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1

Different visual search strategies in stationary and moving radial patterns.  

PubMed

This study compared visual search strategies in patterns of radially moving dots (simulating self-motion) to those used in matched stationary displays (radial patterns of lines). To control for differences in target visibility, 75% detection thresholds for deviating motion direction and line orientation, respectively, were determined as a function of eccentricity in Experiment 1. These individual thresholds were used to study saccadic parameters in Experiment 2, when subjects searched for targets in the stationary and moving patterns. Despite similarities in search performance, visual search in moving radial patterns was characterised by fewer saccades, longer initial fixation times, and shorter saccadic amplitudes after the initial saccade than during search in a matched stationary radial pattern. These results suggest that detection performance alone cannot explain saccadic search behaviour, and that different search strategies may be used in moving compared to stable environments. PMID:12705959

van Loon, E M; Hooge, I Th C; Van den Berg, A V

2003-05-01

2

A Temporal Pattern Search Algorithm for Personal History Event Visualization  

Microsoft Academic Search

We present Temporal Pattern Search (TPS), a novel algorithm for searching for temporal patterns of events in historical personal histories. The traditional method of searching for such patterns uses an automaton-based approach over a single array of events, sorted by time stamps. Instead, TPS operates on a set of arrays, where each array contains all events of the same type,

Taowei David Wang; Amol Deshpande; Ben Shneiderman

2012-01-01

3

Visualized representation of visual search patterns for a visuospatial attention test  

Microsoft Academic Search

Cancellation tests have been widely used in clinical practice and in research to evaluate visuospatial attention, visual scanning\\u000a patterns, and neglect problems. The aim of the present work is to present a visualized interface for the visuospatial attentional\\u000a assessment system that can be employed to monitor and analyze attention performance and the search strategies used during\\u000a visuospatial processing of target

Ho-Chuan Huang; Tsui-Ying Wang

2008-01-01

4

Influencing Hydrologic Data Search Design by Visualizing Hydrologic Metadata Patterns  

NASA Astrophysics Data System (ADS)

The problem of enabling data search in massive data repositories - such as CUAHSI HIS HydroCatalog - requires allowing users to locate relevant data as fast as possible with no dead-end searches. Locating data - as a user interface problem - requires minimizing the number of choices that users have to make in order to locate data of interest (the so-called "click distance" in user interface terminology). In turn, minimizing click distance requires an understanding of the structure of repository contents and the relationship between user choices and how well they select data of interest in the repository. In visualizing the kinds and amounts of data available for a specific spatial and temporal extent, an immediate observation is that data availability varies widely based upon where and when one is looking. The choices presented to a user are derived from different facets of metadata. We show via treemap visualizations how different facets reduce the number of choices remaining, given each possible choice. This allows us to choose which options to present to the user, and can influence whether certain facets are presented first or more prominently in order to guide them toward successful data location. Further, our understanding of which data quantity metrics provide efficient user access to useful knowledge inform refinements to the design of the catalog itself. Possible data quantity metrics include the number of values observed of a variable at a specific site, the number of time series of a variable at a specific site, the quantity of values observed at a site normalized by observation time period, and the number of options present in other facets that describe the time series described by the options the user has already specified. Determining the extent to which these metrics can limit the choices a user must make to find useful information will influence how data harvested from various providers should be indexed to minimize search response time as the amount of information in the system continues to expand. Thus there is value in studying the structure of the catalog itself, as an instrument that enables scientific discovery.

Bedig, A.; Couch, A.

2011-12-01

5

Modeling the visual search patterns of mammographers as a Markov process  

NASA Astrophysics Data System (ADS)

A stochastic model, based on a Markov process, is developed for predicting visual search patterns of mammographers. Data for the model comes from tests where mammographic experts searched conventional screen film mammograms for microcalcifications. A three state model is proposed: (1) long dwells, (2) short dwells, and (3) no dwells, or periods of rapid eye movement. Steady state transition probabilities are reached within fourteen iterations.

Barrett, James R.; Dwyer, Samuel J.

1995-04-01

6

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

PubMed

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. PMID:21215762

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

2011-01-06

7

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 to Any 1900 1920 1940 1960 1980 1990 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Sort

8

Visual search: a retrospective.  

PubMed

Visual search, a vital task for humans and animals, has also become a common and important tool for studying many topics central to active vision and cognition ranging from spatial vision, attention, and oculomotor control to memory, decision making, and rewards. While visual search often seems effortless to humans, trying to recreate human visual search abilities in machines has represented an incredible challenge for computer scientists and engineers. What are the brain computations that ensure successful search? This review article draws on efforts from various subfields and discusses the mechanisms and strategies the brain uses to optimize visual search: the psychophysical evidence, their neural correlates, and if unknown, possible loci of the neural computations. Mechanisms and strategies include use of knowledge about the target, distractor, background statistical properties, location probabilities, contextual cues, scene context, rewards, target prevalence, and also the role of saliency, center-surround organization of search templates, and eye movement plans. I provide overviews of classic and contemporary theories of covert attention and eye movements during search explaining their differences and similarities. To allow the reader to anchor some of the laboratory findings to real-world tasks, the article includes interviews with three expert searchers: a radiologist, a fisherman, and a satellite image analyst. PMID:22209816

Eckstein, Miguel P

2011-12-30

9

Interrupted Visual Searches Reveal Volatile Search Memory  

ERIC Educational Resources Information Center

This study investigated memory from interrupted visual searches. Participants conducted a change detection search task on polygons overlaid on scenes. Search was interrupted by various disruptions, including unfilled delay, passive viewing of other scenes, and additional search on new displays. Results showed that performance was unaffected by…

Shen, Y. Jeremy; Jiang, Yuhong V.

2006-01-01

10

Influence of stimulus salience and attentional demands on visual search patterns in hemispatial neglect.  

