucs, ABBs, Adepts, and Motomans of the world investing heavily in RVS? I would suggest four seasons: cost, complexity, reliability, and lack of demand. Solutions to the first three are approaching the point where RVS could be commercially available; however, the lack of demand is keeping RVS from becoming a reality in the near future. A new set of applications is needed to focus near term RVS development. These must be applications which currently do not have solutions. Once developed and working in one application area, the technology is more likely to quickly spread to other areas. DOE has several applications that are looking for technological solutions, such as agile weapons production, weapons disassembly, decontamination and dismantlement of nuclear facilities, and hazardous waste remediation. This paper will examine a few of these areas and suggest directions for application-driven visual servoing research.

Feddema, J.T.

1994-05-01

238

Training Older Adults to Search More Effectively: Scanning Strategy and Visual Search in Dynamic Displays  

Microsoft Academic Search

The authors examined the ability of older adults to modify their search strategies to detect changes in dynamic displays. Older adults who made few eye movements during search (i.e., covert searchers) were faster and more accurate compared with individuals who made many eye movements (i.e., overt searchers). When overt searchers were instructed to adopt a covert search strategy, target detection

Ensar Becic; Walter R. Boot; Arthur F. Kramer

2008-01-01

239

Visualizing Document Classification: A Search Aid for the Digital Library.  

ERIC Educational Resources Information Center

Discusses access to digital libraries on the World Wide Web via Web browsers and describes the design of a language-independent document classification system to help users of the Florida Center for Library Automation analyze search query results. Highlights include similarity scores, clustering, graphical representation of document similarity,…

Lieu, Yew-Huey; Dantzig, Paul; Sachs, Martin; Corey, James T.; Hinnebusch, Mark T.; Damashek, Marc; Cohen, Jonathan

2000-01-01

240

A ground-like surface facilitates visual search in chimpanzees (Pan troglodytes)  

PubMed Central

Ground surfaces play an important role in terrestrial species' locomotion and ability to manipulate objects. In humans, ground surfaces have been found to offer significant advantages in distance perception and visual-search tasks (“ground dominance”). The present study used a comparative perspective to investigate the ground-dominance effect in chimpanzees, a species that spends time both on the ground and in trees. During the experiments chimpanzees and humans engaged in a search for a cube on a computer screen; the target cube was darker than other cubes. The search items were arranged on a ground-like or ceiling-like surface, which was defined by texture gradients and shading. The findings indicate that a ground-like, but not a ceiling-like, surface facilitated the search for a difference in luminance among both chimpanzees and humans. Our findings suggest the operation of a ground-dominance effect on visual search in both species.

Imura, Tomoko; Tomonaga, Masaki

2013-01-01

241

The Visual Hemifield Asymmetry in the Spatial Blink during Singleton Search and Feature Search  

ERIC Educational Resources Information Center

The present study examined a visual field asymmetry in the contingent capture of attention that was previously observed by Du and Abrams (2010). In our first experiment, color singleton distractors that matched the color of a to-be-detected target produced a stronger capture of attention when they appeared in the left visual hemifield than in the…

Burnham, Bryan R.; Rozell, Cassandra A.; Kasper, Alex; Bianco, Nicole E.; Delliturri, Antony

2011-01-01

242

Serial, Covert Shifts of Attention during Visual Search Are Reflected by the Frontal Eye Fields and Correlated with Population Oscillations  

Microsoft Academic Search

SUMMARY Attention regulates the flood of sensory information into a manageable stream, and so understanding howattentioniscontrollediscentraltounderstanding cognition. Competing theories suggest visual search involves serial and\\/or parallel allocation of attention, but there is little direct, neural evidence for either mechanism. Two monkeys were trained to covertly search an array for a target stimulus under visual search (endogenous) and pop-out (exogenous) con-

Timothy J. Buschman; Earl K. Miller

2009-01-01

243

Playing shooter and driving videogames improves top-down guidance in visual search.  

PubMed

Playing action videogames is known to improve visual spatial attention and related skills. Here, we showed that playing action videogames also improves classic visual search, as well as the ability to locate targets in a dual search that mimics certain aspects of an action videogame. In Experiment 1A, first-person shooter (FPS) videogame players were faster than nonplayers in both feature search and conjunction search, and in Experiment 1B, they were faster and more accurate in a peripheral search and identification task while simultaneously performing a central search. In Experiment 2, we showed that 10 h of play could improve the performance of nonplayers on each of these tasks. Three different genres of videogames were used for training: two action games and a 3-D puzzle game. Participants who played an action game (either an FPS or a driving game) achieved greater gains on all search tasks than did those who trained using the puzzle game. Feature searches were faster after playing an action videogame, suggesting that players developed a better target template to guide search in a top-down manner. The results of the dual search suggest that, in addition to enhancing the ability to divide attention, playing an action game improves the top-down guidance of attention to possible target locations. The results have practical implications for the development of training tools to improve perceptual and cognitive skills. PMID:23460295

Wu, Sijing; Spence, Ian

2013-05-01

244

CiteSpace II: Detecting and visualizing emerging trends and transient patterns in scientific literature  

Microsoft Academic Search

This article describes the latest development of a generic approach to detecting and visualizing emerging trends and transient patterns in scientific literature. The work makes substantial theoretical and methodological contributions to progressive knowledge domain visualization. A specialty is conceptualized and visualized as a time-variant duality between two fundamental concepts in information science - research fronts and intellectual bases. A research

Chaomei Chen

2006-01-01

245

Mouse visual neocortex supports multiple stereotyped patterns of microcircuit activity.  

PubMed

Spiking correlations between neocortical neurons provide insight into the underlying synaptic connectivity that defines cortical microcircuitry. Here, using two-photon calcium fluorescence imaging, we observed the simultaneous dynamics of hundreds of neurons in slices of mouse primary visual cortex (V1). Consistent with a balance of excitation and inhibition, V1 dynamics were characterized by a linear scaling between firing rate and circuit size. Using lagged firing correlations between neurons, we generated functional wiring diagrams to evaluate the topological features of V1 microcircuitry. We found that circuit connectivity exhibited both cyclic graph motifs, indicating recurrent wiring, and acyclic graph motifs, indicating feedforward wiring. After overlaying the functional wiring diagrams onto the imaged field of view, we found properties consistent with Rentian scaling: wiring diagrams were topologically efficient because they minimized wiring with a modular architecture. Within single imaged fields of view, V1 contained multiple discrete circuits that were overlapping and highly interdigitated but were still distinct from one another. The majority of neurons that were shared between circuits displayed peri-event spiking activity whose timing was specific to the active circuit, whereas spike times for a smaller percentage of neurons were invariant to circuit identity. These data provide evidence that V1 microcircuitry exhibits balanced dynamics, is efficiently arranged in anatomical space, and is capable of supporting a diversity of multineuron spike firing patterns from overlapping sets of neurons. PMID:24899701

Sadovsky, Alexander J; MacLean, Jason N

2014-06-01

246

A pyramidal neural network for visual pattern recognition.  

PubMed

In this paper, we propose a new neural architecture for classification of visual patterns that is motivated by the two concepts of image pyramids and local receptive fields. The new architecture, called pyramidal neural network (PyraNet), has a hierarchical structure with two types of processing layers: Pyramidal layers and one-dimensional (1-D) layers. In the new network, nonlinear two-dimensional (2-D) neurons are trained to perform both image feature extraction and dimensionality reduction. We present and analyze five training methods for PyraNet [gradient descent (GD), gradient descent with momentum, resilient back-propagation (RPROP), Polak-Ribiere conjugate gradient (CG), and Levenberg-Marquadrt (LM)] and two choices of error functions [mean-square-error (mse) and cross-entropy (CE)]. In this paper, we apply PyraNet to determine gender from a facial image, and compare its performance on the standard facial recognition technology (FERET) database with three classifiers: The convolutional neural network (NN), the k-nearest neighbor (k-NN), and the support vector machine (SVM). PMID:17385623

Phung, Son Lam; Bouzerdoum, Abdesselam

2007-03-01

247

Visual Scan Patterns During Simulated Control of an Uninhabited Aerial Vehicle (UAV)  

Microsoft Academic Search

TVARYANAS AP. Visual scan patterns during simulated control of an uninhabited aerial vehicle (UAV). Aviat Space Environ Med 2004; 75:531- 8. Background: This study investigated pilots' visual scan patterns on an uninhabited aerial vehicle (UAV) flight display that used moving textbox symbology to emulate vertical moving pointers for the primary flight instruments. Methods: Eye tracking measurements were recorded for five

Anthony P. Tvaryanas

2004-01-01

248

The Nature and Process of Development in Averaged Visually Evoked Potentials: Discussion on Pattern Structure.  

ERIC Educational Resources Information Center

This paper examines the development of visually evoked EEG patterns in retarded and normal subjects. The paper focuses on the averaged visually evoked potentials (AVEP) in the central and occipital regions of the brain in eyes closed and eyes open conditions. Wave pattern, amplitude, and latency are examined. The first section of the paper reviews…

Izawa, Shuji; Mizutani, Tohru

249

Target features and target-distractor relation are both primed in visual search.  

PubMed

Intertrial priming in visual search is the finding that repeating target and distractor features from one trial to the next speeds up search, relative to when these features change. Recently, Becker (2008) reported evidence that it is not so much the repetition of absolute feature values that causes priming, but repetition of the relation between target and distractors. For example, in search for a unique size, the size of the search elements may change from trial to trial, but this does not hurt performance as long as the target remains consistently larger (or smaller) than the distractors. Becker (2008) concluded that such findings are difficult to reconcile with existing theory. Here, we replicate the findings in the dimensions of size, color, and luminance and show that these effects are not due to the magnitude of feature changes or to search strategies, as may be induced by blocking versus mixing different types of intertrial changes experienced by observers. However, we show that repeating a feature from one trial to the next does convey a benefit above and beyond repeating the target-distractor relation. We argue that both effects can be readily accounted for within current models of visual search. Priming of relations results when one assumes the existence of cardinal feature channels, as do most models of visual search. Additional priming of specific values results when one assumes broadly distributed, overlapping feature channels. PMID:24415176

Meeter, Martijn; Olivers, Christian N L

2014-04-01

250

Pattern-driven neighborhood search for biclustering of microarray data  

PubMed Central

Background Biclustering aims at finding subgroups of genes that show highly correlated behaviors across a subgroup of conditions. Biclustering is a very useful tool for mining microarray data and has various practical applications. From a computational point of view, biclustering is a highly combinatorial search problem and can be solved with optimization methods. Results We describe a stochastic pattern-driven neighborhood search algorithm for the biclustering problem. Starting from an initial bicluster, the proposed method improves progressively the quality of the bicluster by adjusting some genes and conditions. The adjustments are based on the quality of each gene and condition with respect to the bicluster and the initial data matrix. The performance of the method was evaluated on two well-known microarray datasets (Yeast cell cycle and Saccharomyces cerevisiae), showing that it is able to obtain statistically and biologically significant biclusters. The proposed method was also compared with six reference methods from the literature. Conclusions The proposed method is computationally fast and can be applied to discover significant biclusters. It can also used to effectively improve the quality of existing biclusters provided by other biclustering methods.

2012-01-01

251

A Visual Perceiving and Eyeball-Motion Controlling Neural Network for Object Searching and Locating  

Microsoft Academic Search

This paper proposes a visual cognitive neural network for automatic object searching and locating. The model consists of two sub-networks. One is a visual perceiving network, which simulates human eyes to input image signals and recognize an object's direction and distance in terms of a high-level perceiving neuron's maximum response. The other one is an eyeball-motion controlling network, which simulates

Jun Miao; Xilin Chen; Wen Gao; Yiqiang Chen

2006-01-01

252

Quantifying the performance limits of human saccadic targeting during visual search  

NASA Technical Reports Server (NTRS)

In previous studies of saccadic targeting, the issue how visually guided saccades to unambiguous targets are programmed and executed has been examined. These studies have found different degrees of guidance for saccades depending on the task and task difficulty. In this study, we use ideal-observer analysis to estimate the visual information used for the first saccade during a search for a target disk in noise. We quantitatively compare the performance of the first saccadic decision to that of the ideal observer (ie absolute efficiency of the first saccade) and to that of the associated final perceptual decision at the end of the search (ie relative efficiency of the first saccade). Our results show, first, that at all levels of salience tested, the first saccade is based on visual information from the stimulus display, and its highest absolute efficiency is approximately 20%. Second, the efficiency of the first saccade is lower than that of the final perceptual decision after active search (with eye movements) and has a minimum relative efficiency of 19% at the lowest level of saliency investigated. Third, we found that requiring observers to maintain central fixation (no saccades allowed) decreased the absolute efficiency of their perceptual decision by up to a factor of two, but that the magnitude of this effect depended on target salience. Our results demonstrate that ideal-observer analysis can be extended to measure the visual information mediating saccadic target-selection decisions during visual search, which enables direct comparison of saccadic and perceptual efficiencies.

Eckstein, M. P.; Beutter, B. R.; Stone, L. S.

2001-01-01

253

Emotional priming of pop-out in visual search.  

PubMed

When searching for a discrepant target along a simple dimension such as color or shape, repetition of the target feature substantially speeds search, an effect known as feature priming of pop-out (V. Maljkovic and K. Nakayama, 1994). The authors present the first report of emotional priming of pop-out. Participants had to detect the face displaying a discrepant expression of emotion in an array of four face photographs. On each trial, the target when present was either a neutral face among emotional faces (angry in Experiment 1 or happy in Experiment 2), or an emotional face among neutral faces. Target detection was faster when the target displayed the same emotion on successive trials. This effect occurred for angry and for happy faces, not for neutral faces. It was completely abolished when faces were inverted instead of upright, suggesting that emotional categories rather than physical feature properties drive emotional priming of pop-out. The implications of the present findings for theoretical accounts of intertrial priming and for the face-in-the-crowd phenomenon are discussed. PMID:18410189

Lamy, Dominique; Amunts, Liana; Bar-Haim, Yair

2008-04-01

254

Markov Models of Search State Patterns in a Hypertext Information Retrieval System.  

ERIC Educational Resources Information Center

Describes research that was conducted to determine the search state patterns through which users retrieve information in hypertext systems. Use of the Markov model to describe users' search behavior is discussed, and search patterns of different user groups were studied by comparing transition probability matrices. (Contains 25 references.) (LRW)

Qiu, Liwen

1993-01-01

255

Disturbance of visual search by stimulating to posterior parietal cortex in the brain using transcranial magnetic stimulation  

NASA Astrophysics Data System (ADS)

In this study, we applied a transcranial magnetic stimulation (TMS) to investigate the temporal aspect for the functional processing of visual attention. Although it has been known that right posterior parietal cortex (PPC) in the brain has a role in certain visual search tasks, there is little knowledge about the temporal aspect of this area. Three visual search tasks that have different difficulties of task execution individually were carried out. These three visual search tasks are the ``easy feature task,'' the ``hard feature task,'' and the ``conjunction task.'' To investigate the temporal aspect of the PPC involved in the visual search, we applied various stimulus onset asynchronies (SOAs) and measured the reaction time of the visual search. The magnetic stimulation was applied on the right PPC or the left PPC by the figure-eight coil. The results show that the reaction times of the hard feature task are longer than those of the easy feature task. When SOA=150 ms, compared with no-TMS condition, there was a significant increase in target-present reaction time when TMS pulses were applied. We considered that the right PPC was involved in the visual search at about SOA=150 ms after visual stimulus presentation. The magnetic stimulation to the right PPC disturbed the processing of the visual search. However, the magnetic stimulation to the left PPC gives no effect on the processing of the visual search.

Iramina, Keiji; Ge, Sheng; Hyodo, Akira; Hayami, Takehito; Ueno, Shoogo

2009-04-01

256

Eye Movements, Visual Search and Scene Memory, in an Immersive Virtual Environment  

PubMed Central

Visual memory has been demonstrated to play a role in both visual search and attentional prioritization in natural scenes. However, it has been studied predominantly in experimental paradigms using multiple two-dimensional images. Natural experience, however, entails prolonged immersion in a limited number of three-dimensional environments. The goal of the present experiment was to recreate circumstances comparable to natural visual experience in order to evaluate the role of scene memory in guiding eye movements in a natural environment. Subjects performed a continuous visual-search task within an immersive virtual-reality environment over three days. We found that, similar to two-dimensional contexts, viewers rapidly learn the location of objects in the environment over time, and use spatial memory to guide search. Incidental fixations did not provide obvious benefit to subsequent search, suggesting that semantic contextual cues may often be just as efficient, or that many incidentally fixated items are not held in memory in the absence of a specific task. On the third day of the experience in the environment, previous search items changed in color. These items were fixated upon with increased probability relative to control objects, suggesting that memory-guided prioritization (or Surprise) may be a robust mechanisms for attracting gaze to novel features of natural environments, in addition to task factors and simple spatial saliency.

Sullivan, Brian; Snyder, Kat; Ballard, Dana; Hayhoe, Mary

2014-01-01

257

Detection of shape orientation depends on salient axes of symmetry and elongation: Evidence from visual search  

Microsoft Academic Search

Three experiments investigated the role of the global spatial structure of two-dimensional (2-D) shapes in terms of symmetry\\u000a and elongation on visual search for shape orientation. Experiment 1 demonstrated the often reported orientation search asymmetry\\u000a (i.e., a faster detection of a tilted target among vertical distractors than the reverse) for the global orientation of 2-D\\u000a polygons that possess a salient,

Luc Boutsen; Christian Marendaz

2001-01-01

258

Visual search for a target changing in synchrony with an auditory signal  

PubMed Central

We examined whether the detection of audio–visual temporal synchrony is determined by a pre-attentive parallel process, or by an attentive serial process using a visual search paradigm. We found that detection of a visual target that changed in synchrony with an auditory stimulus was gradually impaired as the number of unsynchronized visual distractors increased (experiment 1), whereas synchrony discrimination of an attended target in a pre-cued location was unaffected by the presence of distractors (experiment 2). The effect of distractors cannot be ascribed to reduced target visibility nor can the increase in false alarm rates be predicted by a noisy parallel processing model. Reaction times for target detection increased linearly with number of distractors, with the slope being about twice as steep for target-absent trials as for target-present trials (experiment 3). Similar results were obtained regardless of whether the audio–visual stimulus consisted of visual flashes synchronized with amplitude-modulated pips, or of visual rotations synchronized with frequency-modulated up–down sweeps. All of the results indicate that audio–visual perceptual synchrony is judged by a serial process and are consistent with the suggestion that audio–visual temporal synchrony is detected by a ‘mid-level’ feature matching process.

Fujisaki, Waka; Koene, Ansgar; Arnold, Derek; Johnston, Alan; Nishida, Shin'ya

2005-01-01

259

Adaptation of video game UVW mapping to 3D visualization of gene expression patterns  

NASA Astrophysics Data System (ADS)

Analysis of gene expression patterns within an organism plays a critical role in associating genes with biological processes in both health and disease. During embryonic development the analysis and comparison of different gene expression patterns allows biologists to identify candidate genes that may regulate the formation of normal tissues and organs and to search for genes associated with congenital diseases. No two individual embryos, or organs, are exactly the same shape or size so comparing spatial gene expression in one embryo to that in another is difficult. We will present our efforts in comparing gene expression data collected using both volumetric and projection approaches. Volumetric data is highly accurate but difficult to process and compare. Projection methods use UV mapping to align texture maps to standardized spatial frameworks. This approach is less accurate but is very rapid and requires very little processing. We have built a database of over 180 3D models depicting gene expression patterns mapped onto the surface of spline based embryo models. Gene expression data in different models can easily be compared to determine common regions of activity. Visualization software, both Java and OpenGL optimized for viewing 3D gene expression data will also be demonstrated.

Vize, Peter D.; Gerth, Victor E.

2007-01-01

260

Memory for found targets interferes with subsequent performance in multiple-target visual search.  

PubMed

Multiple-target visual searches--when more than 1 target can appear in a given search display--are commonplace in radiology, airport security screening, and the military. Whereas 1 target is often found accurately, additional targets are more likely to be missed in multiple-target searches. To better understand this decrement in 2nd-target detection, here we examined 2 potential forms of interference that can arise from finding a 1st target: interference from the perceptual salience of the 1st target (a now highly relevant distractor in a known location) and interference from a newly created memory representation for the 1st target. Here, we found that removing found targets from the display or making them salient and easily segregated color singletons improved subsequent search accuracy. However, replacing found targets with random distractor items did not improve subsequent search accuracy. Removing and highlighting found targets likely reduced both a target's visual salience and its memory load, whereas replacing a target removed its visual salience but not its representation in memory. Collectively, the current experiments suggest that the working memory load of a found target has a larger effect on subsequent search accuracy than does its perceptual salience. PMID:23163788

Cain, Matthew S; Mitroff, Stephen R

2013-10-01

261

Correlation of pattern reversal visual evoked potential parameters with the pattern standard deviation in primary open angle glaucoma  

PubMed Central

AIM To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation (PSD) of Humphrey visual field could be associated with visual evoked potential (VEP) parameters of patients having primary open angle glaucoma (POAG). METHODS Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential (PRVEP) were assessed in 100 patients with POAG. The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated (full field) and displayed on VEP monitor (colour 14?) by an electronic pattern regenerator inbuilt in an evoked potential recorder (RMS EMG EP MARK II). RESULTS The results of our study indicate that there is a highly significant (P<0.001) negative correlation of P100 amplitude and a statistically significant (P<0.05) positive correlation of N70 latency, P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student's t-test. CONCLUSION Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values. Conversely, as PSD increases the magnitude of VEP excursions were found to be diminished.