PubMed

Seventy-five left and right brain-damaged patients, with or without hemispatial neglect, and 40 age-matched control subjects were tested on cancellation tasks with two different visual textures modeled after Julesz (1981). In one condition ("preattentive"), target elements segregated easily from background elements and were perceived effortlessly. In the other ("attentive"), target elements did not segregate easily and could be detected only after prolonged focal scrutiny. Both controls and patients were more accurate and faster on the preattentive than attentive texture. However, only neglect patients were disproportionately impaired on the attentive texture, thus suggesting that unilateral neglect is exacerbated by the low visual salience of the stimuli and a higher engagement of focal attention. Thus, a simple bedside test may help to tell apart the level of visual information processing maximally impaired in neglect patients. PMID:9292188

Aglioti, S; Smania, N; Barbieri, C; Corbetta, M

1997-08-01

11

Perceptual Encoding Efficiency in Visual Search  

Microsoft Academic Search

The authors present 10 experiments that challenge some central assumptions of the dominant theories of visual search. Their results reveal that the complexity (or redundancy) of nontarget items is a crucial but overlooked determinant of search efficiency. The authors offer a new theoretical outline that emphasizes the importance of nontarget encoding efficiency, and they test this proposal using dot pattern

Robert Rauschenberger; Steven Yantis

2006-01-01

12

Supporting Web Search with Visualization  

NASA Astrophysics Data System (ADS)

One of the fundamental goals of Web-based support systems is to promote and support human activities on the Web. The focus of this Chapter is on the specific activities associated with Web search, with special emphasis given to the use of visualization to enhance the cognitive abilities of Web searchers. An overview of information retrieval basics, along with a focus on Web search and the behaviour of Web searchers is provided. Information visualization is introduced as a means for supporting users as they perform their primary Web search tasks. Given the challenge of visualizing the primarily textual information present in Web search, a taxonomy of the information that is available to support these tasks is given. The specific challenges of representing search information are discussed, and a survey of the current state-of-the-art in visual Web search is introduced. This Chapter concludes with our vision for the future of Web search.

Hoeber, Orland; Yang, Xue Dong

13

Evolutionary pattern search algorithms.  

National Technical Information Service (NTIS)

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...

W. E. Hart

1995-01-01

14

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

15

Visual similarity effects in categorical search.  

PubMed

We asked how visual similarity relationships affect search guidance to categorically defined targets (no visual preview). Experiment 1 used a web-based task to collect visual similarity rankings between two target categories, teddy bears and butterflies, and random-category objects, from which we created search displays in Experiment 2 having either high-similarity distractors, low-similarity distractors, or "mixed" displays with high-, medium-, and low-similarity distractors. Analysis of target-absent trials revealed faster manual responses and fewer fixated distractors on low-similarity displays compared to high-similarity displays. On mixed displays, first fixations were more frequent on high-similarity distractors (bear = 49%; butterfly = 58%) than on low-similarity distractors (bear = 9%; butterfly = 12%). Experiment 3 used the same high/low/mixed conditions, but now these conditions were created using similarity estimates from a computer vision model that ranked objects in terms of color, texture, and shape similarity. The same patterns were found, suggesting that categorical search can indeed be guided by purely visual similarity. Experiment 4 compared cases where the model and human rankings differed and when they agreed. We found that similarity effects were best predicted by cases where the two sets of rankings agreed, suggesting that both human visual similarity rankings and the computer vision model captured features important for guiding search to categorical targets. PMID:21757505

Alexander, Robert G; Zelinsky, Gregory J

2011-07-14

16

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

17

Visual search in patients with left visual hemineglect.  

PubMed

In patients with hemi-spatial neglect eye movement patterns during visual search reflect not only inattention for the contralesional hemi-field, but interacting deficits of multiple visuo-spatial and cognitive functions, even in the ipsilesional hemi-field. Evidence for these deficits is presented from the literature and from saccadic scan-path analysis during feature and conjunction search in 10 healthy subjects and in 10 patients with manifest or recovered left visual neglect due to right-hemispheric stroke. Deficits include (1) a rightward shift of spatial representation, (2) deficient spatial working memory and failure of systematic search strategies, leading to multiple re-fixations, more after frontal lesions, and (3) a reduced spotlight of attention and a deficient pop-out effect of color, more after temporo-parietal lesions. PMID:12508605

Sprenger, A; Kömpf, D; Heide, W

2002-01-01

18

Parallel Processing in Visual Search Asymmetry  

Microsoft Academic Search

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 time courses of the 2 tasks were similar and

Barbara Anne Dosher; Songmei Han; Zhong-Lin Lu

2004-01-01

19

Visual Pattern Discrimination  

Microsoft Academic Search

Visual discrimination experiments were conducted using unfamiliar displays generated by a digital computer. The displays contained two side-by-side fields with different statistical, topological or heuristic properties. Discrimination was defined as that spontaneous visual process which gives the immediate impression of two distinct fields. The condition for such discrimination was found to be based primarily on clusters or lines formed by

B. Julesz

1962-01-01

20

Beyond the Search Surface: Visual Search and Attentional Engagement  

Microsoft Academic Search

Treisman (1991) described a series of visual search studies testing feature integration theory against an alternative (Duncan & Humphreys, 1989) in which feature and conjunction search are basically similar. Here the latter account is noted to have 2 distinct levels: (a) a summary of search findings in terms of stimulus similarities, and (b) a theory of how visual attention is

John Duncan; Glyn Humphreys

1992-01-01

21

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

22

Visually searching the web for structural content  

Microsoft Academic Search

Searching the information is one of the daily activities in our living, where the web is the most common information repository. Effective and efficient search on the web is a key challenge. In this paper we propose a system for web search based on the visual structure (layout and colors) of web pages. Considering that interpretation of visual structures depends

Hirofumi Miyamoto; Masahito Hirakawa

2010-01-01

23

Attentive mechanisms in visual search.  

PubMed

Selective attention can be employed to a restricted region in space or to specific objects. Many properties of this attentional window or spotlight are not well understood. In the present study, we examined the question whether the putative shape of the attentional spotlight can be determined by endogenous cueing within a visual search paradigm. Participants searched for a target among distractors, which were arranged within a vertical or horizontal rectangle. The shape of this rectangle was cued endogenously in a valid or invalid way. Response times (RTs) to correct identification of target orientation were recorded. In Experiment 1, the difference between valid and invalid RTs demonstrated that cueing resulted in elongated attentional areas. This was true only for a group of experienced psychophysical participants, whereas a group of inexperienced participants were not able to use cueing in this way. In Experiment 2, the line motion illusion was used to examine the spatial properties of the attended area. The results confirmed for both experienced and inexperienced participants that attention was confined to the cued elongated area only. We present converging evidence for an attentional spotlight whose shape can be adjusted flexibly by appropriate endogenous cueing. PMID:15559109