Kothari, Ruchi; Bokariya, Pradeep; Singh, Ramji; Singh, Smita; Narang, Purvasha

2014-01-01

262

Masked target transform volume clutter metric for human observer visual search modeling  

Microsoft Academic Search

The Night Vision and Electronic Sensors Directorate (NVESD) develops an imaging system performance model to aid in the design and comparison of imaging systems for military use. It is intended to approximate visual task performance for a typical human observer with an imaging system of specified optical, electrical, physical, and environmental parameters. When modeling search performance, the model currently uses

Richard Kirk Moore

2009-01-01

263

The effect of midazolam on visual search: Implications for understanding amnesia  

Microsoft Academic Search

The notion of multiple memory systems based on conscious accessibility has been supported largely by neuropsychological patient studies. Specifically, it was widely held that amnesic patients have impaired explicit memory performance but spared implicit memory performance. However, recent patient studies have called the implicit\\/explicit memory distinction into question. In this study, normal participants were tested on a visual search task,

Joseph Quinlan; Edward Thornton; Lynne M. Reder

2004-01-01

264

The effects of link format and screen location on visual search of web pages  

Microsoft Academic Search

Navigation of web pages is of critical importance to the usability of web-based systems such as the World Wide Web and intranets. The primary means of navigation is through the use of hyperlinks. However, few studies have examined the impact of the presentation format of these links on visual search. The present study used a two-factor mixed measures design to

Jonathan Ling; Paul van Schaik

2004-01-01

265

Visual Search for Traffic Signs: The Effects of Clutter, Luminance, and Aging  

Microsoft Academic Search

Latency and eye movement measures were used to examine the effects of aging, clutter, and luminance on visual search for traffic signs embedded in digitized images of driving scenes. Initially 14 older and 14 younger observers classified daytime and nighttime traffic scenes as containing low or high amounts of clutter. Next, an independent sample of 14 younger and 14 older

Geoffrey Ho; Charles T. Scialfa; Jeff K. Caird; Trevor Graw

2001-01-01

266

A test of economic models of stopping policy in visual search  

Microsoft Academic Search

Optimization models of human visual search performance can be constructed that assume that the human operator maximizes an objective function, subject to given constraints. Two experiments were performed to validate one such optimization model, using ten students as the subjects. They were instructed to inspect printed circuit boards for one or two faults under different defective rates and cost structures.It

C. G. DRURY; CHIA-FEN CHI

1995-01-01

267

Eye movements and attention in reading, scene perception, and visual search  

Microsoft Academic Search

Eye movements are now widely used to investigate cognitive processes during reading, scene perception, and visual search. In this article, research on the following topics is reviewed with respect to reading: (a) the perceptual span (or span of effective vision), (b) preview benefit, (c) eye movement control, and (d) models of eye movements. Related issues with respect to eye movements

Keith Rayner

2009-01-01

268

Low Target Prevalence Is a Stubborn Source of Errors in Visual Search Tasks  

ERIC Educational Resources Information Center

In visual search tasks, observers look for targets in displays containing distractors. Likelihood that targets will be missed varies with target prevalence, the frequency with which targets are presented across trials. Miss error rates are much higher at low target prevalence (1%-2%) than at high prevalence (50%). Unfortunately, low prevalence is…

Wolfe, Jeremy M.; Horowitz, Todd S.; Van Wert, Michael J.; Kenner, Naomi M.; Place, Skyler S.; Kibbi, Nour

2007-01-01

269

How You Move Is What You See: Action Planning Biases Selection in Visual Search  

ERIC Educational Resources Information Center

Three experiments investigated the impact of planning and preparing a manual grasping or pointing movement on feature detection in a visual search task. The authors hypothesized that action planning may prime perceptual dimensions that provide information for the open parameters of that action. Indeed, preparing for grasping facilitated detection…

Wykowska, Agnieszka; Schubo, Anna; Hommel, Bernhard

2009-01-01

270

Visual Keyword Image Retrieval Based on Synergetic Neural Network for Web-Based Image Search  

Microsoft Academic Search

Feature extraction and similarity measure are two basickey issues in image retrieval. Combining the advantages of SNNin image recognition and selective attention for image retrieval,a novel visual keywords-driven image retrieval approach basedon these properties has been proposed. By using a predefinedset of visual keywords as prototype patterns stored with theSNN and then measuring the degree of similiarity of the storedimages

Tong Zhao; Lilian H. Tang; Horace H. S. Ip; Feihu Qi

2001-01-01

271

A Globally Convergent Augmented Lagrangian Pattern Search Algorithm for Optimization with General Constraints and Simple Bounds  

Microsoft Academic Search

We give a pattern search methodfor nonlinearly constrainedoptimization that is an ad aption of a boundconstrainedaugmentedLagrangian methodfirst proposedby Conn, Gould , andToint ( SIAM J. Numer. Anal., 28 (1991), pp. 545-572). In the pattern search adaptation, we solve the boundconstrainedsubproblem approximately using a pattern search method. The stopping criterion proposedby Conn, Gould , andToint for the solution of the subproblem

Robert Michael Lewis; Virginia Torczon

2002-01-01

272

Searching for a major locus for male pattern baldness (MPB)  

SciTech Connect

Male pattern baldness (MPB) is a common trait in post-pubertal males. Approximately 50% of adult males present some degree of MPB by age 50. According to the classification provided by Hamilton in 1951 and modified by Norwood in 1975, the trait itself is a continuum that ranges from mild (Type I) to severe (Type VII) cases. In addition, there is extensive variability for the age of onset. The role of androgens in allowing the expression of this trait in males has been well established. This phenotype is uncommonly expressed in females. The high prevalence of the trait, the distribution of MPB as a continuous trait, and several non-allelic mutations identified in the mouse capable of affecting hair pattern, suggest that MPB is genetically heterogeneous. In order to reduce the probability of multiple non-allelic MPB genes within a pedigree, we selected 9 families in which MPB appears to segregate exclusively through the paternal lineage as compared to bilineal pedigrees. There are 32 males expressing this phenotype and females are treated as phenotype unknown. In general, affected individuals expressed the trait before 30 years of age with a severity of at least Type III or IV. We assumed an autosomal dominant model, with a gene frequency of 1/20 for the affected allele, and 90% penetrance. Simulation studies using the SLINK program with these pedigrees showed that these families would be sufficient to detect linkage under the assumption of a single major locus. If heterogeneity is present, the current resource does not have sufficient power to detect linkage at a statistically significant level, although candidate regions of the genome could be identified for further studies with additional pedigrees. Using 53 highly informative microsatellite markers, and a subset of 7 families, we have screened 30% of the genome. This search included several regions where candidate genes for MPB are located.

Anker, R.; Eisen, A.Z.; Donis-Keller, H. [Washington Univ. School of Medicine, St. Louis, MO (United States)

1994-09-01

273

Centre-of-Gravity Fixations in Visual Search: When Looking at Nothing Helps to Find Something  

PubMed Central

In visual search, some fixations are made between stimuli on empty regions, commonly referred to as “centre-of-gravity” fixations (henceforth: COG fixations). Previous studies have shown that observers with task expertise show more COG fixations than novices. This led to the view that COG fixations reflect simultaneous encoding of multiple stimuli, allowing more efficient processing of task-related items. The present study tested whether COG fixations also aid performance in visual search tasks with unfamiliar and abstract stimuli. Moreover, to provide evidence for the multiple-item processing view, we analysed the effects of COG fixations on the number and dwell times of stimulus fixations. The results showed that (1) search efficiency increased with increasing COG fixations even in search for unfamiliar stimuli and in the absence of special higher-order skills, (2) COG fixations reliably reduced the number of stimulus fixations and their dwell times, indicating processing of multiple distractors, and (3) the proportion of COG fixations was dynamically adapted to potential information gain of COG locations. A second experiment showed that COG fixations are diminished when stimulus positions unpredictably vary across trials. Together, the results support the multiple-item processing view, which has important implications for current theories of visual search.

Remington, Roger W.; Horstmann, Gernot; Becker, Stefanie I.

2014-01-01

274

Searching for targets within the spatial layout of visual short-term memory.  

PubMed

Recent studies have revealed that the internal representations that we construct from the environment and maintain in visual short-term memory (VSTM) to guide behavior are highly flexible and can be selectively modulated according to our task goals and expectations. In the current study, we conducted two experiments to compare and contrast neural mechanisms of selective attention related to searching for target items within perceptual versus VSTM representations. We used event-related potentials to investigate whether searching for relevant target items from within VSTM representations involves spatially specific biasing of neural activity in a manner analogous to that which occurs during visual search for target items in perceptual arrays. The results, replicated across the two experiments, revealed that selection of a target object within a search array maintained in VSTM proceeds through a similar mechanism as that in the perceptual domain. In line with previous results, N2pc potentials were obtained when targets were identified within a perceptual visual-search array. Interestingly, equivalent N2pcs, with similar time courses and scalp distributions, were also elicited when target items were identified within a VSTM representation. The findings reinforce the notion of highly flexible VSTM representations that can be modulated according to task goals and suggest a large degree of overlap in the spatially specific neural mechanisms of target selection across the perceptual and VSTM domains. PMID:19553443

Kuo, Bo-Cheng; Rao, Anling; Lepsien, Jöran; Nobre, Anna Christina

2009-06-24

275

Pattern search algorithms for mixed variable general constrained optimization problems  

NASA Astrophysics Data System (ADS)

A new class of algorithms for solving nonlinearly constrained mixed variable optimization problems is presented. The Audet-Dennis Generalized Pattern Search (GPS) algorithm for bound constrained mixed variable optimization problems is extended to problems with general nonlinear constraints by incorporating a filter, in which new iterates are accepted whenever they decrease the incumbent objective function value or constraint violation function value. Additionally, the algorithm can exploit any available derivative information (or rough approximation thereof) to speed convergence without sacrificing the flexibility often employed by GPS methods to find better local optima. In generalizing existing GPS algorithms, the new theoretical convergence results presented here reduce seamlessly to existing results for more specific classes of problems. While no local continuity or smoothness assumptions are made, a hierarchy of theoretical convergence results is given, in which the assumptions dictate what can be proved about certain limit points of the algorithm. A new Matlab(c) software package was developed to implement these algorithms. Numerical results are provided for several nonlinear optimization problems from the CUTE test set, as well as a difficult nonlinearly constrained mixed variable optimization problem in the design of a load-bearing thermal insulation system used in cryogenic applications.

Abramson, Mark Aaron

276

Visual Recovery Patterns in Children with Leber's Hereditary Optic Neuropathy  

Microsoft Academic Search

Three patients with Leber’s hereditary optic neuropathy (LHON) showed spontaneous improvement in visual acuities after months\\u000a of legal blindness. Two male patients with bilateral subacute visual loss were 14 years of age at presentation. The first\\u000a male patient had a mitochondrial DNA mutation at nucleotide position 11778. The second male patient was found to be negative\\u000a for the designated primary

Gölge Acaro?lu; Tülay Kansu; Çi?dem F. Do?ulu

2001-01-01

277

The Importance of the Eye Area in Face Identification Abilities and Visual Search Strategies in Persons with Asperger Syndrome  

ERIC Educational Resources Information Center

Partly claimed to explain social difficulties observed in people with Asperger syndrome, face identification and visual search strategies become important. Previous research findings are, however, disparate. In order to explore face identification abilities and visual search strategies, with special focus on the importance of the eye area, 24…

Falkmer, Marita; Larsson, Matilda; Bjallmark, Anna; Falkmer, Torbjorn

2010-01-01

278

The processing of coherent global form and motion patterns without visual awareness  

PubMed Central

In the present study we addressed whether the processing of global form and motion was dependent on visual awareness. Continuous flash suppression (CFS) was used to suppress from awareness global dot motion (GDM) and Glass pattern stimuli. We quantified the minimum time taken for both pattern types to break suppression with the signal coherence of the pattern (0, 25, 50, and 100% signal) and the type of global structure (rotational, and radial) as independent variables. For both form and motion patterns increasing signal coherence decreased the time required to break suppression. This was the same for both rotational and radial global patterns. However, GDM patterns broke suppression faster than Glass patterns. In a supplementary experiment, we confirmed that this difference in break times is not because of the temporal nature of GDM patterns in attracting attention. In Experiment 2, we examined whether the processing of dynamic Glass patterns were similarly dependent on visual awareness. The processing of dynamic Glass patterns is involves both motion and form systems, and we questioned whether the interaction of these two systems was dependent on visual awareness. The suppression of dynamic Glass patterns was also dependent on signal coherence and the time course of suppression break resembled the detection of global motion and not global form. In Experiment 3 we ruled out the possibility that faster suppression break times was because the visual system is more sensitive to highly coherent form and motion patterns. Here contrast changing GDM and Glass patterns were superimposed on the dynamic CFS mask, and the minimum time required for them to be detected was measured. We showed that there was no difference in detection times for patterns of 0 and 100% coherence. The advantage of highly coherent global motion and form patterns in breaking suppression indicated that the processing and interaction of global motion and form systems occur without visual awareness.

Chung, Charles Y. L.; Khuu, Sieu K.

2014-01-01

279

Visualizing a High Recall Search Strategy Output for Undergraduates in an Exploration Stage of Researching a Term Paper.  

ERIC Educational Resources Information Center

Discusses high recall search strategies for undergraduates and how to overcome information overload that results. Highlights include word-based versus visual-based schemes; five summarization and visualization schemes for presenting information retrieval citation output; and results of a study that recommend visualization schemes geared toward…

Cole, Charles; Mandelblatt, Bertie; Stevenson, John

2002-01-01

280

The Mouse Model of Down Syndrome Ts65Dn Presents Visual Deficits as Assessed by Pattern Visual Evoked Potentials  

PubMed Central

Purpose. The Ts65Dn mouse is the most complete widely available animal model of Down syndrome (DS). Quantitative information was generated about visual function in the Ts65Dn mouse by investigating their visual capabilities by means of electroretinography (ERG) and patterned visual evoked potentials (pVEPs). Methods. pVEPs were recorded directly from specific regions of the binocular visual cortex of anesthetized mice in response to horizontal sinusoidal gratings of different spatial frequency, contrast, and luminance generated by a specialized video card and presented on a 21-in. computer display suitably linearized by gamma correction. Results. ERG assessments indicated no significant deficit in retinal physiology in Ts65Dn mice compared with euploid control mice. The Ts65Dn mice were found to exhibit deficits in luminance threshold, spatial resolution, and contrast threshold, compared with the euploid control mice. The behavioral counterparts of these parameters are luminance sensitivity, visual acuity, and the inverse of contrast sensitivity, respectively. Conclusions. DS includes various phenotypes associated with the visual system, including deficits in visual acuity, accommodation, and contrast sensitivity. The present study provides electrophysiological evidence of visual deficits in Ts65Dn mice that are similar to those reported in persons with DS. These findings strengthen the role of the Ts65Dn mouse as a model for DS. Also, given the historical assumption of integrity of the visual system in most behavioral assessments of Ts65Dn mice, such as the hidden-platform component of the Morris water maze, the visual deficits described herein may represent a significant confounding factor in the interpretation of results from such experiments.

Scott-McKean, Jonah Jacob; Chang, Bo; Hurd, Ronald E.; Nusinowitz, Steven; Schmidt, Cecilia; Davisson, Muriel T.

2010-01-01

281

Masked target transform volume clutter metric for human observer visual search modeling  

NASA Astrophysics Data System (ADS)

The Night Vision and Electronic Sensors Directorate (NVESD) develops an imaging system performance model to aid in the design and comparison of imaging systems for military use. It is intended to approximate visual task performance for a typical human observer with an imaging system of specified optical, electrical, physical, and environmental parameters. When modeling search performance, the model currently uses only target size and target-to-background contrast to describe a scene. The presence or absence of other non-target objects and textures in the scene also affect search performance, but NVESD's targeting task performance metric based time limited search model (TTP/TLS) does not currently account for them explicitly. Non-target objects in a scene that impact search performance are referred to as clutter. A universally accepted mathematical definition of clutter does not yet exist. Researchers have proposed a number of clutter metrics based on very different methods, but none account for display geometry or the varying spatial frequency sensitivity of the human visual system. After a review of the NVESD search model, properties of the human visual system, and a literature review of clutter metrics, the new masked target transform volume clutter metric will be presented. Next the results of an experiment designed to show performance variation due to clutter alone will be presented. Then, the results of three separate perception experiments using real or realistic search imagery will be used to show that the new clutter metric better models human observer search performance than the current NVESD model or any of the reviewed clutter metrics.

Moore, Richard Kirk

282

Saved by a log: how do humans perform hybrid visual and memory search?  

PubMed

Could you find 1 of your 1,000 Facebook friends in a crowd of 100? Even at a rate of 25 ms per comparison, determining that no friends were in the crowd would take more than 40 min if memory and visual search interacted linearly. In the experiment reported here, observers memorized pictures of 1 to 100 targets and then searched for any of these targets in visual displays of 1 to 16 objects. Response times varied linearly with visual set size but logarithmically with memory set size. Data from memory set sizes of 1 through 16 accurately predicted response times for different observers holding 100 objects in memory. The results would be consistent with a binary coding of visual objects in memory and are relevant to applied searches in which experts look for any of many items of interest (e.g., a radiologist running through a mental checklist of what might be wrong in a car-crash victim or an airport screener looking for any of a list of prohibited items in a carry-on bag). PMID:22623508

Wolfe, Jeremy M

2012-07-01

283

Global statistical regularities modulate the speed of visual search in patients with focal attentional deficits  

PubMed Central

There is growing evidence that the statistical properties of ensembles of similar objects are processed in a qualitatively different manner than the characteristics of individual items. It has recently been proposed that these types of perceptual statistical representations are part of a strategy to complement focused attention in order to circumvent the visual system’s limited capacity to represent more than a few individual objects in detail. Previous studies have demonstrated that patients with attentional deficits are nonetheless sensitive to these sorts of statistical representations. Here, we examined how such global representations may function to aid patients in overcoming focal attentional limitations by manipulating the statistical regularity of a visual scene while patients performed a search task. Three patients previously diagnosed with visual neglect searched for a target Gabor tilted to the left or right of vertical in displays of horizontal distractor Gabors. Although the local sizes of the distractors changed on every trial, the mean size remained stable for several trials. Patients made faster correct responses to targets in neglected regions of the visual field when global statistics remained constant over several trials, similar to age-matched controls. Given neglect patients’ attentional deficits, these results suggest that stable perceptual representations of global statistics can establish a context to speed search without the need to represent individual elements in detail.

Lanzoni, Lucilla; Melcher, David; Miceli, Gabriele; Corbett, Jennifer E.

2014-01-01

284

Verbal and visual reasoning in relation to patterns of Internet use  

Microsoft Academic Search

Purpose – The purpose of this paper is to examine cognitive differences between frequent and infrequent Internet users. Theoretically, culturally-valued use of the Internet is related to cognitive (i.e. intellectual) ability. Design\\/methodology\\/approach – A total of 406 college students completed measures of verbal reasoning, visual reasoning, and patterns of Internet use. Findings – Significant group differences in visual reasoning consistently

Genevieve Marie Johnson

2008-01-01

285

'Meaningful' patterns in visual noise: effects of lateral stimulation and the observer's belief in ESP.  

PubMed

Visual noise subjectively contains more meaningful patterns (1) when tachistoscopically presented to the left visual field, and (2) for persons who believe in extrasensory perception (ESP). These results indicate a possible right hemisphere mediation of delusional perception and suggest some delusional component in the belief in ESP. PMID:8190845

Brugger, P; Regard, M; Landis, T; Cook, N; Krebs, D; Niederberger, J

1993-01-01

286

The effect of caffeine ingestion on the perceived instability of visual patterns  

Microsoft Academic Search

The unique cytoarchitecture of the visual cortex, with cells of particular orientation-specificity arranged in vertical columns adjacent to other columns with somewhat different orientation-specificity causes subjective visual instabilities when viewing some repetitive grid patterns for normal subjects. Since caffeine increases cortical arousal by serving as an antagonist to the inhibitory neurotransmitter adenosine, caffeine intake might be expected to increase these

Stanley Coren

2002-01-01

287

Visual Intelligence: Using the Deep Patterns of Visual Language to Build Cognitive Skills  

ERIC Educational Resources Information Center

Thirty years of work as a graphic facilitator listening visually to people in every kind of organization has convinced the author that visual intelligence is a key to navigating an information economy rich with multimedia. He also believes that theory and disciplines developed by practitioners in this new field hold special promise for educators…

Sibbet, David

2008-01-01

288

Visual Ability and Searching Behavior of Adult Laricobius nigrinus, a Hemlock Woolly Adelgid Predator  

PubMed Central

Very little is known about the searching behavior and sensory cues that Laricobius spp. (Coleoptera: Derodontidae) predators use to locate suitable habitats and prey, which limits our ability to collect and monitor them for classical biological control of adelgids (Hemiptera: Adelgidae). The aim of this study was to examine the visual ability and the searching behavior of newly emerged L. nigrinus Fender, a host-specific predator of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Phylloxeroidea: Adelgidae). In a laboratory bioassay, individual adults attempting to locate an uninfested eastern hemlock seedling under either light or dark conditions were observed in an arena. In another bioassay, individual adults searching for prey on hemlock seedlings (infested or uninfested) were continuously video-recorded. Beetles located and began climbing the seedling stem in light significantly more than in dark, indicating that vision is an important sensory modality. Our primary finding was that searching behavior of L. nigrinus, as in most species, was related to food abundance. Beetles did not fly in the presence of high A. tsugae densities and flew when A. tsugae was absent, which agrees with observed aggregations of beetles on heavily infested trees in the field. At close range of prey, slow crawling and frequent turning suggest the use of non-visual cues such as olfaction and contact chemoreception. Based on the beetles' visual ability to locate tree stems and their climbing behavior, a bole trap may be an effective collection and monitoring tool.