Panagopoulos, A; Von Grünau, M W; Galera, C

2004-01-01

24

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

25

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

26

Cumulative Intertrial Inhibition in Repeated Visual Search  

ERIC Educational Resources Information Center

|In the present study the author examined visual search when the items remain visible across trials but the location of the target varies. Reaction times for inefficient search cumulatively increased with increasing numbers of repeated search trials, suggesting that inhibition for distractors carried over successive trials. This intertrial…

Takeda, Yuji

2007-01-01

27

Age Matching Patterns and Search  

Microsoft Academic Search

Consider a marriage market with continuous-time two-sided search and trans- ferable utility in which the match payo depends on age. This paper characterizes a set of payo functions consistent with two salient marriage age patterns: (1) assortative match- ing by age, and (2) \\\\dierential age matching\\

Anja Sautmann

2011-01-01

28

Frontal-Occipital Connectivity During Visual Search  

PubMed Central

Abstract Although expectation- and attention-related interactions between ventral and medial prefrontal cortex and stimulus category-selective visual regions have been identified during visual detection and discrimination, it is not known if similar neural mechanisms apply to other tasks such as visual search. The current work tested the hypothesis that high-level frontal regions, previously implicated in expectation and visual imagery of object categories, interact with visual regions associated with object recognition during visual search. Using functional magnetic resonance imaging, subjects searched for a specific object that varied in size and location within a complex natural scene. A model-free, spatial-independent component analysis isolated multiple task-related components, one of which included visual cortex, as well as a cluster within ventromedial prefrontal cortex (vmPFC), consistent with the engagement of both top-down and bottom-up processes. Analyses of psychophysiological interactions showed increased functional connectivity between vmPFC and object-sensitive lateral occipital cortex (LOC), and results from dynamic causal modeling and Bayesian Model Selection suggested bidirectional connections between vmPFC and LOC that were positively modulated by the task. Using image-guided diffusion-tensor imaging, functionally seeded, probabilistic white-matter tracts between vmPFC and LOC, which presumably underlie this effective interconnectivity, were also observed. These connectivity findings extend previous models of visual search processes to include specific frontal–occipital neuronal interactions during a natural and complex search task.

Pantazatos, Spiro P.; Yanagihara, Ted K.; Zhang, Xian; Meitzler, Thomas

2012-01-01

29

Abrupt visual onsets and selective attention: Evidence from visual search  

Microsoft Academic Search

Examined the effect of temporal discontinuity on visual search in 3 studies with 57 college students with normal uncorrected vision. Ss were presented with a display in which 1 item had an abrupt onset, while other items were introduced by gradually removing line segments that camouflaged them. It was hypothesized that an abrupt onset in a visual display would capture

Steven Yantis; John Jonides

1984-01-01

30

Visual search engine for product images  

NASA Astrophysics Data System (ADS)

Nowadays there are many product comparison web sites. But most of them only use text information. This paper introduces a novel visual search engine for product images, which provides a brand-new way of visually locating products through Content-based Image Retrieval (CBIR) technology. We discusses the unique technical challenges, solutions, and experimental results in the design and implementation of this system.

Lin, Xiaofan; Gokturk, Burak; Sumengen, Baris; Vu, Diem

2008-01-01

31

Effects of Peripheral Visual Field Loss on Eye Movements During Visual Search  

PubMed Central

Natural vision involves sequential eye movements that bring the fovea to locations selected by peripheral vision. How peripheral visual field loss (PVFL) affects this process is not well understood. We examine how the location and extent of PVFL affects eye movement behavior in a naturalistic visual search task. Ten patients with PVFL and 13 normally sighted subjects with full visual fields (FVF) completed 30 visual searches monocularly. Subjects located a 4°?×?4° target, pseudo-randomly selected within a 26°?×?11° natural image. Eye positions were recorded at 50?Hz. Search duration, fixation duration, saccade size, and number of saccades per trial were not significantly different between PVFL and FVF groups (p?>?0.1). A ?2 test showed that the distributions of saccade directions for PVFL and FVL subjects were significantly different in 8 out of 10 cases (p?Visual Field pattern deviations for each subject were compared with the spatial distribution of eye movement directions. There were no significant correlations between saccade directional bias and visual field sensitivity across the 10 patients. Visual search performance was not significantly affected by PVFL. An analysis of eye movement directions revealed patients with PVFL show a biased directional distribution that was not directly related to the locus of vision loss, challenging feed-forward models of eye movement control. Consequently, many patients do not optimally compensate for visual field loss during visual search.

Wiecek, Emily; Pasquale, Louis R.; Fiser, Jozsef; Dakin, Steven; Bex, Peter J.

2012-01-01

32

Functional brain organization for visual search in ASD.  

PubMed

Although previous studies have shown that individuals with autism spectrum disorder (ASD) excel at visual search, underlying neural mechanisms remain unknown. This study investigated the neurofunctional correlates of visual search in children with ASD and matched typically developing (TD) children, using an event-related functional magnetic resonance imaging design. We used a visual search paradigm, manipulating search difficulty by varying set size (6, 12, or 24 items), distractor composition (heterogeneous or homogeneous) and target presence to identify brain regions associated with efficient and inefficient search. While the ASD group did not evidence accelerated response time (RT) compared with the TD group, they did demonstrate increased search efficiency, as measured by RT by set size slopes. Activation patterns also showed differences between ASD group, which recruited a network including frontal, parietal, and occipital cortices, and the TD group, which showed less extensive activation mostly limited to occipito-temporal regions. Direct comparisons (for both homogeneous and heterogeneous search conditions) revealed greater activation in occipital and frontoparietal regions in ASD than in TD participants. These results suggest that search efficiency in ASD may be related to enhanced discrimination (reflected in occipital activation) and increased top-down modulation of visual attention (associated with frontoparietal activation). PMID:18954479

Keehn, Brandon; Brenner, Laurie; Palmer, Erica; Lincoln, Alan J; Müller, Ralph-Axel

2008-11-01

33

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

34

An Interactive Visual Language for Spatiotemporal Patterns  

Microsoft Academic Search

Patterns exist in many contexts and they can be considered as knowledge sources providing useful information for our decision making. However, sometimes they are not easily identifiable and may not be visible. A visual interface for helping users to recognize patterns is needed. In this paper, we present a computer-based visual language called STVL to visualize spatiotemporal patterns. An event-anchored

K. Priyantha Hewagamage; Masahito Hirakawa

2001-01-01

35

Conditional probability modulates visual search efficiency.  

PubMed

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. PMID:24146645

Cort, Bryan; Anderson, Britt

2013-10-17

36

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

37

Urban camouflage assessment through visual search and computational saliency  

NASA Astrophysics Data System (ADS)

We present a new method to derive a multiscale urban camouflage pattern from a given set of background image samples. We applied this method to design a camouflage pattern for a given (semi-arid) urban environment. We performed a human visual search experiment and a computational evaluation study to assess the effectiveness of this multiscale camouflage pattern relative to the performance of 10 other (multiscale, disruptive and monotonous) patterns that were also designed for deployment in the same operating theater. The results show that the pattern combines the overall lowest detection probability with an average mean search time. We also show that a frequency-tuned saliency metric predicts human observer performance to an appreciable extent. This computational metric can therefore be incorporated in the design process to optimize the effectiveness of camouflage patterns derived from a set of background samples.

Toet, Alexander; Hogervorst, Maarten A.

2013-04-01

38

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

39

Sources of Top-Down Control in Visual Search  

Microsoft Academic Search

Endogenous control of visual search can influence search guidance at the level of a supradimensional topographic saliency map [Wolfe, J. M. Guided Search 2.0: A revised model of visual search. Psychonomic Bulletin & Review, 1, 202–238, 1994], and modulate nonspatial mechanisms coding saliency in dimension-specific input modules [Müller, H. J., Reimann, B., & Krummenacher, J. Visual search for singleton feature

Ralph Weidner; Joseph Krummenacher; Brit Reimann; Hermann J. Müller; Gereon R. Fink

2009-01-01

40

Innate Visual Learning through Spontaneous Activity Patterns  

Microsoft Academic Search

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

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

2008-01-01

41

Functional brain organization of preparatory attentional control in visual search.  

PubMed

Looking for an object that may be present in a cluttered visual display requires an advanced specification of that object to be created and then matched against the incoming visual input. Here, fast event-related fMRI was used to identify the brain networks that are active when preparing to search for a visual target. By isolating the preparation phase of the task it has been possible to show that for an identical stimulus, different patterns of cortical activation occur depending on whether participants anticipate a 'feature' or a 'conjunction' search task. When anticipating a conjunction search task, there was more robust activation in ventral occipital areas, new activity in the transverse occipital sulci and right posterior intraparietal sulcus. In addition, preparing for either type of search activated ventral striatum and lateral cerebellum. These results suggest that when participants anticipate a demanding search task, they develop a different advanced representation of a visually identical target stimulus compared to when they anticipate a nondemanding search. PMID:23892109

Bourke, Patrick; Brown, Steven; Ngan, Elton; Liotti, Mario

2013-07-26

42

Homo economicus in visual search.  

PubMed

How do reward outcomes affect early visual performance? Previous studies found a suboptimal influence, but they ignored the non-linearity in how subjects perceived the reward outcomes. In contrast, we find that when the non-linearity is accounted for, humans behave optimally and maximize expected reward. Our subjects were asked to detect the presence of a familiar target object in a cluttered scene. They were rewarded according to their performance. We systematically varied the target frequency and the reward/penalty policy for detecting/missing the targets. We find that 1) decreasing the target frequency will decrease the detection rates, in accordance with the literature. 2) Contrary to previous studies, increasing the target detection rewards will compensate for target rarity and restore detection performance. 3) A quantitative model based on reward maximization accurately predicts human detection behavior in all target frequency and reward conditions; thus, reward schemes can be designed to obtain desired detection rates for rare targets. 4) Subjects quickly learn the optimal decision strategy; we propose a neurally plausible model that exhibits the same properties. Potential applications include designing reward schemes to improve detection of life-critical, rare targets (e.g., cancers in medical images). PMID:19271901

Navalpakkam, Vidhya; Koch, Christof; Perona, Pietro

2009-01-23

43

ResultMaps: visualization for search interfaces.  

PubMed

Hierarchical representations are common in digital repositories, yet are not always fully leveraged in their online search interfaces. This work describes ResultMaps, which use hierarchical treemap representations with query string-driven digital library search engines. We describe two lab experiments, which find that ResultsMap users yield significantly better results over a control condition on some subjective measures, and we find evidence that ResultMaps have ancillary benefits via increased understanding of some aspects of repository content. The ResultMap system and experiments contribute an understanding of the benefits--direct and indirect--of the ResultMap approach to repository search visualization. PMID:19834172

Clarkson, Edward; Desai, Krishna; Foley, James

44

Target-distractor discriminability in visual search  

Microsoft Academic Search

Previous research has demonstrated that discriminability of target and background elements has powerful effects on visual search performance. Typically, discriminability has been manipulated between blocks or subjects, allowing subjects to anticipate the discriminability in advance of each trial, and the results, therefore, have been consistent with a wide range of models. Two experiments are reported in which the number of

HAROLD PASHLER

1987-01-01

45

Visual Search of Food Nutrition Labels  

Microsoft Academic Search

Using an eye-tracking methodology, we evaluated food nutrition labels' ability to support rapid and accurate visual search for nutrition information. Participants (5 practiced label readers and 5 nonreaders) viewed 180 trials of nutrition labels on a computer, finding answers to questions (e.g., serving size). Label manipulations included several alternative line arrangements, location of the question target item, and label size.

Joseph H. Goldberg; Claudia K. Probart; Robert E. Zak

1999-01-01

46

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

47

Similarity relations in visual search predict rapid visual categorization  

PubMed Central

How do we perform rapid visual categorization?It is widely thought that categorization involves evaluating the similarity of an object to other category items, but the underlying features and similarity relations remain unknown. Here, we hypothesized that categorization performance is based on perceived similarity relations between items within and outside the category. To this end, we measured the categorization performance of human subjects on three diverse visual categories (animals, vehicles, and tools) and across three hierarchical levels (superordinate, basic, and subordinate levels among animals). For the same subjects, we measured their perceived pair-wise similarities between objects using a visual search task. Regardless of category and hierarchical level, we found that the time taken to categorize an object could be predicted using its similarity to members within and outside its category. We were able to account for several classic categorization phenomena, such as (a) the longer times required to reject category membership; (b) the longer times to categorize atypical objects; and (c) differences in performance across tasks and across hierarchical levels. These categorization times were also accounted for by a model that extracts coarse structure from an image. The striking agreement observed between categorization and visual search suggests that these two disparate tasks depend on a shared coarse object representation.