Mausel, D.L.; Salom, S.M.; Kok, L.T.

2011-01-01

289

Electromagnetic energy absorption patterns in subjects with common visual disorders.  

PubMed

This article describes the analysis of electromagnetic energy absorption properties of models of the human eye with common visual disorders. The investigation addresses two types of visual disorders, namely hyperopia (or farsightedness) and myopia (or nearsightedness). Calculations were carried out using plane multilayered method with common wireless communication frequencies of 900, 1800, and 2450 MHz. The effect of wireless radiation on the eye is studied by calculation of the specific absorption rate (SAR) in three different eye models. The results of the simulations confirmed the anticipated and more complex relationship between absorption and structural variations of the eye at these frequencies. PMID:21861692

Gasmelseed, Akram

2011-09-01

290

Effect of pattern complexity on the visual span for Chinese and alphabet characters  

PubMed Central

The visual span for reading is the number of letters that can be recognized without moving the eyes and is hypothesized to impose a sensory limitation on reading speed. Factors affecting the size of the visual span have been studied using alphabet letters. There may be common constraints applying to recognition of other scripts. The aim of this study was to extend the concept of the visual span to Chinese characters and to examine the effect of the greater complexity of these characters. We measured visual spans for Chinese characters and alphabet letters in the central vision of bilingual subjects. Perimetric complexity was used as a metric to quantify the pattern complexity of binary character images. The visual span tests were conducted with four sets of stimuli differing in complexity—lowercase alphabet letters and three groups of Chinese characters. We found that the size of visual spans decreased with increasing complexity, ranging from 10.5 characters for alphabet letters to 4.5 characters for the most complex Chinese characters studied. A decomposition analysis revealed that crowding was the dominant factor limiting the size of the visual span, and the amount of crowding increased with complexity. Errors in the spatial arrangement of characters (mislocations) had a secondary effect. We conclude that pattern complexity has a major effect on the size of the visual span, mediated in large part by crowding. Measuring the visual span for Chinese characters is likely to have high relevance to understanding visual constraints on Chinese reading performance.

Wang, Hui; He, Xuanzi; Legge, Gordon E.

2014-01-01

291

Effect of pattern complexity on the visual span for Chinese and alphabet characters.  

PubMed

THE VISUAL SPAN FOR READING IS THE NUMBER OF LETTERS THAT CAN BE RECOGNIZED WITHOUT MOVING THE EYES AND IS HYPOTHESIZED TO IMPOSE A SENSORY LIMITATION ON READING SPEED FACTORS AFFECTING THE SIZE OF THE VISUAL SPAN HAVE BEEN STUDIED USING ALPHABET LETTERS THERE MAY BE COMMON CONSTRAINTS APPLYING TO RECOGNITION OF OTHER SCRIPTS THE AIM OF THIS STUDY WAS TO EXTEND THE CONCEPT OF THE VISUAL SPAN TO CHINESE CHARACTERS AND TO EXAMINE THE EFFECT OF THE GREATER COMPLEXITY OF THESE CHARACTERS WE MEASURED VISUAL SPANS FOR CHINESE CHARACTERS AND ALPHABET LETTERS IN THE CENTRAL VISION OF BILINGUAL SUBJECTS PERIMETRIC COMPLEXITY WAS USED AS A METRIC TO QUANTIFY THE PATTERN COMPLEXITY OF BINARY CHARACTER IMAGES THE VISUAL SPAN TESTS WERE CONDUCTED WITH FOUR SETS OF STIMULI DIFFERING IN COMPLEXITYLOWERCASE ALPHABET LETTERS AND THREE GROUPS OF CHINESE CHARACTERS WE FOUND THAT THE SIZE OF VISUAL SPANS DECREASED WITH INCREASING COMPLEXITY, RANGING FROM 105 CHARACTERS FOR ALPHABET LETTERS TO 45 CHARACTERS FOR THE MOST COMPLEX CHINESE CHARACTERS STUDIED A DECOMPOSITION ANALYSIS REVEALED THAT CROWDING WAS THE DOMINANT FACTOR LIMITING THE SIZE OF THE VISUAL SPAN, AND THE AMOUNT OF CROWDING INCREASED WITH COMPLEXITY ERRORS IN THE SPATIAL ARRANGEMENT OF CHARACTERS MISLOCATIONS HAD A SECONDARY EFFECT WE CONCLUDE THAT PATTERN COMPLEXITY HAS A MAJOR EFFECT ON THE SIZE OF THE VISUAL SPAN, MEDIATED IN LARGE PART BY CROWDING MEASURING THE VISUAL SPAN FOR CHINESE CHARACTERS IS LIKELY TO HAVE HIGH RELEVANCE TO UNDERSTANDING VISUAL CONSTRAINTS ON CHINESE READING PERFORMANCE: PMID:24993020

Wang, Hui; He, Xuanzi; Legge, Gordon E

2014-01-01

292

Visualizing patterns in a global terrorism incident database  

Microsoft Academic Search

The terrorism database includes more than 27 000 terrorism incidents between 1968 and 2006. Each incident record has spatial information (country names for all records and city names for some records), a time stamp (ie year, month, and day), and several other fields (eg tactics, weapon types, target types, fatalities, and injuries). We introduce a unified visualization environment that is able

Diansheng Guo; Ke Liao; Michael Morgan

2007-01-01

293

Visual Search with Image Modification in Age-Related Macular Degeneration  

PubMed Central

Purpose. AMD results in loss of central vision and a dependence on low-resolution peripheral vision. While many image enhancement techniques have been proposed, there is a lack of quantitative comparison of the effectiveness of enhancement. We developed a natural visual search task that uses patients' eye movements as a quantitative and functional measure of the efficacy of image modification. Methods. Eye movements of 17 patients (mean age = 77 years) with AMD were recorded while they searched for target objects in natural images. Eight different image modification methods were implemented and included manipulations of local image or edge contrast, color, and crowding. In a subsequent task, patients ranked their preference of the image modifications. Results. Within individual participants, there was no significant difference in search duration or accuracy across eight different image manipulations. When data were collapsed across all image modifications, a multivariate model identified six significant predictors for normalized search duration including scotoma size and acuity, as well as interactions among scotoma size, age, acuity, and contrast (P < 0.05). Additionally, an analysis of image statistics showed no correlation with search performance across all image modifications. Rank ordering of enhancement methods based on participants' preference revealed a trend that participants preferred the least modified images (P < 0.05). Conclusions. There was no quantitative effect of image modification on search performance. A better understanding of low- and high-level components of visual search in natural scenes is necessary to improve future attempts at image enhancement for low vision patients. Different search tasks may require alternative image modifications to improve patient functioning and performance.

Wiecek, Emily; Jackson, Mary Lou; Dakin, Steven C.; Bex, Peter

2012-01-01

294

Solution of Different Types of Economic Load Dispatch Problems Using a Pattern Search Method  

Microsoft Academic Search

Direct search (DS) methods are evolutionary algorithms used to solve constrained optimization problems. DS methods do not require information about the gradient of the objective function when searching for an optimum solution. One such method is a pattern search (PS) algorithm. This study presents a new approach based on a constrained PS algorithm to solve various types of power system

J. S. Al-Sumait; J. K. Sykulski; A. K. Al-Othman

2008-01-01

295

Patterns of visual attention to faces and objects in autism spectrum disorder  

PubMed Central

This study used eye-tracking to examine visual attention to faces and objects in adolescents with autism spectrum disorder (ASD) and typical peers. Point of gaze was recorded during passive viewing of images of human faces, inverted human faces, monkey faces, three-dimensional curvilinear objects, and two-dimensional geometric patterns. Individuals with ASD obtained lower scores on measures of face recognition and social-emotional functioning but exhibited similar patterns of visual attention. In individuals with ASD, face recognition performance was associated with social adaptive function. Results highlight heterogeneity in manifestation of social deficits in ASD and suggest that naturalistic assessments are important for quantifying atypicalities in visual attention.

McPartland, James C.; Webb, Sara Jane; Keehn, Brandon; Dawson, Geraldine

2011-01-01

296

Visual experience-dependent maturation of correlated neuronal activity patterns in a developing visual system  

PubMed Central

The functional properties of neural circuits become increasingly robust over development. This allows circuits to optimize their output in response to a variety of input. However it is not clear whether this optimization is a function of hardwired circuit elements, or whether it requires neural experience in order to develop. Here we perform rapid in vivo imaging of calcium signals from bulk-labeled neurons in the Xenopus laevis optic tectum in order to resolve the rapid spatiotemporal response properties of populations of developing tectal neurons in response to visual stimuli. We find that during a critical time in tectal development, network activity becomes increasingly robust, more correlated and more synchronous. These developmental changes require normal visual input during development and are disrupted by NMDA receptor blockade. Our data show that visual activity and NMDAR activation are critical for the maturation of tectal network dynamics during visual system development.

Xu, Heng; Khakhalin, Arseny S.; Nurmikko, Arto V.; Aizenman, Carlos D.

2011-01-01

297

On the selection and evaluation of visual display symbology Factors influencing search and identification times  

NASA Technical Reports Server (NTRS)

Three single-target visual search tasks were used to evaluate a set of cathode-ray tube (CRT) symbols for a helicopter situation display. The search tasks were representative of the information extraction required in practice, and reaction time was used to measure the efficiency with which symbols could be located and identified. Familiar numeric symbols were responded to more quickly than graphic symbols. The addition of modifier symbols, such as a nearby flashing dot or surrounding square, had a greater disruptive effect on the graphic symbols than did the numeric characters. The results suggest that a symbol set is, in some respects, like a list that must be learned. Factors that affect the time to identify items in a memory task, such as familiarity and visual discriminability, also affect the time to identify symbols. This analogy has broad implications for the design of symbol sets. An attempt was made to model information access with this class of display.

Remington, Roger; Williams, Douglas

1986-01-01

298

The evaluation of display symbology - A chronometric study of visual search. [on cathode ray tubes  

NASA Technical Reports Server (NTRS)

Three single-target visual search tasks were used to evaluate a set of CRT symbols for a helicopter traffic display. The search tasks were representative of the kinds of information extraction required in practice, and reaction time was used to measure the efficiency with which symbols could be located and identified. The results show that familiar numeric symbols were responded to more quickly than graphic symbols. The addition of modifier symbols such as a nearby flashing dot or surrounding square had a greater disruptive effect on the graphic symbols than the alphanumeric characters. The results suggest that a symbol set is like a list that must be learned. Factors that affect the time to respond to items in a list, such as familiarity and visual discriminability, and the division of list items into categories, also affect the time to identify symbols.

Remington, R.; Williams, D.

1984-01-01

299

Human Visual Search Does Not Maximize the Post-Saccadic Probability of Identifying Targets  

PubMed Central

Researchers have conjectured that eye movements during visual search are selected to minimize the number of saccades. The optimal Bayesian eye movement strategy minimizing saccades does not simply direct the eye to whichever location is judged most likely to contain the target but makes use of the entire retina as an information gathering device during each fixation. Here we show that human observers do not minimize the expected number of saccades in planning saccades in a simple visual search task composed of three tokens. In this task, the optimal eye movement strategy varied, depending on the spacing between tokens (in the first experiment) or the size of tokens (in the second experiment), and changed abruptly once the separation or size surpassed a critical value. None of our observers changed strategy as a function of separation or size. Human performance fell far short of ideal, both qualitatively and quantitatively.

Morvan, Camille; Maloney, Laurence T.

2012-01-01

300

Using facial emotional stimuli in visual search experiments: The arousal factor explains contradictory results.  

PubMed

For more than two decades, visual search experiments using pictures of emotional faces as stimuli have generated contradictory results. Evidence of a superior detection of angry faces compared to happy faces have been mixed with an equal amount of evidence in the opposite direction. In this article, we review this literature, and examine the hypothesis that the neglected stimulus factor of emotional arousal may explain these contradictory results. Through an extensive reanalysis of results from our own laboratory as well as from other researchers, we show that the arousal factor systematically influences the outcome of the reviewed visual search experiments, and may thus provide a key to the historical contradictions within this research field. PMID:24341823

Lundqvist, Daniel; Juth, Pernilla; Ohman, Arne

2014-09-01

301

Learning from data: recognizing glaucomatous defect patterns and detecting progression from visual field measurements.  

PubMed

A hierarchical approach to learn from visual field data was adopted to identify glaucomatous visual field defect patterns and to detect glaucomatous progression. The analysis pipeline included three stages, namely, clustering, glaucoma boundary limit detection, and glaucoma progression detection testing. First, cross-sectional visual field tests collected from each subject were clustered using a mixture of Gaussians and model parameters were estimated using expectation maximization. The visual field clusters were further estimated to recognize glaucomatous visual field defect patterns by decomposing each cluster into several axes. The glaucoma visual field defect patterns along each axis then were identified. To derive a definition of progression, the longitudinal visual fields of stable glaucoma eyes on the abnormal cluster axes were projected and the slope was approximated using linear regression (LR) to determine the confidence limit of each axis. For glaucoma progression detection, the longitudinal visual fields of each eye on the abnormal cluster axes were projected and the slope was approximated by LR. Progression was assigned if the progression rate was greater than the boundary limit of the stable eyes; otherwise, stability was assumed. The proposed method was compared to a recently developed progression detection method and to clinically available glaucoma progression detection software. The clinical accuracy of the proposed pipeline was as good as or better than the currently available methods. PMID:24710816

Yousefi, Siamak; Goldbaum, Michael H; Balasubramanian, Madhusudhanan; Medeiros, Felipe A; Zangwill, Linda M; Liebmann, Jeffrey M; Girkin, Christopher A; Weinreb, Robert N; Bowd, Christopher

2014-07-01

302

Searching for Complex Patterns Using Disjunctive Anomaly Detection  

PubMed Central

Objective Disjunctive anomaly detection (DAD) algorithm [1] can efficiently search across multidimensional biosurveillance data to find multiple simultaneously occurring (in time) and overlapping (across different data dimensions) anomalous clusters. We introduce extensions of DAD to handle rich cluster interactions and diverse data distributions. Introduction Modern biosurveillance data contains thousands of unique time series defined across various categorical dimensions (zipcode, age groups, hospitals). Many algorithms are overly specific (tracking each time series independently would often miss early signs of outbreaks), or too general (detections at state level may lack specificity reflective of the actual process at hand). Disease outbreaks often impact multiple values (disjunctive sets of zipcodes, hospitals, multiple age groups) along subsets of multiple dimensions of data. It is not uncommon to see outbreaks of different diseases occurring simultaneously (e.g. food poisoning and flu) making it hard to detect and characterize the individual events. We proposed Disjunctive Anomaly Detection (DAD) algorithm [1] to efficiently search across millions of potential clusters defined as conjunctions over dimensions and disjunctions over values along each dimension. An example anomalous cluster detectable by DAD may identify zipcode = {z1 or z2 or z3 or z5} and age_group = {child or senior} to show unusual activity in the aggregate. Such conjunctive-disjunctive language of cluster definitions enables finding real-world outbreaks that are often missed by other state-of-art algorithms like What’s Strange About Recent Events (WSARE) [3] or Large Average Submatrix (LAS) [2]. DAD is able to identify multiple interesting clusters simultaneously and better explain complex anomalies in data than those alternatives. Methods We define the observed counts of patients reporting on a given day as a random variable for each unique combination of values along all dimensions. DAD iteratively identifies K subsets of these variables along with corresponding ranges of their values and time intervals that show increased activity that cannot be explained by random fluctuations (K is generally unknown and could be 0). The resulting set of clusters maximizes data likelihood while controlling for overall complexity. We have successfully derived a versatile set of scoring functions that allow Normal, Poisson, Exponential or Non-parametric assumptions about the underlying data distributions, and accommodate additive-scaled, additive-unscaled or multiplicative-scaled models for the clusters. Results We present results of testing DAD on two real-world datasets. One of them contains daily outpatient visit counts from 26 regions in Sri Lanka involving 9 common diseases. The other data contains semi-synthetically generated terrorist activities throughout regions of Afghanistan (Sigacts). Both span multiple years and are representative of data seen in biosurveillance applications. Figure 1 shows DAD systematically outperforming WSARE and LAS. Each algorithm’s parameters were tuned to generate one false positive per month in baseline data. The graphs represent average days-to-detect performance of 100 sets with synthetically injected clusters using additive-scaled (AS), additive-unscaled (AU), and multiplicative-scaled (MS) models of cluster interactions. Conclusions We extend applicability of DAD algorithm to handle wide variety of input data distributions and various outbreak models. DAD efficiently scans over millions of potential outbreak patterns and accurately and timely reports complex outbreak interactions with speed that meets requirements of practical applications.

Sabhnani, Maheshkumar; Dubrawski, Artur; Schneider, Jeff

2013-01-01

303

Visual cluster analysis and pattern recognition template and methods  

DOEpatents

A method of clustering using a novel template to define a region of influence is disclosed. Using neighboring approximation methods, computation times can be significantly reduced. The template and method are applicable and improve pattern recognition techniques. 30 figs.

Osbourn, G.C.; Martinez, R.F.

1999-05-04

304

Visual cluster analysis and pattern recognition template and methods  

DOEpatents

A method of clustering using a novel template to define a region of influence. Using neighboring approximation methods, computation times can be significantly reduced. The template and method are applicable and improve pattern recognition techniques.

Osbourn, Gordon Cecil (Albuquerque, NM); Martinez, Rubel Francisco (Albuquerque, NM)

1999-01-01

305

Epistemic Beliefs, Online Search Strategies, and Behavioral Patterns While Exploring Socioscientific Issues  

NASA Astrophysics Data System (ADS)

Online information searching tasks are usually implemented in a technology-enhanced science curriculum or merged in an inquiry-based science curriculum. The purpose of this study was to examine the role students' different levels of scientific epistemic beliefs (SEBs) play in their online information searching strategies and behaviors. Based on the measurement of an SEB survey, 42 undergraduate and graduate students in Taiwan were recruited from a pool of 240 students and were divided into sophisticated and naïve SEB groups. The students' self-perceived online searching strategies were evaluated by the Online Information Searching Strategies Inventory, and their search behaviors were recorded by screen-capture videos. A sequential analysis was further used to analyze the students' searching behavioral patterns. The results showed that those students with more sophisticated SEBs tended to employ more advanced online searching strategies and to demonstrate a more metacognitive searching pattern.

Hsu, Chung-Yuan; Tsai, Meng-Jung; Hou, Huei-Tse; Tsai, Chin-Chung

2014-06-01

306

Revisiting Web Design Guidelines by Exploring Users’ Expectations, Preferences and Visual Search Behaviour  

Microsoft Academic Search

The majority of existing Web design guidelines have been derived by expert heuristic evaluations, apparently without involving\\u000a the users themselves. In this paper we report two studies of an on-going research programme in the area of eye tracking in\\u000a which we are investigating the relationship between the users’ expectations, preferences, and visual search behaviour. The\\u000a first study captures the position

Ekaterini Tzanidou; Shailey Minocha; Marian Petre; Andrew Grayson

307

Hypothesis Support Mechanism for Mid-Level Visual Pattern Recognition  

NASA Technical Reports Server (NTRS)

A method of mid-level pattern recognition provides for a pose invariant Hough Transform by parametrizing pairs of points in a pattern with respect to at least two reference points, thereby providing a parameter table that is scale- or rotation-invariant. A corresponding inverse transform may be applied to test hypothesized matches in an image and a distance transform utilized to quantify the level of match.

Amador, Jose J (Inventor)

2007-01-01

308

Executive working memory load does not compromise perceptual processing during visual search: evidence from additive factors analysis.  

PubMed

Executive working memory (WM) load reduces the efficiency of visual search, but the mechanisms by which this occurs are not fully known. In the present study, we assessed the effect of executive load on perceptual processing during search. Participants performed a serial oculomotor search task, looking for a circle target among gapped-circle distractors. The participants performed the task under high and low executive WM load, and the visual quality (Experiment 1) or discriminability of targets and distractors (Experiment 2) was manipulated across trials. By the logic of the additive factors method (Sternberg, 1969, 1998), if WM load compromises the quality of perceptual processing during visual search, manipulations of WM load and perceptual processing difficulty should produce nonadditive effects. Contrary to this prediction, the effects of WM load and perceptual difficulty were additive. The results imply that executive WM load does not degrade perceptual analysis during visual search. PMID:20139447

He, Jibo; McCarley, Jason S

2010-02-01

309

Time Course of Motor Preparation during Visual Search with Flexible Stimulus-Response Association  

PubMed Central

Whether allocation of visuospatial attention can be divorced from saccade preparation has been the subject of intense research efforts. A variant of the visual search paradigm, in which a feature singleton indicates that the correct saccade should be directed to it (prosaccade) or to the opposite distractor (antisaccade), has been influential in addressing this core topic. We performed a causal assessment of this controversy by delivering an air puff to one eye to invoke the trigeminal blink reflex as monkeys performed this visual search task. Blinks effectively remove saccadic inhibition and prematurely trigger impending saccades in reaction time tasks, thus providing a behavioral readout of the premotor plan. We found that saccades accompanied blinks during the initial allocation of attention epoch and that these movements were directed to the singleton for both prosaccade and antisaccade trials. Blinks evoked at later times were accompanied with saccades to the correct end point location: the singleton on prosaccade trials and the opposite distractor on antisaccade trials. These results provide support for concurrent encoding of visuospatial attention and saccade preparation during visual search behavior.

Katnani, Husam A.

2013-01-01

310

Modeling the effect of selection history on pop-out visual search.  

PubMed

While attentional effects in visual selection tasks have traditionally been assigned "top-down" or "bottom-up" origins, more recently it has been proposed that there are three major factors affecting visual selection: (1) physical salience, (2) current goals and (3) selection history. Here, we look further into selection history by investigating Priming of Pop-out (POP) and the Distractor Preview Effect (DPE), two inter-trial effects that demonstrate the influence of recent history on visual search performance. Using the Ratcliff diffusion model, we model observed saccadic selections from an oddball search experiment that included a mix of both POP and DPE conditions. We find that the Ratcliff diffusion model can effectively model the manner in which selection history affects current attentional control in visual inter-trial effects. The model evidence shows that bias regarding the current trial's most likely target color is the most critical parameter underlying the effect of selection history. Our results are consistent with the view that the 3-item color-oddball task used for POP and DPE experiments is best understood as an attentional decision making task. PMID:24595032

Tseng, Yuan-Chi; Glaser, Joshua I; Caddigan, Eamon; Lleras, Alejandro

2014-01-01

311

Production and perception rules underlying visual patterns: effects of symmetry and hierarchy  

PubMed Central

Formal language theory has been extended to two-dimensional patterns, but little is known about two-dimensional pattern perception. We first examined spontaneous two-dimensional visual pattern production by humans, gathered using a novel touch screen approach. Both spontaneous creative production and subsequent aesthetic ratings show that humans prefer ordered, symmetrical patterns over random patterns. We then further explored pattern-parsing abilities in different human groups, and compared them with pigeons. We generated visual plane patterns based on rules varying in complexity. All human groups tested, including children and individuals diagnosed with autism spectrum disorder (ASD), were able to detect violations of all production rules tested. Our ASD participants detected pattern violations with the same speed and accuracy as matched controls. Children's ability to detect violations of a relatively complex rotational rule correlated with age, whereas their ability to detect violations of a simple translational rule did not. By contrast, even with extensive training, pigeons were unable to detect orientation-based structural violations, suggesting that, unlike humans, they did not learn the underlying structural rules. Visual two-dimensional patterns offer a promising new formally-grounded way to investigate pattern production and perception in general, widely applicable across species and age groups.

Westphal-Fitch, Gesche; Huber, Ludwig; Gomez, Juan Carlos; Fitch, W. Tecumseh

2012-01-01

312

Visualization of gunshot residue patterns on dark clothing.  

PubMed

Determination of the muzzle-to-target distance is often a critical factor in criminal and civil investigations involving firearms. However, seeing and recording gunshot residue patterns can be difficult if the victim's clothing is dark and/or bloodstained. Trostle reported the use of infrared film for the detection of burn patterns. However, only after the film is developed are the results visible and multiple exposures at different settings may be needed. The Video Spectral Comparator 2000 (Foster & Freeman Ltd., Evesham, Worcestershire, U.K.) is an imaging instrument routinely used by forensic document examiners. Without use of specialized film could the VSC 2000 (at appropriate instrument settings) quickly, easily, and reliably provide instantaneous viewing, saving, and printing of gunshot residue patterns on dark and/or blood soaked clothing? At muzzle-to-target distances of 6, 12, and 18 in., test fires were made into five different types of dark clothing using eight different handguns of different calibers. Gunshot residues were detected for all eight calibers, and powder burn patterns were seen on dark clothing for all three target distances and calibers except 0.22 long rifle and 0.25 ACP. Bloodstains did not preclude the viewing of these patterns. PMID:17018087

Atwater, Christina S; Durina, Marie E; Durina, John P; Blackledge, Robert D

2006-09-01

313

Age differences in visual search for traffic signs during a simulated conversation.  

PubMed

The effects of divided attention were examined in younger adults (M = 23 years) and older adults (M = 64 years) who searched for traffic signs in digitized images of traffic scenes. Sign search was executed under single-task and dual-task conditions in scenes containing either small or large amounts of visual clutter. For both age groups, clutter and the secondary task had additive effects on search accuracy, speed, and oculomotor involvement. Compared with the younger adults, older adults were less accurate, especially with high-clutter scenes, were slower to decide that a target sign was not present, and exhibited a marginally greater divided-attention effect on reaction times. They exhibited longer fixations in the divided-attention condition, in which they also showed a disproportionate reduction in recognition memory for the content of the secondary task. Actual or potential applications of this research include methods for evaluating the distraction of conversations and safety implications of conversation on visual search behavior. PMID:15709329

McPhee, Lisa C; Scialfa, Charles T; Dennis, Wanda M; Ho, Geoffrey; Caird, Jeff K

2004-01-01

314

Visual search and attention in blue jays (Cyanocitta cristata): Associative cuing and sequential priming.  

PubMed

Visual search for complex natural targets requires focal attention, either cued by predictive stimulus associations or primed by a representation of the most recently detected target. Because both processes can focus visual attention, cuing and priming were compared in an operant search task to evaluate their relative impacts on performance and to determine the nature of their interaction in combined treatments. Blue jays were trained to search for pairs of alternative targets among distractors. Informative or ambiguous color cues were provided before each trial, and targets were presented either in homogeneous blocked sequences or in constrained random order. Initial task acquisition was facilitated by priming in general, but was significantly retarded when targets were both cued and primed, indicating that the two processes interfered with each other during training. At asymptote, attentional effects were manifested mainly in inhibition, increasing latency in miscued trials and decreasing accuracy on primed trials following an unexpected target switch. A combination of cuing and priming was found to interfere with performance in such unexpected trials, apparently a result of the limited capacity of working memory. Because the ecological factors that promote priming or cuing are rather disparate, it is not clear whether they ever simultaneously contribute to natural predatory search. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:24893217

Goto, Kazuhiro; Bond, Alan B; Burks, Marianna; Kamil, Alan C

2014-04-01

315

White matter hyperintensities are associated with visual search behavior independent of generalized slowing in aging.  

PubMed

A fundamental controversy is whether cognitive decline with advancing age can be entirely explained by decreased processing speed, or whether specific neural changes can elicit cognitive decline, independent of slowing. These hypotheses are anchored by studies of healthy older individuals where age is presumed the sole influence. Unfortunately, advancing age is also associated with asymptomatic brain white matter injury. We hypothesized that differences in white matter injury extent, manifest by MRI white matter hyperintensities (WMH), mediate differences in visual attentional control in healthy aging, beyond processing speed differences. We tested young and cognitively healthy older adults on search tasks indexing speed and attentional control. Increasing age was associated with generally slowed performance. WMH were also associated with slowed search times independent of processing speed differences. Consistent with evidence attributing reduced network connectivity to WMH, these results conclusively demonstrate that clinically silent white matter injury contributes to slower search performance indicative of compromised cognitive control, independent of generalized slowing of processing speed. PMID:24183716

Lockhart, Samuel N; Roach, Alexandra E; Luck, Steven J; Geng, Joy; Beckett, Laurel; Carmichael, Owen; DeCarli, Charles

2014-01-01

316

Visual search for traffic signs: the effects of clutter, luminance, and aging.  

PubMed

Latency and eye movement measures were used to examine the effects of aging, clutter, and luminance on visual search for traffic signs embedded in digitized images of driving scenes. Initially 14 older and 14 younger observers classified daytime and nighttime traffic scenes as containing low or high amounts of clutter. Next, an independent sample of 14 younger and 14 older participants searched for traffic signs contained within these scenes. Errors were more common among the elderly. Search efficiency declined with increased clutter and with aging. However, relative to the young, older adults did not suffer disproportionately as a result of increased clutter. The methods developed might be profitably employed to assess sign conspicuity and sign acquisition during driving. PMID:11592661

Ho, G; Scialfa, C T; Caird, J K; Graw, T

2001-01-01

317

Using computer animation to visualize space - time patterns  

Microsoft Academic Search

The geographic information revolution is rapidly increasing the availability of data that are referenced both by space and by time coordinates. This creates new opportunities for analysis, but also causes enormous problems as analytical tools able to depict, detect, or measure patterns in space - time data are poorly developed. The question arises as to whether or not a greater

D Dorling; S Openshaw

1992-01-01

318

PATTERN REVERSAL VISUAL EVOKED POTENTIALS IN AWAKE RATS  

EPA Science Inventory

A method for recording pattern reversal evoked potentials (PREPs) from awake restrained rats has been developed. The procedure of Onofrj et al. was modified to eliminate the need for anesthetic, thereby avoiding possible interactions of the anesthetic with other manipulations of ...

319

The NLP Swish Pattern: An Innovative Visualizing Technique.  

ERIC Educational Resources Information Center

Describes swish pattern, one of many innovative therapeutic interventions that developers of neurolinguistic programing (NLP) have contributed to counseling profession. Presents brief overview of NLP followed by an explanation of the basic theory and expected outcomes of the swish. Presents description of the intervention process and case studies…

Masters, Betsy J.; And Others

1991-01-01

320

Visualization of Flow Pattern in Thermosyphon by ECT  

NASA Astrophysics Data System (ADS)

An investigation on the visualization of the flow of the liquid in a two-phase closed thermosyphon (TPCT) is carried out. Electrical capacitance tomography (ECT) with optimal step lengths for iterative image reconstruction algorithm is applied in the study. Measurements are made under a range of heating rates of the TPCT. As against the common assumption of ``low spatial resolution of ECT'', the experimental results have demonstrated ECT's capability of reconstructing images of thin films on the order of 100 ?m in thickness. Results for film thickness by ECT are compared with the established theory. Agreements and discrepancies are observed among the reconstructed images corresponding to difference thresholds. ECT images of the liquid distributions in the TPCT show clear dependence on the variation of working conditions, which proves the potential of ECT as an advantageous technique for monitoring the operation of TPCT.

Liu, Shi; Li, Jingtao; Chen, Qi

2007-06-01

321

Effects of identical context on visual pattern recognition by pigeons  

Microsoft Academic Search

The effects of identical context on pattern recognition by pigeons for outline drawings of faces were investigated by training\\u000a pigeons to identify (Experiment 1) and categorize (Experiment 2) these stimuli according to the orientation of the mouth—an\\u000a upright U shape representing a smiling mouth or an inverted U shape representing a sad mouth. These target stimuli were presented\\u000a alone (Pair

Francisco J. Donis; Sheila Chase; Eric G. Heinemann

2005-01-01

322

Neural Correlates of Changes in a Visual Search Task due to Cognitive Training in Seniors  

PubMed Central

This study aimed to elucidate the underlying neural sources of near transfer after a multidomain cognitive training in older participants in a visual search task. Participants were randomly assigned to a social control, a no-contact control and a training group, receiving a 4-month paper-pencil and PC-based trainer guided cognitive intervention. All participants were tested in a before and after session with a conjunction visual search task. Performance and event-related potentials (ERPs) suggest that the cognitive training improved feature processing of the stimuli which was expressed in an increased rate of target detection compared to the control groups. This was paralleled by enhanced amplitudes of the frontal P2 in the ERP and by higher activation in lingual and parahippocampal brain areas which are discussed to support visual feature processing. Enhanced N1 and N2 potentials in the ERP for nontarget stimuli after cognitive training additionally suggest improved attention and subsequent processing of arrays which were not immediately recognized as targets. Possible test repetition effects were confined to processes of stimulus categorisation as suggested by the P3b potential. The results show neurocognitive plasticity in aging after a broad cognitive training and allow pinpointing the functional loci of effects induced by cognitive training.

Wild-Wall, Nele; Falkenstein, Michael; Gajewski, Patrick D.

2012-01-01

323

OCLC Search Key Usage Patterns in a Large Research Library.  

ERIC Educational Resources Information Center

Reports the results of a study performed to determine preferred and effective usage of search keys utilized by OCLC users. The study used the research library facilities of Ohio State University to examine information retrieval behavior for acquisitions and cataloging information. (RAA)

Rastogi, Kunj B.; Morita, Ichiko T.

1981-01-01

324

Designing photometric patterns for exoplanet transit search on board COROT  

Microsoft Academic Search

COROT is a mission of the CNES space agency, to be launched in 2005 in a near Polar orbit. It is devoted to star seismology and to exoplanetary transit search. Five star fields chosen close to the galactic plane will be observed during the mission with a high photometric accuracy (relative). Each observation run will last 150 days monitoring continuously

Antoine Llebaria; Andre Vuillemin; P. Guterman; Pierre Barge

2002-01-01

325

Effects of interior bezels of tiled-monitor large displays on visual search, tunnel steering, and target selection  

Microsoft Academic Search

Tiled-monitor large displays are widely used in various application domains. However, how their interior bezels affect user performance and behavior has not been fully understood. We conducted three controlled experiments to investigate effects of tiled-monitor interior bezels on visual search, straight-tunnel steering, and target selection tasks. The conclusions of our paper are: 1) interior bezels do not affect visual search

Xiaojun Bi; Seok-Hyung Bae; Ravin Balakrishnan

2010-01-01

326

Use of a twin dataset to identify AMD-related visual patterns controlled by genetic factors  

NASA Astrophysics Data System (ADS)

The mapping of genotype to the phenotype of age-related macular degeneration (AMD) is expected to improve the diagnosis and treatment of the disease in a near future. In this study, we focused on the first step to discover this mapping: we identified visual patterns related to AMD which seem to be controlled by genetic factors, without explicitly relating them to the genes. For this purpose, we used a dataset of eye fundus photographs from 74 twin pairs, either monozygotic twins, who have the same genotype, or dizygotic twins, whose genes responsible for AMD are less likely to be identical. If we are able to differentiate monozygotic twins from dizygotic twins, based on a given visual pattern, then this pattern is likely to be controlled by genetic factors. The main visible consequence of AMD is the apparition of drusen between the retinal pigment epithelium and Bruch's membrane. We developed two automated drusen detectors based on the wavelet transform: a shape-based detector for hard drusen, and a texture- and color- based detector for soft drusen. Forty visual features were evaluated at the location of the automatically detected drusen. These features characterize the texture, the shape, the color, the spatial distribution, or the amount of drusen. A distance measure between twin pairs was defined for each visual feature; a smaller distance should be measured between monozygotic twins for visual features controlled by genetic factors. The predictions of several visual features (75.7% accuracy) are comparable or better than the predictions of human experts.

Quellec, Gwénolé; Abràmoff, Michael D.; Russell, Stephen R.

2010-03-01

327

The diagnostic significance of the multifocal pattern visual evoked potential in glaucoma.  

PubMed

The concept of objective perimetry is an exciting one because it strives to assess glaucoma damage without relying on psychophysical testing. The recent introduction of multifocal stimulus recording has enhanced our ability to examine the human visual field using electrophysiology. A multifocal pattern visual evoked potential can now be recorded, testing up to 60 sites within the central 25 degrees. The test requires only that the subject fixate on a target, while a cortically scaled dartboard pattern stimulus undergoes pseudorandom alternation within each of the test segments. In its present configuration the test requires at least 8 minutes recording time per eye. Modified bipolar electrode positions are required to ensure that adequate signals are detected from all parts of the visual field. In glaucoma patients, pattern visual evoked potential amplitudes have been shown to reflect visual field loss with reduction of signal amplitude in the affected areas. This technique represents the first major step toward objective detection of visual field defects in glaucoma. PMID:10537765

Graham, S L; Klistorner, A

1999-04-01

328

Model of visual contrast gain control and pattern masking  

NASA Technical Reports Server (NTRS)

We have implemented a model of contrast gain and control in human vision that incorporates a number of key features, including a contrast sensitivity function, multiple oriented bandpass channels, accelerating nonlinearities, and a devisive inhibitory gain control pool. The parameters of this model have been optimized through a fit to the recent data that describe masking of a Gabor function by cosine and Gabor masks [J. M. Foley, "Human luminance pattern mechanisms: masking experiments require a new model," J. Opt. Soc. Am. A 11, 1710 (1994)]. The model achieves a good fit to the data. We also demonstrate how the concept of recruitment may accommodate a variant of this model in which excitatory and inhibitory paths have a common accelerating nonlinearity, but which include multiple channels tuned to different levels of contrast.

Watson, A. B.; Solomon, J. A.

1997-01-01

329

Heuristic pattern search and its hybridization with simulated annealing for nonlinear global optimization  

Microsoft Academic Search

In this article, we present a new approach of hybrid simulated annealing method for minimizing multimodel functions called the simulated annealing heuristic pattern search (SAHPS) method. Two subsidiary methods are proposed to achieve the final form of the global search method, SAHPS. First, we introduce the approximate descent direction (ADD) method, which is a derivative-free procedure with high ability of

Abdel-Rahman Hedar; Masao Fukushima

2004-01-01

330

A tree structure frequent pattern mining algorithm based on hybrid search strategy and bitmap  

Microsoft Academic Search

This paper proposes a novel vertical format-based frequent pattern mining algorithm HBMFP. HBMFP adopts a hybrid search strategy of prefix-depth-first and depth-first searches based on the correlative array, which adequately makes use of the advantages of the both searches to effectively reduce yielded candidates as the same time keeps simplicity and lower memory cost. HBMFP uses bitmaps to store the

Mei Qiao; Liu Yang

2009-01-01

331

Patterned-String Tasks: Relation between Fine Motor Skills and Visual-Spatial Abilities in Parrots  

PubMed Central

String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla) and the cockatiel (Nymphicus hollandicus), forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.

Krasheninnikova, Anastasia

2013-01-01

332

Visual and spatial long-term memory: differential pattern of impairments in Williams and Down syndromes.  

PubMed

This purpose of this study was to investigate visual-object and visual-spatial long-term memory (LTM) abilities in individuals with Williams syndrome (WS) and Down syndrome (DS). Four groups comprised of 15 participants were included: WS group (10 males) with a mean chronological age (CA) of 18 years 5 months, SD 6 years 4 months, and mean mental age (MA) of 6 years 8 months, SD 1 year 5 months; WS control group (eight males) comprised of typically developing children (CA mean 6y 7mo, SD 8mo); DS group, (10 males, CA mean 16y 5mo, SD 5y 10mo; MA mean 5y 4mo, SD 8mo); and DS control group (seven males) formed by typically developing children (CA mean 5y 6mo, SD 7mo). In the WS and DS groups mental age and IQ were evaluated with the Form L-M of the Stanford-Binet Intelligence Scale. Results showed that individuals with WS showed decreased learning of visual-spatial material but substantially typical learning of visual-object patterns as compared to a group of mental-age-matched typically developing children. Individuals with DS showed the opposite profile, i.e. typical learning of visual-spatial sequences but impaired learning of visual-object patterns. These results, showing an interesting double dissociation between these two genetic syndromes in the learning of visual-object patterns as opposed to visual-spatial data, support the interpretation of learning disability* as a heterogeneous condition, characterized by potentially very different qualitative profiles of cognitive impairment. PMID:15892372

Vicari, Stefano; Bellucci, Samantha; Carlesimo, Giovanni Augusto

2005-05-01

333

Visual Signals Vertically Extend the Perceptual Span in Searching a Text: A Gaze-Contingent Window Study  

ERIC Educational Resources Information Center

This study investigated the effect of visual signals on perceptual span in text search and the kinds of signal information that facilitate the search. Participants were asked to find answers to specific questions in chapter-length texts in either a normal or a window condition, where the text disappeared beyond a vertical 3 degrees gaze-contingent…

Cauchard, Fabrice; Eyrolle, Helene; Cellier, Jean-Marie; Hyona, Jukka

2010-01-01

334

A theory and model to explain the variance in performance of visual search for ground vehicles in natural terrain  

Microsoft Academic Search

This research developed a theory and mathematical model explaining the variation in observers' visual search performance that can be attributed to computable properties of the image stimuli. The specific task is search for stationary military vehicles on natural terrain in narrow field of view images taken from the perspective of an observer on the ground, with vehicles in tactically appropriate

Gary Witus

2002-01-01

335

Spatial and temporal separation fails to counteract the effects of low prevalence in visual search  

PubMed Central

Recent research has shown that, in visual search, participants can miss 30–40% of targets when they only appear rarely (i.e. on 1–2% of trials). Low target prevalence alters the behavior of the searcher. It can lead participants to quit their search prematurely (Wolfe et al., 2005), to shift their decision criteria (Wolfe et al., 2007) and/or to make motor or response errors (Fleck & Mitroff, 2007). In this paper we examine whether the LP Effect can be ameliorated if we split the search set in two, spreading the task out over space and/or time. Observers searched for the letter “T” among “L”s. In Experiment 1, the left or right half of the display was presented to the participants before the second half. In Experiment 2, items were spatially intermixed but half of the items were presented first, followed by the second half. Experiment 3 followed the methods of Experiment 2 but allowed observers to correct perceived errors. All three experiments produced robust low prevalence (LP) effects with higher errors at 2% prevalence than at 50% prevalence. Dividing up the display had no beneficial effect on errors. The opportunity to correct errors reduced but did not eliminate the LP effect. Low prevalence continues to elevate errors even when observers are forced to slow down and permitted to correct errors.

Kunar, Melina A.; Rich, Anina N.; Wolfe, Jeremy M.