Mohan, Krithika; Arun, S. P.

2012-01-01

48

Top-down visual search in Wimmelbild  

NASA Astrophysics Data System (ADS)

Wimmelbild which means "teeming figure picture" is a popular genre of visual puzzles. Abundant masses of small figures are brought together in complex arrangements to make one scene in a Wimmelbild. It is picture hunt game. We discuss what type of computations/processes could possibly underlie the solution of the discovery of figures that are hidden due to a distractive influence of the context. One thing for sure is that the processes are unlikely to be purely bottom-up. One possibility is to re-arrange parts and see what happens. As this idea is linked to creativity, there are abundant examples of unconventional part re-organization in modern art. A second possibility is to define what to look for. That is to formulate the search as a top-down process. We address top-down visual search in Wimmelbild with the help of diffuse distance and curvature coding fields.

Bergbauer, Julia; Tari, Sibel

2013-03-01

49

Auditory versus visual learning of temporal patterns  

Microsoft Academic Search

Temporal patterns consisting of Morse code triads were presented as auditory and visual tasks. Thirty-two Ss were tested under both conditions in a balanced design. Auditory patterns were learned consistently more easily than visual ones regardless of order of presentation. The second task was learned more rapidly than the first. The results are interpreted to support an auditory short-term store.

James R. Nazzaro; Jean N. Nazzaro

1970-01-01

50

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

51

Visual search disorders beyond pure sensory failure in patients with acute homonymous visual field defects  

Microsoft Academic Search

Patients with homonymous visual field defects (HVFD) are often crucially disabled during self-guided visual exploration of their natural environment. Abnormal visual search may be related to the sensory deficit, deficient spatial orientation or compensatory eye movements. We tested the hypothesis that visual search in HVFD is purely determined by the visual–sensory deficit by comparing nine patients with HVFD due to

Björn Machner; Andreas Sprenger; Detlef Kömpf; Thurid Sander; Wolfgang Heide; Hubert Kimmig; Christoph Helmchen

2009-01-01

52

ON THE CONVERGENCE OF PATTERN SEARCH ALGORITHMS  

Microsoft Academic Search

We introduce an abstract definition of pattern search methods for solving nonlinear unconstrained optimization problems. Our definition unifies an important collection of optimization methods that neither compute nor explicitly approximate derivatives. We exploit our characterization of pattern search methods to establish a global convergence theory that does not enforce a notion of sufficient decrease. Our analysis is possible because the

VIRGINIA TORCZON

1997-01-01

53

Saliency effects across dimensions in visual search.  

PubMed

In previous work it has been shown that search for an orientation target can only be done fast, and in parallel, when the target's orientation differs sufficiently from that of neighbouring lines. Targets with an increased local orientation contrast appear as salient and are immediately detected. In the present study, the effect of saliency from other stimulus dimensions was investigated. Five subjects were asked to look for vertical lines in texture-like displays, which were presented either embedded in the local orientation flow ("non-salient" target presentation) or at an increased feature contrast ("salient" target presentation). Saliency was obtained from local differences in orientation ("within dimension" saliency) or other visual cues ("cross dimensions" saliency), such as colour, luminance, motion, and disparity. Targets displaying cross-dimensional saliency were always non-salient in the orientation domain. The results show that subjects were slower in detecting targets from non-salient than from salient presentations. The effect of saliency on visual search is not feature-specific and, in particular, is not restricted to the stimulus dimension in which target features are searched for. PMID:8351854

Nothdurft, H C

54

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

55

Cardiac and Respiratory Responses During Visual Search in Nonretarded Children and Retarded Adolescents  

ERIC Educational Resources Information Center

The relationship between physiological response patterns and mental competence was investigated by evaluating heart rate and respiratory responses during a sustained visual-search task in 29 nonretarded grade school children and 16 retarded adolescents. (Author)

Porges, Stephen W.; Humphrey, Mary M.

1977-01-01

56

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

57

Immediate structured visual search for medical images.  

PubMed

The objective of this work is a scalable, real-time visual search engine for medical images. In contrast to existing systems that retrieve images that are globally similar to a query image, we enable the user to select a query Region Of Interest (ROI) and automatically detect the corresponding regions within all returned images. This allows the returned images to be ranked on the content of the ROI, rather than the entire image. Our contribution is two-fold: (i) immediate retrieval - the data is appropriately pre-processed so that the search engine returns results in real-time for any query image and ROI; (ii) structured output - returning ROIs with a choice of ranking functions. The retrieval performance is assessed on a number of annotated queries for images from the IRMA X-ray dataset and compared to a baseline. PMID:22003711

Simonyan, Karen; Zisserman, Andrew; Criminisi, Antonio

2011-01-01

58

Reaction time distributions constrain models of visual search  

PubMed Central

Many experiments have investigated visual search for simple stimuli like colored bars or alphanumeric characters. When eye movements are not a limiting factor, these tasks tend to produce roughly linear functions relating reaction time (RT) to the number of items in the display (set size). The slopes of the RT × set size functions for different searches fall on a continuum from highly efficient (slopes near zero) to inefficient (slopes > 25-30 msec/item). Many theories of search can produce the correct pattern of mean RTs. Producing the correct RT distributions is more difficult. In order to guide future modeling, we have collected a very large data set (about 112,000 trials) on three tasks: an efficient color feature search, an inefficient search for a 2 among 5s, and an intermediate color × orientation conjunction search. The RT distributions have interesting properties. For example, target absent distributions overlap target present more than would be expected if the decision to end search were based on a simple elapsed time threshold. Other qualitative properties of the RT distributions falsify some classes of model. For example, normalized RT distributions do not change shape as set size changes as a standard self-terminating model predicts that they should.

Wolfe, Jeremy M; Palmer, Evan M; Horowitz, Todd S

2009-01-01

59

A Novel Visualization Model for Web Search Results  

Microsoft Academic Search

This paper presents an interactive visualization system, named WebSearchViz, for visualizing the Web search results and facilitating users' navigation and exploration. The metaphor in our model is the solar system with its planets and asteroids revolving around the sun. Location, color, movement, and spatial distance of objects in the visual space are used to represent the semantic relationships between a

Tien N. Nguyen; Jun Zhang

2006-01-01

60

Competition-Induced Visual Field Differences in Search  

Microsoft Academic Search

Do visual field effects point to differences in cortical rep- resentation, or do they reflect differences in the way these represen- tations are used by other brain regions? This study explored three attributes of visual search that provide strong evidence in favor of differences in use. Competition refers to the finding that visual field differences in search efficiency are larger

Jillian H. Fecteau; James T. Enns; Alan Kingstone

2000-01-01

61

Activation of phonological competitors in visual search.  