2011-01-01

336

An Analysis of Document Viewing Patterns of Web Search Engine Users  

Microsoft Academic Search

This chapter reviews the concepts of Web results page and Web page viewing patterns by users of Web search engines. It presents the advantages of using traditional transaction log analysis in identifying these patterns, serving as a basis for Web usage mining. The authors also present the results of a temporal of analysis of Web page viewing illustrating that the

Bernard J. Jansen; Amanda Spink

337

Fast-block-matching motion estimation algorithm using optimal search patterns  

NASA Astrophysics Data System (ADS)

For video compression, motion estimation is popularly employed to exploit temporal correlation existing in video sequences. If we employ the full search block matching algorithm for estimating motion vectors, it requires very heavy computational complexity. Although several fast block matching algorithms have been proposed to solve this problem, they sacrifice their reconstructed image quality. In this paper, we derive optimal search patterns for fast block matching motion estimation. By analyzing the block matching algorithm as a function of the block size and the shape, we find optimal search patterns for initial motion estimation. The proposed idea can provide an analytical ground for the current MPEG-2 proposals. In addition, we propose a new fast motion estimation algorithm using adaptive search patterns, considering matching criteria and statistical properties of object displacement. In order to select an appropriate search pattern, we exploit the relationship between the motion vector and the frame difference of each block. By changing the search pattern adaptively, we can improve the motion prediction accuracy, while reducing the required computational complexity compared to other fast block matching algorithms.

Lim, Dong-Keun; Ho, Yo-Sung

2000-12-01

338

Participation of the thalamofugal visual pathway in a coarse pattern discrimination task in an open arena.  

PubMed

The purpose of this study was to examine the role of the thalamofugal pathway in far-field visual processing. Experiment 1 examined the role of the visual wulst and the ectostriatum in a far-field pattern discrimination task in a large open arena. Control pigeons, pigeons with ectostriatum lesions, and pigeons with wulst lesions were trained to discriminate between four patterns within the arena. Ectostriatum-lesioned pigeons were unimpaired and behaved similar to controls. By contrast, wulst-lesioned pigeons were severely impaired in the pattern discrimination task in the open arena and performed poorer than control pigeons and pigeons with ectostriatum lesions. Statistical analyses of regional contributions to the observed impairment identified the left visual wulst and bilateral hyperstriatum ventrale, which lies outside the wulst, as interesting areas. To ensure that the impairment was not due to a general learning deficit, experiment 2 involved training the pigeons in a pattern discrimination task carried out in an operant chamber, which presumably required use of near-field visual information. Wulst-lesioned pigeons were able to learn the task and performed at a level no different from control pigeons. The results of these experiments support the proposal that the wulst may be important for processing far-field information. PMID:15265653

Budzynski, Cheri A; Bingman, Verner P

2004-08-31

339

Patterns of Visual Attention to Faces and Objects in Autism Spectrum Disorder  

ERIC Educational Resources Information Center

This study used eye-tracking to examine visual attention to faces and objects in adolescents with autism spectrum disorder (ASD) and typical peers. Point of gaze was recorded during passive viewing of images of human faces, inverted human faces, monkey faces, three-dimensional curvilinear objects, and two-dimensional geometric patterns.…

McPartland, James C.; Webb, Sara Jane; Keehn, Brandon; Dawson, Geraldine

2011-01-01

340

Stationary Pattern Adaptation and the Early Components in Human Visual Evoked Potentials.  

National Technical Information Service (NTIS)

Pattern-onset visual evoked potentials were elicited from humans by sinusoidal gratings of 0.5, 1, 2 and 4 cpd (cycles/degree) following adaptation to a blank field or one of the gratings. The wave forms recorded after blank field adaptation showed an ear...

H. K. Hudnell W. K. Boyes D. A. Otto

1990-01-01

341

Visualizing patterns of protein uptake to porous media using confocal scanning laser microscopy  

Microsoft Academic Search

Confocal scanning laser microscopy has been used to visualize the uptake of fluorescence-labeled proteins to porous stationary phases in finite bath adsorption experiments. Reference proteins were labeled with three different fluorescent dyes and a porous cation exchanger was sequentially incubated with solutions of these protein–dye conjugates. This sequential incubation experiment was used to investigate the pattern of protein uptake during

Thomas Linden; Anders Ljunglöf; Lars Hagel; Maria-Regina Kula; Jörg Thömmes

2002-01-01

342

Discovering interesting usage patterns in text collections: integrating text mining with visualization  

Microsoft Academic Search

This paper addresses the problem of making text mining results more comprehensible to humanities scholars, journalists, intelligence analysts, and other researchers, in order to support the analysis of text collections. Our system, FeatureLens, visualizes a text collection at several levels of granularity and enables users to explore interesting text patterns. The current implementation focuses on frequent itemsets of n-grams, as

Anthony Don; Elena Zheleva; Machon Gregory; Sureyya Tarkan; Loretta Auvil; Tanya Clement; Ben Shneiderman; Catherine Plaisant

2007-01-01

343

A little bit of history repeating: Splitting up multiple-target visual searches decreases second-target miss errors.  

PubMed

Visual searches with several targets in a display have been shown to be particularly prone to miss errors in both academic laboratory searches and professional searches such as radiology and baggage screening. Specifically, finding 1 target in a display can reduce the likelihood of detecting additional targets. This phenomenon was originally referred to as "satisfaction of search," but is referred to here as "subsequent search misses" (SSMs). SSM errors have been linked to a variety of causes, and recent evidence supports a working memory deficit wherein finding a target consumes working memory resources that would otherwise aid subsequent search for additional targets (Cain & Mitroff, 2013). The current study demonstrated that dividing 1 multiple-target search into several single-target searches, separated by three to five unrelated trials, effectively freed the working memory resources used by the found target and eliminated SSM errors. This effect was demonstrated with both university community participants and with professional visual searchers from the Transportation Security Administration, suggesting it may be a generally applicable technique for improving multiple-target visual search accuracy. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:24708353

Cain, Matthew S; Biggs, Adam T; Darling, Elise F; Mitroff, Stephen R

2014-06-01

344

Timing of saccadic eye movements during visual search for multiple targets  

PubMed Central

Visual search requires sequences of saccades. Many studies have focused on spatial aspects of saccadic decisions, while relatively few (e.g., Hooge & Erkelens, 1999) consider timing. We studied saccadic timing during search for targets (thin circles containing tilted lines) located among nontargets (thicker circles). Tasks required either (a) estimating the mean tilt of the lines, or (b) looking at targets without a concurrent psychophysical task. The visual similarity of targets and nontargets affected both the probability of hitting a target and the saccade rate in both tasks. Saccadic timing also depended on immediate conditions, specifically, (a) the type of currently fixated location (dwell time was longer on targets than nontargets), (b) the type of goal (dwell time was shorter prior to saccades that hit targets), and (c) the ordinal position of the saccade in the sequence. The results show that timing decisions take into account the difficulty of finding targets, as well as the cost of delays. Timing strategies may be a compromise between the attempt to find and locate targets, or other suitable landing locations, using eccentric vision (at the cost of increased dwell times) versus a strategy of exploring less selectively at a rapid rate.

Wu, Chia-Chien; Kowler, Eileen

2013-01-01

345

Timing of saccadic eye movements during visual search for multiple targets.  

PubMed

Visual search requires sequences of saccades. Many studies have focused on spatial aspects of saccadic decisions, while relatively few (e.g., Hooge & Erkelens, 1999) consider timing. We studied saccadic timing during search for targets (thin circles containing tilted lines) located among nontargets (thicker circles). Tasks required either (a) estimating the mean tilt of the lines, or (b) looking at targets without a concurrent psychophysical task. The visual similarity of targets and nontargets affected both the probability of hitting a target and the saccade rate in both tasks. Saccadic timing also depended on immediate conditions, specifically, (a) the type of currently fixated location (dwell time was longer on targets than nontargets), (b) the type of goal (dwell time was shorter prior to saccades that hit targets), and (c) the ordinal position of the saccade in the sequence. The results show that timing decisions take into account the difficulty of finding targets, as well as the cost of delays. Timing strategies may be a compromise between the attempt to find and locate targets, or other suitable landing locations, using eccentric vision (at the cost of increased dwell times) versus a strategy of exploring less selectively at a rapid rate. PMID:24049045

Wu, Chia-Chien; Kowler, Eileen

2013-01-01

346

Intelligent technique to search for patterns within images in massive databases  

SciTech Connect

An image retrieval system for JET has been developed. The image database contains the images of the JET high speed visible camera. The system input is a pattern selected inside an image and the output is the group of frames (defined by their discharge numbers and time slices) that show patterns similar to the selected one. This approach is based on morphological pattern recognition and it should be emphasized that the pattern is found independently of its location in the frame. The technique encodes images into characters and, therefore, it transforms the pattern search into a character-matching problem.

Vega, J.; Murari, A.; Pereira, A.; Portas, A.; Castro, P. [JET-EFDA, Culham Science Center, OX14 3DB Abingdon (United Kingdom)

2008-10-15

347

PatSearch: a program for the detection of patterns and structural motifs in nucleotide sequences  

PubMed Central

Regulation of gene expression at transcriptional and post-transcriptional level involves the interaction between short DNA or RNA tracts and the corresponding trans-acting protein factors. Detection of such cis-acting elements in genome-wide screenings may significantly contribute to genome annotation and comparative analysis as well as to target functional characterization experiments. We present here PatSearch, a flexible and fast pattern matcher able to search for specific combinations of oligonucleotide consensus sequences, secondary structure elements and position-weight matrices. It can also allow for mismatches/mispairings below a user fixed threshold. We report three different applications of the program in the search of complex patterns such as those of the iron responsive element hairpin-loop structure, the p53 responsive element and a promoter module containing CAAT-, TATA- and cap-boxes. PatSearch is available on the web at http://bighost.area.ba.cnr.it/BIG/PatSearch/.

Grillo, Giorgio; Licciulli, Flavio; Liuni, Sabino; Sbisa, Elisabetta; Pesole, Graziano

2003-01-01

348

Repetition Suppression and Multi-Voxel Pattern Similarity Differentially Track Implicit and Explicit Visual Memory  

PubMed Central

Repeated exposure to a visual stimulus is associated with corresponding reductions in neural activity, particularly within visual cortical areas. It has been argued that this phenomenon of repetition suppression is related to increases in processing fluency or implicit memory. However, repetition of a visual stimulus can also be considered in terms of the similarity of the pattern of neural activity elicited at each exposure—a measure that has recently been linked to explicit memory. Despite the popularity of each of these measures, direct comparisons between the two have been limited, and the extent to which they differentially (or similarly) relate to behavioral measures of memory has not been clearly established. In the present study, we compared repetition suppression and pattern similarity as predictors of both implicit and explicit memory. Using functional magnetic resonance imaging, we scanned 20 participants while they viewed and categorized repeated presentations of scenes. Repetition priming (facilitated categorization across repetitions) was used as a measure of implicit memory, and subsequent scene recognition was used as a measure of explicit memory. We found that repetition priming was predicted by repetition suppression in prefrontal, parietal, and occipitotemporal regions; however, repetition priming was not predicted by pattern similarity. In contrast, subsequent explicit memory was predicted by pattern similarity (across repetitions) in some of the same occipitotemporal regions that exhibited a relationship between priming and repetition suppression; however, explicit memory was not related to repetition suppression. This striking double dissociation indicates that repetition suppression and pattern similarity differentially track implicit and explicit learning.

Chun, Marvin M.; Kuhl, Brice A.

2013-01-01

349

“A Textbook Case Revisited”: Visual Rhetoric and Series Patterning in the American Museum of Natural History's Horse Evolution Displays  

Microsoft Academic Search

This article describes the development of visual rhetoric in a historically significant museum exhibit. The study documents rhetorical change in the museum's displays, specifically in visual series depicting the horse's evolutionary development. The study also exposes the purpose of series patterning in the renovated display and the multiple views on scientific visualization this display implies. Such an analysis suggests the

Jeremiah Dyehouse

2011-01-01

350

An instructive role for patterned spontaneous retinal activity in mouse visual map development  

PubMed Central

SUMMARY Complex neural circuits in the mammalian brain develop through a combination of genetic instruction and activity-dependent refinement. The relative role of these factors and the form of neuronal activity responsible for circuit development is a matter of significant debate. In the mammalian visual system, retinal ganglion cell projections to the brain are mapped with respect to retinotopic location and eye of origin. We manipulated the pattern of spontaneous retinal waves present during development without changing overall activity levels through the transgenic expression of ?2-nicotinic acetylcholine receptors in retinal ganglion cells of mice. We used this manipulation to demonstrate that spontaneous retinal activity is not just permissive, but instructive in the emergence of eye-specific segregation and retinotopic refinement in the mouse visual system. This suggests that specific patterns of spontaneous activity throughout the developing brain are essential in the emergence of specific and distinct patterns of neuronal connectivity.

Xu, Hong-ping; Furman, Moran; Mineur, Yann S.; Chen, Hui; King, Sarah L.; Zenisek, David; Zhou, Z. Jimmy; Butts, Daniel A.; Tian, Ning; Picciotto, Marina R.; Crair, Michael C.

2011-01-01

351

Visual Search and Target Cueing: A Comparison of Head-Mounted Versus Hand-Held Displays on the Allocation of Visual Attention.  

National Technical Information Service (NTIS)

We conducted a study to examine the effects of target cueing and conformality with a hand-held or head-mounted display to determine their effects on visual search tasks requiring focused and divided attention. Eleven military subjects were asked to detect...

M. Yeh C. D. Wickens

1998-01-01

352

Sleep and rest facilitate implicit memory in a visual search task  

PubMed Central

Several forms of learning have been demonstrated to show improvements with sleep. Based on rodent models, it has been suggested that replay of waking events in the hippocampus during sleep may underlie memory consolidation in humans. However, behavioral data for the role of sleep in human hippocampal-related memory have been inconsistent. To further investigate the role of sleep in hippocampal-mediated learning, we tested subjects in two sessions of a contextual cueing paradigm, a form of hippocampus-dependent implicit learning, separated by intervals of sleep, active wake, or carefully controlled quiet rest. Participants completed a visual search task, and unbeknown to them, some search displays were occasionally repeated in the experiment. Contextual cueing was revealed by faster search speed on repeated trials (Old) than unrepeated ones (New), even though subjects were unaware of the trial repetition. Notably, performance in a second testing session was equivalent for participants who underwent quiet resting, daytime sleep, or nocturnal sleep between the two sessions. These four groups showed equivalent transfer of learning from session 1. Notably, learning of new configurations in session 2 was absent in the active wake group, but was equally strong among the other three groups. These results indicate that this form of hippocampal learning is independent of sleep, and vulnerable to proactive interference during active wake. They prompt a reevaluation of the hippocampal replay hypothesis as a general model of sleep-dependent learning.

Mednick, SC; Makovski, T; Cai, DJ; Jiang, YV

2009-01-01

353

The role of within-dimension singleton priming in visual search.  

PubMed

The authors report a newly identified intertrial priming phenomenon, within-dimension singleton priming, by which search for a target that happens to be a singleton on the current trial is faster when the target on the previous trial had also been a singleton on the same dimension rather than a nonsingleton. This effect was replicated in 6 experiments with different procedures, with singletons on various dimensions, when the featural contrast defining the singleton remained the same or changed within a dimension from one trial to the next, and when the target was a singleton on a target-defining dimension or on an irrelevant dimension. These findings cannot be explained by previously demonstrated intertrial repetition effects such as dimension-specific priming or priming of pop-out. Theoretical implications of the within-dimension singleton priming phenomenon are discussed relative to the dimension-weighting hypothesis, the role of stimulus-driven salience in feature-guided search, and the roles of intertrial priming and goal-directed factors in visual search. PMID:18377170

Lamy, Dominique; Bar-Anan, Yoav; Egeth, Howard E

2008-04-01

354

Pattern reversal visual evoked potentials after alcohol administration among men at risk for alcoholism.  

PubMed

The P100 component of the pattern reversal visual evoked potential was used to compare men at high risk for alcoholism and control subjects before and after a low (0.5 g/kg) dose of ethanol. The high risk and control subjects did not differ in age, self-reported ethanol consumption, or estimates of ethanol metabolism rates, but changes in the occipital P100 latency differentiated them following ethanol administration. The P100 latency changes that distinguished high risk from control subjects were lateralized and provide preliminary evidence that perceptual visual stimulus processing is differentially affected in the two groups following ethanol administration. PMID:3237913

Pollock, V E; Volavka, J; Goodwin, D W; Gabrielli, W F; Mednick, S A; Knop, J; Schulsinger, F

1988-11-01

355

Pattern reversal visual evoked potential among men at risk for alcoholism.  

PubMed

The biological sons of male alcoholics, deemed to be at high risk (HR) for the development of alcoholism, were compared to control males, aged 18 to 21, using measures of the visual evoked potential elicited by checkerboard pattern reversal. Overall, the HR and control groups were not distinguished on the basis of visual evoked potential measures acquired from the occipital scalp region; however, when comparisons were restricted to right-handed subjects, the HR subjects showed more symmetry in a positive component with approximate latency of 242 ms compared with control subjects. The results are discussed in relation to hemispheric differences and alcoholism. PMID:3195352

Pollock, V E; Volavka, J; Gabrielli, W F; Mednick, S A; Knop, J; Goodwin, D W

1988-09-01

356

Case study of visualizing global user download patterns using Google Earth and NASA World Wind  

NASA Astrophysics Data System (ADS)

Geo-visualization is significantly changing the way we view spatial data and discover information. On the one hand, a large number of spatial data are generated every day. On the other hand, these data are not well utilized due to the lack of free and easily used data-visualization tools. This becomes even worse when most of the spatial data remains in the form of plain text such as log files. This paper describes a way of visualizing massive plain-text spatial data at no cost by utilizing Google Earth and NASA World Wind. We illustrate our methods by visualizing over 170,000 global download requests for satellite images maintained by the Earth Resources Observation and Science (EROS) Center of U.S. Geological Survey (USGS). Our visualization results identify the most popular satellite images around the world and discover the global user download patterns. The benefits of this research are: 1. assisting in improving the satellite image downloading services provided by USGS, and 2. providing a proxy for analyzing the "hot spot" areas of research. Most importantly, our methods demonstrate an easy way to geo-visualize massive textual spatial data, which is highly applicable to mining spatially referenced data and information on a wide variety of research domains (e.g., hydrology, agriculture, atmospheric science, natural hazard, and global climate change).

Zong, Ziliang; Job, Joshua; Zhang, Xuesong; Nijim, Mais; Qin, Xiao

2012-01-01

357

Spatial Attention can Bias Search in Visual Short-Term Memory  

PubMed Central

Whereas top-down attentional control is known to bias perceptual functions at many levels of stimulus analysis, its possible influence over memory-related functions remains uncharted. Our experiment combined behavioral measures and event-related potentials (ERPs) to test the ability of spatial orienting to bias functions associated with visual short-term memory (VSTM), and to shed light on the neural mechanisms involved. In particular, we investigated whether orienting attention to a spatial location within an array maintained in VSTM could facilitate the search for a specific remembered item. Participants viewed arrays of one, two or four differently colored items, followed by an informative spatial (100% valid) or uninformative neutral retro-cue (1500–2500?ms after the array), and later by a probe stimulus (500–1000?ms after the retro-cue). The task was to decide whether the probe stimulus had been present in the array. Behavioral results showed that spatial retro-cues improved both accuracy and response times for making decisions about the presence of the probe item in VSTM, and significantly attenuated performance decrements caused by increasing VSTM load. We also identified a novel ERP component (N3RS) specifically associated with searching for an item within VSTM. Paralleling the behavioral results, the amplitude and duration of the N3RS systematically increased with VSTM load in neutral retro-cue trials. When spatial retro-cues were provided, this “retro-search” component was absent. Our findings clearly show that the influence of top-down attentional biases extends to mnemonic functions, and, specifically, that searching for items within VSTM can be under flexible voluntary control.

Nobre, Anna C.; Griffin, Ivan C.; Rao, Anling

2007-01-01

358

Neural evidence for distracter suppression during visual search in real-world scenes.  

PubMed

Selecting visual information from cluttered real-world scenes involves the matching of visual input to the observer's attentional set--an internal representation of objects that are relevant for current behavioral goals. When goals change, a new attentional set needs to be instantiated, requiring the suppression of the previous set to prevent distraction by objects that are no longer relevant. In the present fMRI study, we investigated how such suppression is implemented at the neural level. We measured human brain activity in response to natural scene photographs that could contain objects from (1) a currently relevant (target) category, (2) a previously but not presently relevant (distracter) category, and/or (3) a never relevant (neutral) category. Across conditions, multivoxel response patterns in object-selective cortex carried information about objects present in the scenes. However, this information strongly depended on the task relevance of the objects. As expected, information about the target category was significantly increased relative to the neutral category, indicating top-down enhancement of task-relevant information. Importantly, information about the distracter category was significantly reduced relative to the neutral category, indicating that the processing of previously relevant objects was suppressed. Such active suppression at the level of high-order visual cortex may serve to prevent the erroneous selection of, or interference from, objects that are no longer relevant to ongoing behavior. We conclude that the enhancement of relevant information and the suppression of distracting information both contribute to the efficient selection of visual information from cluttered real-world scenes. PMID:22915122

Seidl, Katharina N; Peelen, Marius V; Kastner, Sabine

2012-08-22

359

Visual pattern discrimination by population retinal ganglion cells' activities during natural movie stimulation.  

PubMed

In the visual system, neurons often fire in synchrony, and it is believed that synchronous activities of group neurons are more efficient than single cell response in transmitting neural signals to down-stream neurons. However, whether dynamic natural stimuli are encoded by dynamic spatiotemporal firing patterns of synchronous group neurons still needs to be investigated. In this paper we recorded the activities of population ganglion cells in bullfrog retina in response to time-varying natural images (natural scene movie) using multi-electrode arrays. In response to some different brief section pairs of the movie, synchronous groups of retinal ganglion cells (RGCs) fired with similar but different spike events. We attempted to discriminate the movie sections based on temporal firing patterns of single cells and spatiotemporal firing patterns of the synchronous groups of RGCs characterized by a measurement of subsequence distribution discrepancy. The discrimination performance was assessed by a classification method based on Support Vector Machines. Our results show that different movie sections of the natural movie elicited reliable dynamic spatiotemporal activity patterns of the synchronous RGCs, which are more efficient in discriminating different movie sections than the temporal patterns of the single cells' spike events. These results suggest that, during natural vision, the down-stream neurons may decode the visual information from the dynamic spatiotemporal patterns of the synchronous group of RGCs' activities. PMID:24465283

Zhang, Ying-Ying; Wang, Ru-Bin; Pan, Xiao-Chuan; Gong, Hai-Qing; Liang, Pei-Ji

2014-02-01

360

A Convergence Analysis of Unconstrained and Bound Constrained Evolutionary Pattern Search  

SciTech Connect

The authors present and analyze a class of evolutionary algorithms for unconstrained and bound constrained optimization on R{sup n}: evolutionary pattern search algorithms (EPSAs). EPSAs adaptively modify the step size of the mutation operator in response to the success of previous optimization steps. The design of EPSAs is inspired by recent analyses of pattern search methods. They show that EPSAs can be cast as stochastic pattern search methods, and they use this observation to prove that EpSAs have a probabilistic weak stationary point convergence theory. This work provides the first convergence analysis for a class of evolutionary algorithms that guarantees convergence almost surely to a stationary point of a nonconvex objective function.

Hart, W.E.

1999-04-22

361

Premenstrual enhancement of snake detection in visual search in healthy women  

PubMed Central

It is well known that adult humans detect images of snakes as targets more quickly than images of flowers as targets whether the images are in color or gray-scale. When such visual searches were performed by a total of 60 adult premenopausal healthy women in the present study to examine whether their performance would fluctuate across the phases of the menstrual cycle, snake detection was found to become temporarily enhanced during the luteal phase as compared to early or late follicular phases. This is the first demonstration of the existence of within-individual variation of the activity of the fear module, as a predictable change in cognitive strength, which appears likely to be due to the hormonal changes that occur in the menstrual cycle of healthy women.

Masataka, N.; Shibasaki, M.

2012-01-01

362

HSI-Find: A Visualization and Search Service for Terascale Spectral Image Catalogs  

NASA Astrophysics Data System (ADS)

Imaging spectrometers are remote sensing instruments commonly deployed on aircraft and spacecraft. They provide surface reflectance in hundreds of wavelength channels, creating data cubes known as hyperspecrtral images. They provide rich compositional information making them powerful tools for planetary and terrestrial science. These data products can be challenging to interpret because they contain datapoints numbering in the thousands (Dawn VIR) or millions (AVIRIS-C). Cross-image studies or exploratory searches involving more than one scene are rare; data volumes are often tens of GB per image and typical consumer-grade computers cannot store more than a handful of images in RAM. Visualizing the information in a single scene is challenging since the human eye can only distinguish three color channels out of the hundreds available. To date, analysis has been performed mostly on single images using purpose-built software tools that require extensive training and commercial licenses. The HSIFind software suite provides a scalable distributed solution to the problem of visualizing and searching large catalogs of spectral image data. It consists of a RESTful web service that communicates to a javascript-based browser client. The software provides basic visualization through an intuitive visual interface, allowing users with minimal training to explore the images or view selected spectra. Users can accumulate a library of spectra from one or more images and use these to search for similar materials. The result appears as an intensity map showing the extent of a spectral feature in a scene. Continuum removal can isolate diagnostic absorption features. The server-side mapping algorithm uses an efficient matched filter algorithm that can process a megapixel image cube in just a few seconds. This enables real-time interaction, leading to a new way of interacting with the data: the user can launch a search with a single mouse click and see the resulting map in seconds. This allows the user to quickly explore each image, ascertain the main units of surface material, localize outliers, and develop an understanding of the various materials' spectral characteristics. The HSIFind software suite is currently in beta testing at the Planetary Science Institute and a process is underway to release it under an open source license to the broader community. We believe it will benefit instrument operations during remote planetary exploration, where tactical mission decisions demand rapid analysis of each new dataset. The approach also holds potential for public spectral catalogs where its shallow learning curve and portability can make these datasets accessible to a much wider range of researchers. Acknowledgements: The HSIFind project acknowledges the NASA Advanced MultiMission Operating System (AMMOS) and the Multimission Ground Support Services (MGSS). E. Palmer is with the Planetary Science Institute, Tucson, AZ. Other authors are with the Jet Propulsion Laboratory, Pasadena, CA. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration. Copyright 2013, California Institute of Technology.

Thompson, D. R.; Smith, A. T.; Castano, R.; Palmer, E. E.; Xing, Z.

2013-12-01

363

Visual Search as a Tool for a Quick and Reliable Assessment of Cognitive Functions in Patients with Multiple Sclerosis  

PubMed Central

Background Despite the high frequency of cognitive impairment in multiple sclerosis, its assessment has not gained entrance into clinical routine yet, due to lack of time-saving and suitable tests for patients with multiple sclerosis. Objective The aim of the study was to compare the paradigm of visual search with neuropsychological standard tests, in order to identify the test that discriminates best between patients with multiple sclerosis and healthy individuals concerning cognitive functions, without being susceptible to practice effects. Methods Patients with relapsing remitting multiple sclerosis (n = 38) and age-and gender-matched healthy individuals (n = 40) were tested with common neuropsychological tests and a computer-based visual search task, whereby a target stimulus has to be detected amongst distracting stimuli on a touch screen. Twenty-eight of the healthy individuals were re-tested in order to determine potential practice effects. Results Mean reaction time reflecting visual attention and movement time indicating motor execution in the visual search task discriminated best between healthy individuals and patients with multiple sclerosis, without practice effects. Conclusions Visual search is a promising instrument for the assessment of cognitive functions and potentially cognitive changes in patients with multiple sclerosis thanks to its good discriminatory power and insusceptibility to practice effects.

Utz, Kathrin S.; Hankeln, Thomas M. A.; Jung, Lena; Lammer, Alexandra; Waschbisch, Anne; Lee, De-Hyung; Linker, Ralf A.; Schenk, Thomas

2013-01-01

364

Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns  

NASA Technical Reports Server (NTRS)

Various flow visualization techniques were used to define the seondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious. Previously announced in STAR as N83-14435

Gaugler, R. E.; Russell, L. M.

1984-01-01

365

A search for wide visual companions of exoplanet host stars: The Calar Alto Survey  

NASA Astrophysics Data System (ADS)

We have carried out a search for co-moving stellar and substellar companions around 18 exoplanet host stars with the infrared camera MAGIC at the 2.2 m Calar Alto telescope, by comparing our images with images from the all sky surveys 2MASS, POSS I and II. Four stars of the sample namely HD 80606, 55 Cnc, HD 46375 and BD-10°3166, are listed as binaries in the Washington Visual Double Star Catalogue (WDS). The binary nature of HD 80606, 55 Cnc, and HD 46375 is confirmed with both astrometry as well as photometry, thereby the proper motion of the companion of HD 46375 was determined here for the first time. We derived the companion masses as well as the longterm stability regions for additional companions in these three binary systems. We can rule out further stellar companions around all stars in the sample with projected separations between 270 AU and 2500 AU, being sensitive to substellar companions with masses down to ˜ 60 {MJup} (S/N=3). Furthermore we present evidence that the two components of the WDS binary BD-10°3166 are unrelated stars, i.e this system is a visual pair. The spectrophotometric distance of the primary (a K0 dwarf) is ˜ 67 pc, whereas the presumable secondary BD-10°3166 B (a M4 to M5 dwarf) is located at a distance of 13 pc in the foreground.

Mugrauer, M.; Neuhäuser, R.; Mazeh, T.; Guenther, E.; Fernández, M.; Broeg, C.

2006-05-01

366

Active training and driving-specific feedback improve older drivers' visual search prior to lane changes  

PubMed Central

Background Driving retraining classes may offer an opportunity to attenuate some effects of aging that may alter driving skills. Unfortunately, there is evidence that classroom programs (driving refresher courses) do not improve the driving performance of older drivers. The aim of the current study was to evaluate if simulator training sessions with video-based feedback can modify visual search behaviors of older drivers while changing lanes in urban driving. Methods In order to evaluate the effectiveness of the video-based feedback training, 10 older drivers who received a driving refresher course and feedback about their driving performance were tested with an on-road standardized evaluation before and after participating to a simulator training program (Feedback group). Their results were compared to a Control group (12 older drivers) who received the same refresher course and in-simulator active practice as the Feedback group without receiving driving-specific feedback. Results After attending the training program, the Control group showed no increase in the frequency of the visual inspection of three regions of interests (rear view and left side mirrors, and blind spot). In contrast, for the Feedback group, combining active training and driving-specific feedbacks increased the frequency of blind spot inspection by 100% (32.3 to 64.9% of verification before changing lanes). Conclusions These results suggest that simulator training combined with driving-specific feedbacks helped older drivers to improve their visual inspection strategies, and that in-simulator training transferred positively to on-road driving. In order to be effective, it is claimed that driving programs should include active practice sessions with driving-specific feedbacks. Simulators offer a unique environment for developing such programs adapted to older drivers' needs.

2012-01-01

367

The Effect of Stimulus Duration and Motor Response in Hemispatial Neglect during a Visual Search Task  

PubMed Central

Patients with hemispatial neglect exhibit a myriad of profound deficits. A hallmark of this syndrome is the patients' absence of awareness of items located in their contralesional space. Many studies, however, have demonstrated that neglect patients exhibit some level of processing of these neglected items. It has been suggested that unconscious processing of neglected information may manifest as a fast denial. This theory of fast denial proposes that neglected stimuli are detected in the same way as non-neglected stimuli, but without overt awareness. We evaluated the fast denial theory by conducting two separate visual search task experiments, each differing by the duration of stimulus presentation. Specifically, in Experiment 1 each stimulus remained in the participants' visual field until a response was made. In Experiment 2 each stimulus was presented for only a brief duration. We further evaluated the fast denial theory by comparing verbal to motor task responses in each experiment. Overall, our results from both experiments and tasks showed no evidence for the presence of implicit knowledge of neglected stimuli. Instead, patients with neglect responded the same when they neglected stimuli as when they correctly reported stimulus absence. These findings thus cast doubt on the concept of the fast denial theory and its consequent implications for non-conscious processing. Importantly, our study demonstrated that the only behavior affected was during conscious detection of ipsilesional stimuli. Specifically, patients were slower to detect stimuli in Experiment 1 compared to Experiment 2, suggesting a duration effect occurred during conscious processing of information. Additionally, reaction time and accuracy were similar when reporting verbally versus motorically. These results provide new insights into the perceptual deficits associated with neglect and further support other work that falsifies the fast denial account of non-conscious processing in hemispatial visual neglect.

Jelsone-Swain, Laura M.; Smith, David V.; Baylis, Gordon C.

2012-01-01

368

Cortical metabolic activity matches the pattern of visual suppression in strabismus.  

PubMed

When an eye becomes deviated in early childhood, a person does not experience double vision, although the globes are aimed at different targets. The extra image is prevented from reaching perception in subjects with alternating exotropia by suppression of each eye's peripheral temporal retina. To test the impact of visual suppression on neuronal activity in primary (striate) visual cortex, the pattern of cytochrome oxidase (CO) staining was examined in four macaques raised with exotropia by disinserting the medial rectus muscles shortly following birth. No ocular dominance columns were visible in opercular cortex, where the central visual field is represented, indicating that signals coming from the central retina in each eye were perceived. However, the border strips at the edges of ocular dominance columns appeared pale, reflecting a loss of activity in binocular cells from disruption of fusion. In calcarine cortex, where the peripheral visual field is represented, there were alternating pale and dark bands resembling ocular dominance columns. To interpret the CO staining pattern, [(3)H]proline was injected into the right eye in two monkeys. In the right calcarine cortex, the pale CO columns matched the labeled proline columns of the right eye. In the left calcarine cortex, the pale CO columns overlapped the unlabeled columns of the left eye in the autoradiograph. Therefore, metabolic activity was reduced in the ipsilateral eye's ocular dominance columns which serve peripheral temporal retina, in a fashion consistent with the topographic organization of suppression scotomas in humans with exotropia. PMID:23447587

Adams, Daniel L; Economides, John R; Sincich, Lawrence C; Horton, Jonathan C

2013-02-27

369

CORTICAL METABOLIC ACTIVITY MATCHES THE PATTERN OF VISUAL SUPPRESSION IN STRABISMUS  

PubMed Central

When an eye becomes deviated in early childhood a person does not experience double vision, although the globes are aimed at different targets. The extra image is prevented from reaching perception in subjects with alternating exotropia by suppression of each eye’s peripheral temporal retina. To test the impact of visual suppression on neuronal activity in primary (striate) visual cortex, the pattern of cytochrome oxidase (CO) staining was examined in four macaques raised with exotropia by disinserting the medial rectus muscles shortly following birth. No ocular dominance columns were visible in opercular cortex, where the central visual field is represented, indicating that signals coming from the central retina in each eye were perceived. However, the border strips at the edges of ocular dominance columns appeared pale, reflecting a loss of activity in binocular cells from disruption of fusion. In calcarine cortex, where the peripheral visual field is represented, there were alternating pale and dark bands resembling ocular dominance columns. To interpret the CO staining pattern, [3H]proline was injected into the right eye in two monkeys. In the right calcarine cortex, the pale CO columns matched the labeled proline columns of the right eye. In the left calcarine cortex, the pale CO columns overlapped the unlabeled columns of the left eye in the autoradiograph. Therefore, metabolic activity was reduced in the ipsilateral eye’s ocular dominance columns which serve peripheral temporal retina, in a fashion consistent with the topographic organization of suppression scotomas in humans with exotropia.

Adams, Daniel L.; Economides, John R.; Sincich, Lawrence C.; Horton, Jonathan C.

2013-01-01

370

Multi-voxel patterns of visual category representation during episodic encoding are predictive of subsequent memory  

PubMed Central

Successful encoding of episodic memories is thought to depend on contributions from prefrontal and temporal lobe structures. Neural processes that contribute to successful encoding have been extensively explored through univariate analyses of neuroimaging data that compare mean activity levels elicited during the encoding of events that are subsequently remembered vs. those subsequently forgotten. Here, we applied pattern classification to fMRI data to assess the degree to which distributed patterns of activity within prefrontal and temporal lobe structures elicited during the encoding of word-image pairs were diagnostic of the visual category (Face or Scene) of the encoded image. We then assessed whether representation of category information was predictive of subsequent memory. Classification analyses indicated that temporal lobe structures contained information robustly diagnostic of visual category. Information in prefrontal cortex was less diagnostic of visual category, but was nonetheless associated with highly reliable classifier-based evidence for category representation. Critically, trials associated with greater classifier-based estimates of category representation in temporal and prefrontal regions were associated with a higher probability of subsequent remembering. Finally, consideration of trial-by-trial variance in classifier-based measures of category representation revealed positive correlations between prefrontal and temporal lobe representations, with the strength of these correlations varying as a function of the category of image being encoded. Together, these results indicate that multi-voxel representations of encoded information can provide unique insights into how visual experiences are transformed into episodic memories.

Kuhl, Brice A.; Rissman, Jesse; Wagner, Anthony D.

2012-01-01

371

Investigation of Attentional Bias in Obsessive Compulsive Disorder with and without Depression in Visual Search  

PubMed Central

Whether Obsessive Compulsive Disorder (OCD) is associated with an increased attentional bias to emotive stimuli remains controversial. Additionally, it is unclear whether comorbid depression modulates abnormal emotional processing in OCD. This study examined attentional bias to OC-relevant scenes using a visual search task. Controls, non-depressed and depressed OCD patients searched for their personally selected positive images amongst their negative distractors, and vice versa. Whilst the OCD groups were slower than healthy individuals in rating the images, there were no group differences in the magnitude of negative bias to concern-related scenes. A second experiment employing a common set of images replicated the results on an additional sample of OCD patients. Although there was a larger bias to negative OC-related images without pre-exposure overall, no group differences in attentional bias were observed. However, OCD patients subsequently rated the images more slowly and more negatively, again suggesting post-attentional processing abnormalities. The results argue against a robust attentional bias in OCD patients, regardless of their depression status and speak to generalized difficulties disengaging from negative valence stimuli. Rather, post-attentional processing abnormalities may account for differences in emotional processing in OCD.

Morein-Zamir, Sharon; Papmeyer, Martina; Durieux, Alice; Fineberg, Naomi A.; Sahakian, Barbara J.; Robbins, Trevor W.

2013-01-01

372

Event-related potentials dissociate perceptual from response-related age effects in visual search.  

PubMed

Attentional decline plays a major role in cognitive changes with aging. However, which specific aspects of attention contribute to this decline is as yet little understood. To identify the contributions of various potential sources of age decrements in visual search, we combined response time measures with lateralized event-related potentials of younger and older adults performing a compound-search task, in which the target-defining dimension of a pop-out target (color/shape) and the response-critical target feature (vertical/horizontal stripes) varied independently across trials. Slower responses in older participants were associated with age differences in all analyzed event-related potentials from perception to response, indicating that behavioral slowing originates from multiple stages within the information-processing stream. Furthermore, analyses of carry-over effects from one trial to the next revealed repetition facilitation of the target-defining dimension and of the motor response-originating from preattentive perceptual and motor execution stages, respectively-to be independent of age. Critically, we demonstrated specific age deficits on intermediate processing stages when intertrial changes required more executively controlled processes, such as flexible stimulus-response (re-)mapping across trials. PMID:22921866

Wiegand, Iris; Finke, Kathrin; Müller, Hermann J; Töllner, Thomas

2013-03-01

373

Hide and seek: the theory of mind of visual concealment and search.  

PubMed

Researchers have investigated visual search behavior for almost a century. During that time, few studies have examined the cognitive processes involved in hiding items rather than finding them. To investigate this, we developed a paradigm that allowed participants to indicate where they would hide (or find) an item that was to be found (or hidden) by a friend or a foe. We found that (i) for friends more than foes, participants selected the pop-out item in the display, and (ii) when the display was homogeneous, they selected nearby and corner items. These behaviors held for both hiding and finding, although hide and find behaviors were not identical. For pop-out displays, decision times were unusually long when hiding an item from a foe. These data converge on the conclusion that the principles of search and concealment are similar, but not the same. They also suggest that this paradigm will provide researchers a powerful method for investigating theory of mind in adults. PMID:24722955

Anderson, Giles M; Foulsham, Tom; Nasiopoulos, Eleni; Chapman, Craig S; Kingstone, Alan

2014-05-01

374

The effect of midazolam on visual search: Implications for understanding amnesia  

PubMed Central

The notion of multiple memory systems based on conscious accessibility has been supported largely by neuropsychological patient studies. Specifically, it was widely held that amnesic patients have impaired explicit memory performance but spared implicit memory performance. However, recent patient studies have called the implicit/explicit memory distinction into question. In this study, normal participants were tested on a visual search task, once after an injection of midazolam, an anesthetic that induces temporary amnesia, and once after an injection of saline. Under the influence of midazolam, participants did not show facilitation in search times for repeated configurations (contextual cuing), although there was a general speed-up in performance across blocks in both the midazolam and saline conditions. Neither the contextual-cuing effect nor the procedural-learning effect was available to subjective experience, yet only one of these was affected by midazolam-induced amnesia. These data call into question the notion that memory systems divide on the basis of subjective experience of consciousness or reportability. Rather, the findings support the contention that anterograde amnesia affects learning that depends on building novel associations in memory and that this deficit does not hinge upon accessibility to consciousness.

Park, Heekyeong; Quinlan, Joseph; Thornton, Edward; Reder, Lynne M.

2004-01-01

375

Accounting for anatomical noise in SPECT with a visual-search human-model observer  

NASA Astrophysics Data System (ADS)

Reliable human-model observers for clinically realistic detection studies are of considerable interest in medical imaging research, but current model observers require frequent revalidation with human data. A visual-search (VS) observer framework may improve reliability by better simulating realistic etection-localization tasks. Under this framework, model observers execute a holistic search to identify tumor-like candidates and then perform careful analysis of these candidates. With emission tomography, anatomical noise in the form of elevated uptake in neighboring tissue often complicates the task. Some scanning model observers simulate the human ability to read around such noise by presubtracting the mean normal background from the test image, but this backgroundknown- exactly (BKE) assumption has several drawbacks. The extent to which the VS observer can overcome these drawbacks was investigated by comparing it against humans and a scanning observer for detection of solitary pulmonary nodules in a simulated SPECT lung study. Our results indicate that the VS observer offers a robust alternative to the scanning observer for modeling humans.

Gifford, H. C.; King, M. A.; Smyczynski, M. S.

2011-03-01

376

Performance characteristics of a visual-search human-model observer with sparse PET image data  

NASA Astrophysics Data System (ADS)

As predictors of human performance in detection-localization tasks, statistical model observers can have problems with tasks that are primarily limited by target contrast or structural noise. Model observers with a visual-search (VS) framework may provide a more reliable alternative. This framework provides for an initial holistic search that identifies suspicious locations for analysis by a statistical observer. A basic VS observer for emission tomography focuses on hot "blobs" in an image and uses a channelized nonprewhitening (CNPW) observer for analysis. In [1], we investigated this model for a contrast-limited task with SPECT images; herein, a statisticalnoise limited task involving PET images is considered. An LROC study used 2D image slices with liver, lung and soft-tissue tumors. Human and model observers read the images in coronal, sagittal and transverse display formats. The study thus measured the detectability of tumors in a given organ as a function of display format. The model observers were applied under several task variants that tested their response to structural noise both at the organ boundaries alone and over the organs as a whole. As measured by correlation with the human data, the VS observer outperformed the CNPW scanning observer.

Gifford, Howard C.