PubMed

Recently, Meyer, Belke, Telling and Humphreys (2007) reported that competitor objects with homophonous names (e.g., boy) interfere with identifying a target object (e.g., buoy) in a visual search task, suggesting that an object name's phonology becomes automatically activated even in situations in which participants do not have the intention to speak. The present study explored the generality of this finding by testing a different phonological relation (rhyming object names, e.g., cat-hat) and by varying details of the experimental procedure. Experiment 1 followed the procedure by Meyer et al. Participants were familiarized with target and competitor objects and their names at the beginning of the experiment and the picture of the target object was presented prior to the search display on each trial. In Experiment 2, the picture of the target object presented prior to the search display was replaced by its name. In Experiment 3, participants were not familiarized with target and competitor objects and their names at the beginning of the experiment. A small interference effect from phonologically related competitors was obtained in Experiments 1 and 2 but not in Experiment 3, suggesting that the way the relevant objects are introduced to participants affects the chances of observing an effect from phonologically related competitors. Implications for the information flow in the conceptual-lexical system are discussed. PMID:23584102

Görges, Frauke; Oppermann, Frank; Jescheniak, Jörg D; Schriefers, Herbert

2013-04-10

62

SELECT: A Symbol and Pattern Searching Program.  

National Technical Information Service (NTIS)

SELECT provides a very simple means of interactively searching and printing entries in an ASCII disk file which contains up to five user-selected symbols and/or patterns. 3 figures. (ERA citation 02:015636)

D. Lai

1976-01-01

63

Software design patterns for information visualization.  

PubMed

Despite a diversity of software architectures supporting information visualization, it is often difficult to identify, evaluate, and re-apply the design solutions implemented within such frameworks. One popular and effective approach for addressing such difficulties is to capture successful solutions in design patterns, abstract descriptions of interacting software components that can be customized to solve design problems within a particular context. Based upon a review of existing frameworks and our own experiences building visualization software, we present a series of design patterns for the domain of information visualization. We discuss the structure, context of use, and interrelations of patterns spanning data representation, graphics, and interaction. By representing design knowledge in a reusable form, these patterns can be used to facilitate software design, implementation, and evaluation, and improve developer education and communication. PMID:17080809

Heer, Jeffrey; Agrawala, Maneesh

64

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

65

Reward and attentional control in visual search.  

PubMed

It has long been known that the control of attention in visual search depends both on voluntary, top-down deployment according to context-specific goals, and on involuntary, stimulus-driven capture based on the physical conspicuity of perceptual objects. Recent evidence suggests that pairing target stimuli with reward can modulate the voluntary deployment of attention, but there is little evidence that reward modulates the involuntary deployment of attention to task-irrelevant distractors. We report several experiments that investigate the role of reward learning on attentional control. Each experiment involved a training phase and a test phase. In the training phase, different colors were associated with different amounts of monetary reward. In the test phase, color was not task-relevant and participants searched for a shape singleton; in most experiments no reward was delivered in the test phase. We first show that attentional capture by physically salient distractors is magnified by a previous association with reward. In subsequent experiments we demonstrate that physically inconspicuous stimuli previously associated with reward capture attention persistently during extinction--even several days after training. Furthermore, vulnerability to attentional capture by high-value stimuli is negatively correlated across individuals with working memory capacity and positively correlated with trait impulsivity. An analysis of intertrial effects reveals that value-driven attentional capture is spatially specific. Finally, when reward is delivered at test contingent on the task-relevant shape feature, recent reward history modulates value-driven attentional capture by the irrelevant color feature. The influence of learned value on attention may provide a useful model of clinical syndromes characterized by similar failures of cognitive control, including addiction, attention-deficit/hyperactivity disorder, and obesity. PMID:23437631

Yantis, Steven; Anderson, Brian A; Wampler, Emma K; Laurent, Patryk A

2012-01-01

66

Execution Patterns in Object-Oriented Visualization  

Microsoft Academic Search

Executionpatternsareanew m etaphorforvisualiz- ing execution tracesofobject-oriented program s. W e presentan execution pattern view thatletsa program m er visualize and explore a program 's execution at varied level so f abstraction. The view em ploysvisual,navigational,and analytical techniquesthataccom m odatelengthy,real- wo rl d traces.Byclassifyingrepetitivebehaviorautom at- icallyintohigh-orderexecution patterns,w edras- ticallyreducetheinform ationaprogram m erm ust assi mi late,w ithlittlelossofinsight.

Wim De Pauw; David H. Lorenz; John M. Vlissides; Mark N. Wegman

1998-01-01

67

Supporting Web Searching of Business Intelligence with Information Visualization  

Microsoft Academic Search

In this research, we proposed and validated an approach to using information visualization to augment search engines in supporting the analysis of business stakeholder information on the Web. We report in this paper findings from a preliminary evaluation comparing a visualization prototype with a traditional method of stakeholder analysis (Web browsing and searching). We found that the prototype achieved a

Wingyan Chung; Ada Leung

2007-01-01

68

Spatial Constraints on Learning in Visual Search: Modeling Contextual Cuing  

ERIC Educational Resources Information Center

|Predictive visual context facilitates visual search, a benefit termed contextual cuing (M. M. Chun & Y. Jiang, 1998). In the original task, search arrays were repeated across blocks such that the spatial configuration (context) of all of the distractors in a display predicted an embedded target location. The authors modeled existing results using…

Brady, Timothy F.; Chun, Marvin M.

2007-01-01

69

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

70

Eye Movements Reveal How Task Difficulty Moulds Visual Search  

ERIC Educational Resources Information Center

|In two experiments we investigated the relationship between eye movements and performance in visual search tasks of varying difficulty. Experiment 1 provided evidence that a single process is used for search among static and moving items. Moreover, we estimated the functional visual field (FVF) from the gaze coordinates and found that its size…

Young, Angela H.; Hulleman, Johan

2013-01-01

71

Spatial Constraints on Learning in Visual Search: Modeling Contextual Cuing  

Microsoft Academic Search

Predictive visual context facilitates visual search, a benefit termed contextual cuing (M. M. Chun & Y. Jiang, 1998). In the original task, search arrays were repeated across blocks such that the spatial configuration (context) of all of the distractors in a display predicted an embedded target location. The authors modeled existing results using a connectionist architecture and then designed new

Timothy F. Brady; Marvin M. Chun

2007-01-01

72

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

73

Global Statistical Learning in a Visual Search Task  

ERIC Educational Resources Information Center

|Locating a target in a visual search task is facilitated when the target location is repeated on successive trials. Global statistical properties also influence visual search, but have often been confounded with local regularities (i.e., target location repetition). In two experiments, target locations were not repeated for four successive…

Jones, John L.; Kaschak, Michael P.

2012-01-01

74

The Time Course of Similarity Effects in Visual Search  

ERIC Educational Resources Information Center

|It is well established that visual search becomes harder when the similarity between target and distractors is increased and the similarity between distractors is decreased. However, in models of visual search, similarity is typically treated as a static, time-invariant property of the relation between objects. Data from other perceptual tasks…

Guest, Duncan; Lamberts, Koen

2011-01-01

75

Visual Search Deficits Are Independent of Magnocellular Deficits in Dyslexia  

ERIC Educational Resources Information Center

|The aim of this study was to investigate the theory that visual magnocellular deficits seen in groups with dyslexia are linked to reading via the mechanisms of visual attention. Visual attention was measured with a serial search task and magnocellular function with a coherent motion task. A large group of children with dyslexia (n = 70) had…

Wright, Craig M.; Conlon, Elizabeth G.; Dyck, Murray

2012-01-01

76

How important is lateral masking in visual search?  

Microsoft Academic Search

Five experiments are presented, providing empirical support of the hypothesis that the sensory phenomenon of lateral masking\\u000a may explain many well-known visual search phenomena that are commonly assumed to be governed by cognitive attentional mechanisms.\\u000a Experiment I showed that when the same visual arrays are used in visual search and in lateral masking experiments, the factors\\u000a (1) number of distractors,

A. H. Wertheim; I. T. C. Hooge; K. Krikke; A. Johnson

2006-01-01

77

Visual search asymmetries in motion and optic flow fields  

Microsoft Academic Search

In visual search, items defined by a unique feature are found easily and efficiently. Search for a moving target among stationary\\u000a distractors is one such efficient search. Search for a stationary target among moving distractors is markedly more difficult.\\u000a In the experiments reported here, we confirm this finding and further show that searches for a stationary target within a\\u000a structured

Constance S. Royden; Jeremy M. Wolfe; Nicole Klempen

2001-01-01

78

A Guided Approach for Personalized Information Search and Visualization  

Microsoft Academic Search

Our earlier study (Chen, Orthner, & Sell, 2005) showed that it is possible to record the searching strategy, to search and retrieve literature information automatically, and to visualize the retrieved information through a Web interface. The objective of this study was to update the current sys- tem into a prototype of the Literature and Information Tracking System to search, retrieve

Wei-Bang Chen; Yufeng Li; Seng-Jaw Soong; Dongquan Chen

2008-01-01

79

Online search patterns: NLM CATLINE database.  

PubMed

In this article the authors present their analysis of the online search patterns within user searching sessions of the National Library of Medicine ELHILL system and examine the user search patterns on the CATLINE database. In addition to the CATLINE analysis, a comparison is made using data previously analyzed on the MEDLINE database for the same time period, thus offering an opportunity to compare the performance parameters of different databases within the same information system. Data collection covers eight weeks and includes 441,282 transactions and over 11,067 user sessions, which accounted for 1680 hours of system usage. The descriptive analysis contained in this report can assists system design activities, while the predictive power of the transaction log analysis methodology may assists the development of real-time aids. PMID:10300015

Tolle, J E; Hah, S

1985-03-01

80

Early computation of part structure: Evidence from visual search  

Microsoft Academic Search

The visual system represents object shapes in terms of intermediate-level parts. The minima rule proposes that the visual\\u000a system uses negative minima of curvature to define boundaries between parts. We used visual search to test whether part structures\\u000a consistent with the minima rule are computed preattentively—or at least, rapidly and early in visual processing. The results\\u000a of Experiments 1 and

Yaoda Xu; Manish Singh

2002-01-01

81

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

82

Visual search deficits are independent of magnocellular deficits in dyslexia.  

PubMed

The aim of this study was to investigate the theory that visual magnocellular deficits seen in groups with dyslexia are linked to reading via the mechanisms of visual attention. Visual attention was measured with a serial search task and magnocellular function with a coherent motion task. A large group of children with dyslexia (n?=?70) had slower serial search times than a control group of typical readers. However, the effect size was small (?(p)(2) ?=?0.05) indicating considerable overlap between the groups. When the dyslexia sample was split into those with or without a magnocellular deficit, there was no difference in visual search reaction time between either group and controls. The data suggest that magnocellular sensitivity and visual spatial attention weaknesses are independent of one another. They also provide more evidence of heterogeneity in response to psychophysical tasks in groups with dyslexia. Alternative explanations for poor performance on visual attention tasks are proposed along with avenues for future research. PMID:22090158

Wright, Craig M; Conlon, Elizabeth G; Dyck, Murray

2011-11-17

83

An initial search for visual overshadowing.  

PubMed

A consistent, albeit fragile, finding over the last couple of decades has been that verbalization of hard-to-verbalize stimuli, such as faces, interferes with subsequent recognition of the described target stimulus. We sought to elicit a similar phenomenon whereby visualization interferes with verbal recognition--that is, visual overshadowing. We randomly assigned participants (n?=?180) to either concrete (easy to visualize) or abstract (difficult to visualize) sentence conditions. Following presentation, participants were asked to verbalize the sentence, visualize the sentence, or work on a filler task. As predicted, visualization of an abstract verbal stimulus resulted in significantly lower recognition accuracy; unexpectedly, however, so did verbalization. The findings are discussed within the framework of fuzzy-trace theory. PMID:22502741

Harris, Kevin R; Paul, Stephen T; Adams-Price, Carolyn E

2012-04-13

84

The Serial Process in Visual Search  

ERIC Educational Resources Information Center

|The conditions for serial search are described. A multiple target search methodology (Thornton & Gilden, 2007) is used to home in on the simplest target/distractor contrast that effectively mandates a serial scheduling of attentional resources. It is found that serial search is required when (a) targets and distractors are mirror twins, and (b)…

Gilden, David L.; Thornton, Thomas L.; Marusich, Laura R.