2012-02-01

377

The Effect of Information Forms and Floating Advertisements for Visual Search on Web Pages: An Eye-Tracking Study  

Microsoft Academic Search

Users’ visual search on a Web page is impacted by information forms, information layout, Internet advertisements (ads for\\u000a short), etc. Text and picture are two important forms of expressing the information on Web pages, and it is generally through\\u000a the two forms of title that users can search their desired information. This study investigates the effect of the two basic

Mi Li; Jingjing Yin; Shengfu Lu; Ning Zhong

2009-01-01

378

Discrimination of the local orientation structure of spiral Glass patterns early in human visual cortex.  

PubMed

The local orientation structure of a visual image is fundamental to the perception of spatial form. Reports of reliable orientation-selective modulations in the pattern of fMRI activity have demonstrated the potential for investigating the representation of orientation in the human visual cortex. Orientation-selective voxel responses could arise from anisotropies in the preferred orientations of pooled neurons due to the random sampling of the cortical surface. However, it is unclear whether orientation-selective voxel responses reflect biases in the underlying distribution of neuronal orientation preference, such as the demonstrated over-representation of radial orientations (those collinear with fixation). Here, we investigated whether stimuli balanced in their radial components could evoke orientation-selective biases in voxel activity. We attempted to discriminate the sense of spiral Glass patterns (opening anti-clockwise or clockwise), in which the local orientation structure was defined by the placement of paired dots at an orientation offset from the radial. We found that information within the spatial pattern of fMRI responses in each of V1, V2, V3, and V3A/B allowed discrimination of the spiral sense with accuracies significantly above chance. This result demonstrates that orientation-selective voxel responses can arise without the influence of a radial bias. Furthermore, the finding indicates the importance of the early visual areas in representing the local orientation structure for the perception of complex spatial form. PMID:19385017

Mannion, D J; McDonald, J S; Clifford, C W G

2009-06-01

379

Case study of visualizing global user download patterns using Google Earth and NASA World Wind  

SciTech Connect

Geo-visualization is significantly changing the way we view spatial data and discover information. On the one hand, a large number of spatial data are generated every day. On the other hand, these data are not well utilized due to the lack of free and easily used data-visualization tools. This becomes even worse when most of the spatial data remains in the form of plain text such as log files. This paper describes a way of visualizing massive plain-text spatial data at no cost by utilizing Google Earth and NASAWorld Wind. We illustrate our methods by visualizing over 170,000 global download requests for satellite images maintained by the Earth Resources Observation and Science (EROS) Center of U.S. Geological Survey (USGS). Our visualization results identify the most popular satellite images around the world and discover the global user download patterns. The benefits of this research are: 1. assisting in improving the satellite image downloading services provided by USGS, and 2. providing a proxy for analyzing the hot spot areas of research. Most importantly, our methods demonstrate an easy way to geovisualize massive textual spatial data, which is highly applicable to mining spatially referenced data and information on a wide variety of research domains (e.g., hydrology, agriculture, atmospheric science, natural hazard, and global climate change).

Zong, Ziliang; Job, Joshua; Zhang, Xuesong; Nijim, Mais; Qin, Xiao

2012-10-09

380

Differential expression patterns of occ1-related genes in adult monkey visual cortex.  

PubMed

We have previously revealed that occ1 is preferentially expressed in the primary visual area (V1) of the monkey neocortex. In our attempt to identify more area-selective genes in the macaque neocortex, we found that testican-1, an occ1-related gene, and its family members also exhibit characteristic expression patterns along the visual pathway. The expression levels of testican-1 and testican-2 mRNAs as well as that of occ1 mRNA start of high in V1, progressively decrease along the ventral visual pathway, and end of low in the temporal areas. Complementary to them, the neuronal expression of SPARC mRNA is abundant in the association areas and scarce in V1. Whereas occ1, testican-1, and testican-2 mRNAs are preferentially distributed in thalamorecipient layers including "blobs," SPARC mRNA expression avoids these layers. Neither SC1 nor testican-3 mRNA expression is selective to particular areas, but SC1 mRNA is abundantly observed in blobs. The expressions of occ1, testican-1, testican-2, and SC1 mRNA were downregulated after monocular tetrodotoxin injection. These results resonate with previous works on chemical and functional gradients along the primate occipitotemporal visual pathway and raise the possibility that these gradients and functional architecture may be related to the visual activity-dependent expression of these extracellular matrix glycoproteins. PMID:19073625

Takahata, Toru; Komatsu, Yusuke; Watakabe, Akiya; Hashikawa, Tsutomu; Tochitani, Shiro; Yamamori, Tetsuo

2009-08-01

381

Integrating MPEG7 Descriptors and Pattern Recognition: An Environment for Multimedia Indexing and Searching  

Microsoft Academic Search

This paper describes a music searching system based on an automatic indexing process created over a pattern recognition tool and MPEG-7 standard. We present a complete analysis of the involved technologies integration process and show a reference measure in the feasibility of this kind of application not only in the research environment but also in the production of real systems.

Reinaldo Matushima; Daniel Makoto Hiramatsu; Regina Melo Silveira; Wilson Vicente Ruggiero; Carlos Eduardo Machado Da Costa; Mauricio Mario Monteiro; Celso Hatori

2004-01-01

382

Visually-evoked pattern and photomyoclonic responses in video game and television epilepsy: case reports.  

PubMed

This research paper reports a case study of two male photosensitive epileptic patients, aged 14 and 16 years old respectively, whose epileptic seizures were often triggered by the flickers from television and video games respectively. The 14-year old patient had no family history of epilepsy, while the 16 year old had a family history of epilepsy. A comprehensive electroencephalogram (EEG), including hyperventilation, intermittent photic stimulation (IPS) and pattern stimulation were carried out on them and EEG abnormalities including photoparoxysmal responses (PPR) and generalized myoclonic responses were evoked. A thorough analysis of the EEG morphology of the myclonic responses and the clinical manifestations showed evidence of two separate entitles of seizures namely: visually evoked pattern-myoclonic responses (PTMR) and visually evoked photomyoclonic responses (PMR). PTMR was independent of flash rate and occurred before a PPR and at the same time as the flash rate, while PMR occurred after the PPR and was dependent on flash rate. These findings suggest that "Video Game" epilepsy is probably a pattern sensitive epilepsy, electronic screen being the source of the triggering patterns; hence, the morphology and the family histories and the myoclonic phenomena differ from those of pure photosensitive epilepsy. PMID:9201318

Anyanwu, E; Watson, N A

1996-01-01

383

Visual information and multi-joint coordination patterns in one-leg stance.  

PubMed

This study examined the influence of visual information on the multi-joint coordination patterns in maintaining one-leg stance. 12 participants stood still on their left leg for two 1 min trials with and without visual information. The multi-joint coordination patterns in the frontal plane were examined using a frequency domain principal component analysis (PCAf) on 14 joint angular motion time series. The factor loading spectra of PC1 showed two distinct multi-joint postural coordination strategies that relate to the mechanical constraints on balance identified by Hof (2007) [7]. The more prevalent strategy was the coordination of the left ankle-left knee or the left ankle only motion that is related to the "moving the center of pressure" strategy. A 2nd multi-joint coordination strategy showed larger factor loading of the trunk and upper limbs (i.e., shoulders and elbows) in addition to the left ankle implying the role of the upper limbs to generate "counter-rotational torque against the sway of the center of mass (COM)". With eyes open, the participants predominantly utilized the 1st strategy to maintain balance but switched to the 2nd strategy when visual information was not available during the stance. The role of visual information in determining the prevalence of two dominant multi-joint coordination kinematic patterns in one-leg stance reflects the redundant and emergent properties of the postural control system that channel the biomechanical constraints on balance arising from the interaction of the task, environment and the individual. PMID:24388780

Wang, Zheng; Molenaar, Peter C M; Challis, John H; Jordan, Kimberlee; Newell, Karl M

2014-03-01

384

Effects of Mora Deletion, Nonword Repetition, Rapid Naming, and Visual Search Performance on Beginning Reading in Japanese  

ERIC Educational Resources Information Center

This study examined the extent to which mora deletion (phonological analysis), nonword repetition (phonological memory), rapid automatized naming (RAN), and visual search abilities predict reading in Japanese kindergartners and first graders. Analogous abilities have been identified as important predictors of reading skills in alphabetic languages…

Kobayashi, Maya Shiho; Haynes, Charles W.; Macaruso, Paul; Hook, Pamela E.; Kato, Junko

2005-01-01

385

How Prior Knowledge and Colour Contrast Interfere Visual Search Processes in Novice Learners: An Eye Tracking Study  

ERIC Educational Resources Information Center

This study investigates how prior content knowledge and prior exposure to microscope slides on the phases of mitosis effect students' visual search strategies and their ability to differentiate cells that are going through any phases of mitosis. Two different sets of microscope slide views were used for this purpose; with high and low colour…

Sonmez, Duygu; Altun, Arif; Mazman, Sacide Guzin

2012-01-01

386

Age-Related Occipito-Temporal Hypoactivation during Visual Search: Relationships between mN2pc Sources and Performance  

ERIC Educational Resources Information Center

Recently, an event-related potential (ERP) study (Lorenzo-Lopez et al., 2008) provided evidence that normal aging significantly delays and attenuates the electrophysiological correlate of the allocation of visuospatial attention (N2pc component) during a feature-detection visual search task. To further explore the effects of normal aging on the…

Lorenzo-Lopez, L.; Gutierrez, R.; Moratti, S.; Maestu, F.; Cadaveira, F.; Amenedo, E.

2011-01-01

387

Search and retrieval of plasma wave forms: Structural pattern recognition approach  

NASA Astrophysics Data System (ADS)

Databases for fusion experiments are designed to store several million wave forms. Temporal evolution signals show the same patterns under the same plasma conditions and, therefore, pattern recognition techniques can allow identification of similar plasma behaviors. Further developments in this area must be focused on four aspects: large databases, feature extraction, similarity function, and search/retrieval efficiency. This article describes an approach for pattern searching within wave forms. The technique is performed in three stages. Firstly, the signals are filtered. Secondly, signals are encoded according to a discrete set of values (code alphabet). Finally, pattern recognition is carried out via string comparisons. The definition of code alphabets enables the description of wave forms as strings, instead of representing the signals in terms of multidimensional data vectors. An alphabet of just five letters can be enough to describe any signal. In this way, signals can be stored as a sequence of characters in a relational database, thereby allowing the use of powerful structured query languages to search for patterns and also ensuring quick data access.

Dormido-Canto, S.; Farias, G.; Vega, J.; Dormido, R.; Sánchez, J.; Duro, N.; Santos, M.; Martin, J. A.; Pajares, G.

2006-10-01

388

The effects of circadian phase, time awake, and imposed sleep restriction on performing complex visual tasks: evidence from comparative visual search.  

PubMed

Cognitive performance not only differs between individuals, but also varies within them, influenced by factors that include sleep-wakefulness and biological time of day (circadian phase). Previous studies have shown that both factors influence accuracy rather than the speed of performing a visual search task, which can be hazardous in safety-critical tasks such as air-traffic control or baggage screening. However, prior investigations used simple, brief search tasks requiring little use of working memory. In order to study the effects of circadian phase, time awake, and chronic sleep restriction on the more realistic scenario of longer tasks requiring the sustained interaction of visual working memory and attentional control, the present study employed two comparative visual search tasks. In these tasks, participants had to detect a mismatch between two otherwise identical object distributions, with one of the tasks (mirror task) requiring an additional mental image transformation. Time awake and circadian phase both had significant influences on the speed, but not the accuracy of task performance. Over the course of three weeks of chronic sleep restriction, speed but not accuracy of task performance was impacted. The results suggest measures for safer performance of important tasks and point out the importance of minimizing the impact of circadian phase and sleep-wake history in laboratory vision experiments. PMID:22836655

Pomplun, Marc; Silva, Edward J; Ronda, Joseph M; Cain, Sean W; Münch, Mirjam Y; Czeisler, Charles A; Duffy, Jeanne F

2012-01-01

389

The role of pattern recognition in creative problem solving: a case study in search of new mathematics for biology.  

PubMed

Rosen classified sciences into two categories: formalizable and unformalizable. Whereas formalizable sciences expressed in terms of mathematical theories were highly valued by Rutherford, Hutchins pointed out that unformalizable parts of soft sciences are of genuine interest and importance. Attempts to build mathematical theories for biology in the past century was met with modest and sporadic successes, and only in simple systems. In this article, a qualitative model of humans' high creativity is presented as a starting point to consider whether the gap between soft and hard sciences is bridgeable. Simonton's chance-configuration theory, which mimics the process of evolution, was modified and improved. By treating problem solving as a process of pattern recognition, the known dichotomy of visual thinking vs. verbal thinking can be recast in terms of analog pattern recognition (non-algorithmic process) and digital pattern recognition (algorithmic process), respectively. Additional concepts commonly encountered in computer science, operations research and artificial intelligence were also invoked: heuristic searching, parallel and sequential processing. The refurbished chance-configuration model is now capable of explaining several long-standing puzzles in human cognition: a) why novel discoveries often came without prior warning, b) why some creators had no ideas about the source of inspiration even after the fact, c) why some creators were consistently luckier than others, and, last but not least, d) why it was so difficult to explain what intuition, inspiration, insight, hunch, serendipity, etc. are all about. The predictive power of the present model was tested by means of resolving Zeno's paradox of Achilles and the Tortoise after one deliberately invoked visual thinking. Additional evidence of its predictive power must await future large-scale field studies. The analysis was further generalized to constructions of scientific theories in general. This approach is in line with Campbell's evolutionary epistemology. Instead of treating science as immutable Natural Laws, which already existed and which were just waiting to be discovered, scientific theories are regarded as humans' mental constructs, which must be invented to reconcile with observed natural phenomena. In this way, the pursuit of science is shifted from diligent and systematic (or random) searching for existing Natural Laws to firing up humans' imagination to comprehend Nature's behavioral pattern. The insights gained in understanding human creativity indicated that new mathematics that is capable of handling effectively parallel processing and human subjectivity is sorely needed. The past classification of formalizability vs. non-formalizability was made in reference to contemporary mathematics. Rosen's conclusion did not preclude future inventions of new biology-friendly mathematics. PMID:23597605

Hong, Felix T

2013-09-01

390

When do asymmetrical full-field pattern reversal visual evoked potentials indicate visual pathway dysfunction in children?  

PubMed

Our study aimed to find out the association between full-field pattern reversal visual evoked potential (pVEP) transoccipital asymmetries and half-field pVEP transoccipital distributions in children. Over a six-month period, 46 patients (mean age: 9 years 9 months) had both monocular full-field and half-field pVEPs to test checks subtending 50 min of arc in a 35 degree full-field and 0-17.5 degree lateral half-field. Silver-silver chloride electrodes placed at Oz, O1 and O2 were referred to Fz. Monocular full-field data were categorised according to the degree of transoccipital asymmetry. Half-field data were measured and summated to see whether they explained any full-field asymmetry. In this cohort of 46 patients, eight (17%) patients had symmetrically distributed monocular full-field pVEPs for each eye. Four of these patients had normal half-field pVEP distributions for each eye, but the other four showed a half-field deficit in one or both eyes. Of the 38 patients with asymmetrically distributed full-field pVEPs in at least one eye, 17 (44%) patients showed a half-field deficit, 20 (53%) showed responsive, but symmetrically distributed half-field responses, and one patient (3%) showed typical half-field distributions. Half-field pVEPs can help explain full-field asymmetries and should be attempted in any child able to co-operate with testing and in whom visual pathway dysfunction is suspected. PMID:21046194

Mellow, Tessa B; Liasis, Alki; Lyons, Ruth; Thompson, Dorothy

2011-02-01

391

TMS of the right angular gyrus modulates priming of pop-out in visual search: combined TMS-ERP evidence.  

PubMed

During priming of pop-out, performance at discriminating a pop-out feature target in visual search is affected by whether the target on the previous trial was defined by the same feature as on the upcoming trial. Recent studies suggest that priming of pop-out relies on attentional processes. With the use of simultaneous, combined transcranial magnetic stimulation and event-related potential recording (TMS-ERP), we tested for any critical role of the right angular gyrus (rANG) and left and right frontal eye fields (FEFs)-key attentional sites-in modulating both performance and the ERPs evoked by such visual events. Intertrial TMS trains were applied while participants discriminated the orientation of a color pop-out element in a visual search array. rANG TMS disrupted priming of pop-out, reducing reaction time costs on switch trials and speeding responses when the color of the pop-out target switched. rANG TMS caused a negativity in the ERP elicited in response to the visual stimulus array, starting 210 ms after stimulus onset. Both behavioral and ERP effects were apparent only after rANG TMS, on switch trials, and when the target in the visual search array was presented in the left visual field, with no effects after left or right FEF TMS. These results provide evidence for an attentional reorienting mechanism, which originates in the rANG and is modulated by the implicit memory of the previous trial. The rANG plays a causal role on switch trials during priming of pop-out by interacting with visual processing, particularly in the ipsilateral hemisphere representing the contralateral hemifield. PMID:21880940

Taylor, Paul C J; Muggleton, Neil G; Kalla, Roger; Walsh, Vincent; Eimer, Martin

2011-12-01

392

Comparison of visually evoked local field potentials in isolated turtle brain: patterned versus blank stimulation.  

PubMed

Isolated turtle brain/eye preparation has recently been used as a bloodless animal model for detecting the magnetic resonance imaging (MRI) signal changes produced by visually evoked neuronal currents. The present work aims to determine whether checkerboard-patterned or full field flash (blank) stimulation should be used in order to achieve stronger neuronal responses in turtle brain/eye preparation. The knowledge gained in this study is essential for optimizing the visual stimulation methods in functional neuroimaging studies using turtle brain/eye preparation. In this study, visually evoked local field potentials (LFPs) were measured and compared in turtle visual cortex and optic tectum elicited by checkerboard and full field flash stimuli with three different inter-stimulus intervals (ISIs=5, 10, and 16s). It was found that the behavior of neuronal adaptation in the cortical and tectal LFP signals for checkerboard stimulation was comparable to flash stimulation. In addition, there was no significant difference in the LFP peak amplitudes (ISI=16s) between these two stimuli. These results indicate that the intensity of neuronal responses to checkerboard is comparable to flash stimulation. These two stimulation methods should be equivalent in functional neuroimaging studies using turtle brain/eye preparation. PMID:20034520

Luo, Qingfei; Lu, Huo; Lu, Hanbing; Yang, Yihong; Gao, Jia-Hong

2010-03-15

393

Representations of facial identity information in the ventral visual stream investigated with multivoxel pattern analyses.  

PubMed

The neural basis of face recognition has been investigated extensively. Using fMRI, several regions have been identified in the human ventral visual stream that seem to be involved in processing and identifying faces, but the nature of the face representations in these regions is not well known. In particular, multivoxel pattern analyses have revealed distributed maps within these regions, but did not reveal the organizing principles of these maps. Here we isolated different types of perceptual and conceptual face properties to determine which properties are mapped in which regions. A set of faces was created with systematic manipulations of featural and configural visual characteristics. In a second part of the study, personal and spatial context information was added to all faces except one. The perceptual properties of faces were represented in face regions and in other regions of interest such as early visual and object-selective cortex. Only representations in early visual cortex were correlated with pixel-based similarities between the stimuli. The representation of nonperceptual properties was less distributed. In particular, the spatial location associated with a face was only represented in the parahippocampal place area. These findings demonstrate a relatively distributed representation of perceptual and conceptual face properties that involves both face-selective/sensitive and non-face-selective cortical regions. PMID:23658192

Goesaert, Elfi; Op de Beeck, Hans P

2013-05-01

394

A reference web architecture and patterns for real-time visual analytics on large streaming data  

NASA Astrophysics Data System (ADS)

Monitoring and analysis of streaming data, such as social media, sensors, and news feeds, has become increasingly important for business and government. The volume and velocity of incoming data are key challenges. To effectively support monitoring and analysis, statistical and visual analytics techniques need to be seamlessly integrated; analytic techniques for a variety of data types (e.g., text, numerical) and scope (e.g., incremental, rolling-window, global) must be properly accommodated; interaction, collaboration, and coordination among several visualizations must be supported in an efficient manner; and the system should support the use of different analytics techniques in a pluggable manner. Especially in web-based environments, these requirements pose restrictions on the basic visual analytics architecture for streaming data. In this paper we report on our experience of building a reference web architecture for real-time visual analytics of streaming data, identify and discuss architectural patterns that address these challenges, and report on applying the reference architecture for real-time Twitter monitoring and analysis.

Kandogan, Eser; Soroker, Danny; Rohall, Steven; Bak, Peter; van Ham, Frank; Lu, Jie; Ship, Harold-Jeffrey; Wang, Chun-Fu; Lai, Jennifer

2013-12-01

395

Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects  

Microsoft Academic Search

PurposeTo evaluate the clinical use of a test battery of short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), and pattern electroretinography (PERG) in predicting progressive glaucomatous visual field defects on standard automated perimetry (SAP).

Andreas U Bayer; Carl Erb

2002-01-01

396

‘Meaningful’ Patterns in Visual Noise: Effects of Lateral Stimulation and the Observer’s Belief in ESP  

Microsoft Academic Search

Visual noise subjectively contains more meaningful patterns (1) when tachistoscopically presented to the left visual field, and (2) for persons who believe in extrasensory perception (ESP). These results indicate a possible right hemisphere mediation of delusional perception and suggest some delusional component in the belief in ESP.

Peter Brugger; Marianne Regard; Theodor Landis; Norman Cook; Denise Krebs; Joseph Niederberger

1993-01-01

397

Single-unit analysis of pattern-motion selective properties in the middle temporal visual area (MT)  

Microsoft Academic Search

The middle temporal visual area (MT) in macaque extrastriate cortex is characterized by a high proportion of neurons selective for the direction of stimulus motion, and is thus thought to play an important role in motion perception. Previous studies identified a population of cells in MT that appeared capable of coding the motion of whole visual patterns independent of the

H. R. Rodman; T. D. Albright

1989-01-01

398

Children with Fetal Alcohol Syndrome and Fetal Alcohol Effects: Patterns of Performance on IQ and Visual Motor Ability.  

ERIC Educational Resources Information Center

This study explored relationships between intelligence and visual motor ability and patterns of impairment of visual motor ability in children prenatally affected by alcohol. Fourteen children (mean age 8.2 years) diagnosed with fetal alcohol syndrome (FAS) and 50 children with possible fetal alcohol effects (FAE) were assessed with the Bender…

Kopera-Frye, Karen; Zielinski, Sharon

399

Scavengers on the Move: Behavioural Changes in Foraging Search Patterns during the Annual Cycle  

PubMed Central

Background Optimal foraging theory predicts that animals will tend to maximize foraging success by optimizing search strategies. However, how organisms detect sparsely distributed food resources remains an open question. When targets are sparse and unpredictably distributed, a Lévy strategy should maximize foraging success. By contrast, when resources are abundant and regularly distributed, simple Brownian random movement should be sufficient. Although very different groups of organisms exhibit Lévy motion, the shift from a Lévy to a Brownian search strategy has been suggested to depend on internal and external factors such as sex, prey density, or environmental context. However, animal response at the individual level has received little attention. Methodology/Principal Findings We used GPS satellite-telemetry data of Egyptian vultures Neophron percnopterus to examine movement patterns at the individual level during consecutive years, with particular interest in the variations in foraging search patterns during the different periods of the annual cycle (i.e. breeding vs. non-breeding). Our results show that vultures followed a Brownian search strategy in their wintering sojourn in Africa, whereas they exhibited a more complex foraging search pattern at breeding grounds in Europe, including Lévy motion. Interestingly, our results showed that individuals shifted between search strategies within the same period of the annual cycle in successive years. Conclusions/Significance Results could be primarily explained by the different environmental conditions in which foraging activities occur. However, the high degree of behavioural flexibility exhibited during the breeding period in contrast to the non-breeding period is challenging, suggesting that not only environmental conditions explain individuals' behaviour but also individuals' cognitive abilities (e.g., memory effects) could play an important role. Our results support the growing awareness about the role of behavioural flexibility at the individual level, adding new empirical evidence about how animals in general, and particularly scavengers, solve the problem of efficiently finding food resources.

Lopez-Lopez, Pascual; Benavent-Corai, Jose; Garcia-Ripolles, Clara; Urios, Vicente

2013-01-01

400

Motion-compensated visual pattern image sequence coding for full-motion multisession videoconferencing on multimedia workstations  

Microsoft Academic Search

Motion-compensated visual pattern image sequence coding (MCVPISC) is an improved motion-compensated version of the visual pattern image sequence coding (VPISC) encoder. It is a high-performance video codec that is easily implemented in software. The MCVPISC codec is intended for real-time desktop computer applications such as multimedia delivery, local area network and point-to-point (modem) video conferencing. We describe a version of

Barry S. Barnett; Alan C. Bovik

1996-01-01

401

Assessment of prostate cancer detection with a visual-search human model observer  

NASA Astrophysics Data System (ADS)

Early staging of prostate cancer (PC) is a significant challenge, in part because of the small tumor sizes in- volved. Our long-term goal is to determine realistic diagnostic task performance benchmarks for standard PC imaging with single photon emission computed tomography (SPECT). This paper reports on a localization receiver operator characteristic (LROC) validation study comparing human and model observers. The study made use of a digital anthropomorphic phantom and one-cm tumors within the prostate and pelvic lymph nodes. Uptake values were consistent with data obtained from clinical In-111 ProstaScint scans. The SPECT simulation modeled a parallel-hole imaging geometry with medium-energy collimators. Nonuniform attenua- tion and distance-dependent detector response were accounted for both in the imaging and the ordered-subset expectation-maximization (OSEM) iterative reconstruction. The observer study made use of 2D slices extracted from reconstructed volumes. All observers were informed about the prostate and nodal locations in an image. Iteration number and the level of postreconstruction smoothing were study parameters. The results show that a visual-search (VS) model observer correlates better with the average detection performance of human observers than does a scanning channelized nonprewhitening (CNPW) model observer.

Sen, Anando; Kalantari, Faraz; Gifford, Howard C.

2014-03-01

402

Visual search and the detection of abnormal readings in graphical displays.  

PubMed

Two experiments evaluated the properties of polygon displays and bar graphs as fault indicator for systems with many parameters. A modified visual search paradigm was used to test the effectiveness of different display configurations to be check-read for the presence of abnormal ('target') readings. Whether the task was to detect the occurrence of a single abnormal (off-limits) parameter or count the number of abnormal parameters, both displays yielded response times and error rates that were independent of the total number (from 4 to 16) of displayed parameters. When the task was fault detection, the subjects performed equally well with both types of displays. When the task was counting the number of abnormalities, performance with the bar graph was independent of the number of abnormalities but performance with the polygon display was poorer overall and deteriorated with larger numbers of abnormalities. The results contradict either the proximity-compatibility hypothesis of Wickens or the traditional classification of polygons and bar graphs as typical integral and separable displays, respectively. The results are best characterized in terms of the similarity relations between and among 'target' and 'nontarget' parameters. PMID:9062063

Greaney, J; MacRae, A W

1997-02-01

403

Adaptive methods of two-scale edge detection in post-enhancement visual pattern processing  

NASA Astrophysics Data System (ADS)

Adaptive methods are defined and experimentally studied for a two-scale edge detection process that mimics human visual perception of edges and is inspired by the parvo-cellular (P) and magno-cellular (M) physiological subsystems of natural vision. This two-channel processing consists of a high spatial acuity/coarse contrast channel (P) and a coarse acuity/fine contrast (M) channel. We perform edge detection after a very strong non-linear image enhancement that uses smart Retinex image processing. Two conditions that arise from this enhancement demand adaptiveness in edge detection. These conditions are the presence of random noise further exacerbated by the enhancement process, and the equally random occurrence of dense textural visual information. We examine how to best deal with both phenomena with an automatic adaptive computation that treats both high noise and dense textures as too much information, and gracefully shifts from a smallscale to medium-scale edge pattern priorities. This shift is accomplished by using different edge-enhancement schemes that correspond with the (P) and (M) channels of the human visual system. We also examine the case of adapting to a third image condition, namely too little visual information, and automatically adjust edge detection sensitivities when sparse feature information is encountered. When this methodology is applied to a sequence of images of the same scene but with varying exposures and lighting conditions, this edge-detection process produces pattern constancy that is very useful for several imaging applications that rely on image classification in variable imaging conditions.

Rahman, Zia-ur; Jobson, Daniel J.; Woodell, Glenn A.

2008-05-01

404

Estimating the parameters of a model of visual search from ROC data: an alternate method for fitting proper ROC curves  

NASA Astrophysics Data System (ADS)

The binormal receiver operating characteristic (ROC) model often predicts an unphysical "hook" near the upperright corner (1,1) of the ROC plot. Several models for fitting proper ROC curves avoid this problem. The purpose of this work is to describe another method that involves a model of visual search that models free-response data, and to compare the search-model predicted ROC curves with those predicted by PROPROC (proper ROC) software. The highest rating rule was used to infer ROC data from FROC data. An expression for the search-model ROC likelihood function is derived, maximizing which yielded estimates of the parameters and the fitted ROC curve. The method was applied to a dual-modality 5-reader FROC data set. The relative difference between the average AUCs for the two methods was less than 1%. A linear regression of the AUCs yielded an adjusted R-squared of 0.95 indicative of strong linear correlation between the search model AUC and PROPROC AUC, although the shapes of the predicted ROC curves were qualitatively different. This study shows the feasibility of estimating parameters characterizing visual search from data acquired in a non-search paradigm.

Chakraborty, D. P.; Svahn, Tony

2011-03-01

405

The effects of action video game experience on the time course of inhibition of return and the efficiency of visual search  

Microsoft Academic Search

The ability to efficiently search the visual environment is a critical function of the visual system, and recent research has shown that experience playing action video games can influence visual selective attention. The present research examined the similarities and differences between video game players (VGPs) and non-video game players (NVGPs) in terms of the ability to inhibit attention from returning

Alan D. Castel; Jay Pratt; Emily Drummond

2005-01-01

406

Response variability of frontal eye field neurons modulates with sensory input and saccade preparation but not visual search salience.  

PubMed

Discharge rate modulation of frontal eye field (FEF) neurons has been identified with a representation of visual search salience (physical conspicuity and behavioral relevance) and saccade preparation. We tested whether salience or saccade preparation are evident in the trial-to-trial variability of discharge rate. We quantified response variability via the Fano factor in FEF neurons recorded in monkeys performing efficient and inefficient visual search tasks. Response variability declined following stimulus presentation in most neurons, but despite clear discharge rate modulation, variability did not change with target salience. Instead, we found that response variability was modulated by stimulus luminance and the number of items in the visual field independently of attentional demands. Response variability declined to a minimum before saccade initiation, and presaccadic response variability was directionally tuned. In addition, response variability was correlated with the response time of memory-guided saccades. These results indicate that the trial-by-trial response variability of FEF neurons reflects saccade preparation and the strength of sensory input, but not visual search salience or attentional allocation. PMID:22956785

Purcell, Braden A; Heitz, Richard P; Cohen, Jeremiah Y; Schall, Jeffrey D

2012-11-01

407

More target features in visual working memory leads to poorer search guidance: Evidence from contralateral delay activity  

PubMed Central

The visual-search literature has assumed that the top-down target representation used to guide search resides in visual working memory (VWM). We directly tested this assumption using contralateral delay activity (CDA) to estimate the VWM load imposed by the target representation. In Experiment 1, observers previewed four photorealistic objects and were cued to remember the two objects appearing to the left or right of central fixation; Experiment 2 was identical except that observers previewed two photorealistic objects and were cued to remember one. CDA was measured during a delay following preview offset but before onset of a four-object search array. One of the targets was always present, and observers were asked to make an eye movement to it and press a button. We found lower magnitude CDA on trials when the initial search saccade was directed to the target (strong guidance) compared to when it was not (weak guidance). This difference also tended to be larger shortly before search-display onset and was largely unaffected by VWM item-capacity limits or number of previews. Moreover, the difference between mean strong- and weak-guidance CDA was proportional to the increase in search time between mean strong-and weak-guidance trials (as measured by time-to-target and reaction-time difference scores). Contrary to most search models, our data suggest that trials resulting in the maintenance of more target features results in poor search guidance to a target. We interpret these counterintuitive findings as evidence for strong search guidance using a small set of highly discriminative target features that remain after pruning from a larger set of features, with the load imposed on VWM varying with this feature-consolidation process.

Schmidt, Joseph; MacNamara, Annmarie; Proudfit, Greg Hajcak; Zelinsky, Gregory J.

2014-01-01

408

Flow pattern visualization in a mimic anaerobic digester: experimental and computational studies.  

PubMed

Advanced non-invasive experiments like computer automated radioactive particle tracking and computed tomography along with computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have appreciable effect on the flow pattern of the digesters. PMID:16180475

Vesvikar, M S; Varma, R; Karim, K; Al-Dahhan, M

2005-01-01

409

A wire length minimization approach to ocular dominance patterns in mammalian visual cortex  

NASA Astrophysics Data System (ADS)

The primary visual area (V1) of the mammalian brain is a thin sheet of neurons. Because each neuron is dominated by either right or left eye one can treat V1 as a binary mixture of neurons. The spatial arrangement of neurons dominated by different eyes is known as the ocular dominance (OD) pattern. We propose a theory for OD patterns based on the premise that they are evolutionary adaptations to minimize the length of intra-cortical connections. Thus, the existing OD patterns are obtained by solving a wire length minimization problem. We divide all the neurons into two classes: right- and left-eye dominated. We find that if the number of connections of each neuron with the neurons of the same class differs from that with the other class, the segregation of neurons into monocular regions indeed reduces the wire length. The shape of the regions depends on the relative number of neurons in the two classes. If both classes are equally represented we find that the optimal OD pattern consists of alternating stripes. If one class is less numerous than the other, the optimal OD pattern consists of patches of the underrepresented (ipsilateral) eye dominated neurons surrounded by the neurons of the other class. We predict the transition from stripes to patches when the fraction of neurons dominated by the ipsilateral eye is about 40%. This prediction agrees with the data in macaque and Cebus monkeys. Our theory can be applied to other binary cortical systems.

Chklovskii, Dmitri B.; Koulakov, Alexei A.

2000-09-01

410

Localizing subprocesses of visual search by correlating local brain activation in fMRI with response time model parameters.  

PubMed

In a complex cognitive task such as overt visual search, several subprocesses interact in quick alternation, such as attentional selections (i.e., spatially constrained modulation of perception) and attentional shifts/eye movements. Since temporal resolution in fMRI is low, it is difficult to assign local brain activations to these subprocesses with traditional analysis. The present paper investigates a new approach: with the response time model STRAVIS [Müller-Plath G, Pollmann S. Determining subprocesses of visual feature search with reaction time models. Psychol Res 2003;67:80-105], a visual search process is decomposed into hypothetical cognitive subprocesses and quantitatively described by individually estimated parameters like the size of the attentional focus or the attentional dwell time. In the fMRI experiment we administered the search task, correlated the estimated model parameter values for dwell time and (reciprocal) focus size to BOLD-responses, and thereby identified putative neural networks that are jointly active in the task but differentially specialized to the subprocesses attentional selection and attentional shift. First, the methodological approach was validated by the results agreeing with the literature for predefined brain areas. Second, our findings might add to the literature by specifying several more brain areas probably belonging to the two networks. Third, compared to a more traditional data analysis (contrasts of mean BOLD responses in the factorial experimental design) the method of individually correlating model parameters to BOLD proved superior provided one accepts the theoretical assumptions underlying each of the approaches. Our results demonstrate the utility of combining mathematical modeling and fMRI to investigate the neural substrates of a complex task such as visual search. PMID:18468692

Müller-Plath, Gisela

2008-06-30

411

Strain distribution in InP grown on patterned Si: Direct visualization by cathodoluminescence wavelength imaging  

NASA Astrophysics Data System (ADS)

InP has been grown on patterned Si substrates using a low temperature metalorganic chemical vapor deposition process which insures compatibility with integrated circuit technology. Two different patterns are investigated: wet chemically etched V-grooves and SiO2-masked dry etched grooves. Reduction of feature size leads to drastic defect reduction and quantum efficiencies up to those of homoepitaxially grown InP. Strain relaxation and quantum efficiency are directly visualized by cathololuminescence wavelength imaging. On (001)-and {111}-facets of V-grooves distinct relaxation of the tensile thermally induced strain are found. Surprisingly, in the bottom of V-grooves, close to or even at the InP/Si interface, a high quantum efficiency is found with a recombination time constant typical for thick InP layers of high crystallographic quality.

Grundmann, M.; Christen, J.; Heinrichsdorff, F.; Krost, A.; Bimberg, D.

1994-02-01

412

Bilinear common spatial pattern for single-trial ERP-based rapid serial visual presentation triage  

NASA Astrophysics Data System (ADS)

Common spatial pattern (CSP) analysis is a useful tool for the feature extraction of event-related potentials (ERP). However, CSP is essentially time invariant, and thus unable to exploit the temporal information of ERP. This paper proposes a variant of CSP, namely bilinear common spatial pattern (BCSP), which is capable of accommodating both spatial and temporal information. BCSP generalizes CSP through iteratively optimizing bilinear filters. These bilinear filters constitute a spatio-temporal subspace in which the separation between two conditions is maximized. The method is unique in the sense that it is mathematically intuitive and simple, as all the bilinear filters are obtained by maximizing the power ratio as CSP does. The proposed method was evaluated on 20 subjects’ ERP data collected in rapid serial visual presentation triage experiments. The results show that BCSP achieved significantly higher average test accuracy (12.3% higher, p < 0.001).

Yu, K.; Shen, K.; Shao, S.; Ng, W. C.; Li, X.

2012-08-01

413

Direction specific error patterns during continuous tracking of the subjective visual vertical.  

PubMed

The aim of this study was to characterize the error pattern of continuously tracking the perceived earth-vertical during roll rotations from upright to right or left ear-down and from right or left ear-down to upright. We compared the tracking responses of two paradigms, which either continuously activated the otoliths organs alone (constant velocity tilt) or both the otolith organs and the semicircular canals (constant acceleration tilt). The tracking responses of the subjective visual vertical showed characteristic differences depending on starting position and tilt direction relative to gravity. The error patterns in the constant-velocity and constant-acceleration tilt paradigm were reversed. Estimations during tracking, when otolith information was continuously changing, were more precise compared to estimations following fast tilts to fixed roll tilt positions. We conclude that the central processing underlying these perceptual tracking responses requires, besides the otolith input, information from the vertical semicircular canals. PMID:14726988

Keusch, S; Hess, B J M; Jaggi-Schwarz, K

2004-04-01

414

Neural Correlates of Inter-Trial Priming and Role-Reversal in Visual Search  

PubMed Central

Studies of priming of visual perception demonstrate that observers respond more quickly to targets in a field of distractors when relevant features are repeated versus novel or role-reversed. In a recent brain imaging study by Kristjánsson et al. (2007), participants were presented with two items of one color and a single item in a different color with the task of reporting the orientation of the uniquely colored item. Consistent with previous behavioral reports, they found that observers were faster to respond when the target and distractor colors were identical to the previous trial than when they were reversed. They found reduced BOLD activity in brain areas linked with attentional control on trials where the target and distractor colors were repeated relative to reversed, which they interpreted as reflecting response suppression (decreased BOLD signal for repeated stimuli). However, since their design only compared repeated versus reversed task demands, it is logically possible that this pattern reflects increased BOLD signal for role-reversed stimuli: activity required to inhibit previously facilitated information and select previously inhibited information. We explored this possibility with a task where we contrasted the signal generated by repeated, reversed, and novel features. Our data suggest that the majority of the change in neural signal elicited by priming of pop-out reflects increased activation when selection criteria are reversed.

Rorden, Christopher; Kristjansson, Arni; Revill, Kathleen Pirog; Saevarsson, Styrmir

2011-01-01

415

Discovering Weighted Patterns in Intron Sequences Using Self-Adaptive Harmony Search and Back-Propagation Algorithms  

PubMed Central

A hybrid self-adaptive harmony search and back-propagation mining system was proposed to discover weighted patterns in human intron sequences. By testing the weights under a lazy nearest neighbor classifier, the numerical results revealed the significance of these weighted patterns. Comparing these weighted patterns with the popular intron consensus model, it is clear that the discovered weighted patterns make originally the ambiguous 5SS and 3SS header patterns more specific and concrete.

Wang, Chia-Ming; Liou, Sing-Wu

2013-01-01

416

Spatial Attention Evokes Similar Activation Patterns for Visual and Auditory Stimuli  

PubMed Central

Neuroimaging studies suggest that a fronto-parietal network is activated when we expect visual information to appear at a specific spatial location. Here we examined whether a similar network is involved for auditory stimuli. We used sparse fMRI to infer brain activation while participants performed analogous visual and auditory tasks. On some trials, participants were asked to discriminate the elevation of a peripheral target. On other trials, participants made a nonspatial judgment. We contrasted trials where the participants expected a peripheral spatial target to those where they were cued to expect a central target. Crucially, our statistical analyses were based on trials where stimuli were anticipated but not presented, allowing us to directly infer perceptual orienting independent of perceptual processing. This is the first neuroimaging study to use an orthogonal-cuing paradigm (with cues predicting azimuth and responses involving elevation discrimination). This aspect of our paradigm is important, as behavioral cueing effects in audition are classically only observed when participants are asked to make spatial judgments. We observed similar fronto-parietal activation for both vision and audition. In a second experiment that controlled for stimulus properties and task difficulty, participants made spatial and temporal discriminations about musical instruments. We found that the pattern of brain activation for spatial selection of auditory stimuli was remarkably similar to what we found in our first experiment. Collectively, these results suggest that the neural mechanisms supporting spatial attention are largely similar across both visual and auditory modalities.

Smith, David V.; Davis, Ben; Niu, Kathy; Healy, Eric W.; Bonilha, Leonardo; Fridriksson, Julius; Morgan, Paul S.; Rorden, Chris

2010-01-01

417

Response processing during visual search in normal aging: the need for more time to prevent cross talk between spatial attention and manual response selection.  

PubMed

It is still not well known whether the age-related behavioural slowing observed during visual search is due to changes in the allocation of attention, in response activation patterns, or to a combination of both. To help in clarifying it, attention-related (N2 posterior contralateral; N2pc, and N2 central contralateral; N2cc) and response-related (Motor Potential; MP, and Reafferent Potential; RAP) event-related potentials (ERPs) were obtained in healthy young and older participants executing a visual search task. Age was associated with N2pc and N2cc longer latencies, earlier MP onsets and longer MP rise times. Lower N2pc, higher MP and lower RAP amplitudes were also observed. Results suggest that older participants need more time to allocate spatial attention onto the target (N2pc) and to prevent cross talk between response selection and attention direction (N2cc), and that they are slower and need higher cortical activation when preparing and executing correctly selected responses (MP). PMID:22743592

Amenedo, Elena; Lorenzo-López, Laura; Pazo-Álvarez, Paula

2012-10-01

418