2010-01-01

85

Investigating cue competition in contextual cuing of visual search.  

PubMed

A fundamental principle of learning is that predictive cues or signals compete with each other to gain control over behavior. Associative and propositional reasoning theories of learning provide radically different accounts of cue competition. Propositional accounts predict that under conditions that do not afford or warrant the use of higher order reasoning processes, cue competition should not be observed. We tested this prediction in 2 contextual cuing experiments, using a visual search task in which patterns of distractor elements predict the location of a target object. Blocking designs were used in which 2 sets of predictive distractors were trained in compound, with 1 set trained independently. There was no evidence of cue competition in either experiment. In fact, in Experiment 2, we found evidence for augmentation of learning. The findings are contrasted with the predictions of an error-driven associative model of contextual cuing (Brady & Chun, 2007). PMID:21895393

Beesley, T; Shanks, David R

2011-09-05

86

Dynamic topography of pattern visual evoked potentials (PVEP) in psychogenic visual loss patients  

Microsoft Academic Search

We investigated to measure the objective visual acuity using pattern visual evoked potentials (PVEP) to help the diagnosis with psychogenic visual loss (PVL) who ranged in age from 7 to 14 years old. Pattern stimuli consisted of black and white checkerboard patterns (39, 26, 15 and 9') with a visual angle of 8 degrees and a contrast level of 15%.

A. Nakamura; A. Tabuchi; E. Matsuda; W. Yamaguchi

2000-01-01

87

Visual Search Performance in the Neglect Syndrome  

Microsoft Academic Search

Patients with hemispatial neglect fail to respond to stimuli on one side of space. We assessed to what extent the complexity and number of visual stimuli on both sides determine the severity of neglect. Patients with neglect were required to find specified targets in a cluttered visual field. Two sets of stimuli were used. One set produced effortless and parallel

Mirjam Eglin; Lynn C. Robertson; Robert T. Knight

1989-01-01

88

Eye movements in iconic visual search  

Microsoft Academic Search

Visual cognition depends critically on the moment-to-moment orientation of gaze. To change the gaze to a new location in space, that location must be computed and used by the oculomotor system. One of the most common sources of information for this computation is the visual appearance of an object. A crucial question is: How is the appearance information contained in

Rajesh P. N. Rao; Gregory J. Zelinsky; Mary M. Hayhoe; Dana H. Ballard

2002-01-01

89

Visual Search in Learning Disabled and Hyperactive Boys.  

ERIC Educational Resources Information Center

|To test the suggestion that a deficit in selective attention is characteristic of learning disabled (LD) but not hyperactive (H) children, 72 students (12 LDH, 12 H, and 36 normal Ss) were timed on visual search tasks. (Author)|

McIntyre, Curtis W.; And Others

1981-01-01

90

Metacognitive Components of Visual Search in Children  

Microsoft Academic Search

Two studies examined children's increasing ability to analyze tasks in terms of the perceptual features that affect task difficulty. Of particular interest was any understanding that perceptual confusions occur during the search for an object surrounded by objects similar in shape or color to that object. In Study 1, 32 preschoolers constructed arrays intended to make the search easy or

Patricia H. Miller; Vernon F. Haynes; Michael G. Weiss

1985-01-01

91

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

92

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

93

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

94

Visual Search by Children with and without ADHD  

ERIC Educational Resources Information Center

|Objective: To summarize the literature that has employed visual search tasks to assess automatic and effortful selective visual attention in children with and without ADHD. Method: Seven studies with a combined sample of 180 children with ADHD (M age = 10.9) and 193 normally developing children (M age = 10.8) are located. Results: Using a…

Mullane, Jennifer C.; Klein, Raymond M.

2008-01-01

95

Global Image Dissimilarity in Macaque Inferotemporal Cortex Predicts Human Visual Search Efficiency  

PubMed Central

Finding a target in a visual scene can be easy or difficult depending on the nature of the distractors. Research in humans has suggested that search is more difficult the more similar the target and distractors are to each other. However, it has not yielded an objective definition of similarity. We hypothesized that visual search performance depends on similarity as determined by the degree to which two images elicit overlapping patterns of neuronal activity in visual cortex. To test this idea, we recorded from neurons in monkey inferotemporal cortex (IT) and assessed visual search performance in humans using pairs of images formed from the same local features in different global arrangements. The ability of IT neurons to discriminate between two images was strongly predictive of the ability of humans to discriminate between them during visual search, accounting overall for 90% of the variance in human performance. A simple physical measure of global similarity – the degree of overlap between the coarse footprints of a pair of images – largely explains both the neuronal and the behavioral results. To explain the relation between population activity and search behavior, we propose a model in which the efficiency of global oddball search depends on contrast-enhancing lateral interactions in high-order visual cortex.

Sripati, Arun P.; Olson, Carl R.

2010-01-01

96

Repetition priming in visual search: Episodic retrieval, not feature priming  

Microsoft Academic Search

Previous research has shown that when the targets of successive visual searches have features in common, response times are shorter. However, the nature of the representation underlying this prim- ing and how priming is affected by the task remain uncertain. In four experiments, subjects searched for an odd-sized target and reported its orientation. The color of the items was irrelevant

LIQIANG HUANG; ALEX O. HOLCOMBE; HAROLD PASHLER

2004-01-01

97

Moray revisited: High-priority affective stimuli and visual search  

Microsoft Academic Search

Previous research offers conflicting suggestions about whether “high-priority” verbal stimuli such as an individual's own name or emotionally charged words automatically grab attention and\\/or can be detected without the usual capacity limitations. Nine experiments investigated this issue, using visual search through displays of words. In speeded search tasks, the subject's own name was detected more quickly than other targets, but

Christine R. Harris; Harold E. Pashler; Pashler Coburn

2004-01-01

98

Attention capacity and task difficulty in visual search  

Microsoft Academic Search

When a visual search task is very difficult (as when a small feature difference defines the target), even detection of a unique element may be substantially slowed by increases in display set size. This has been attributed to the influence of attentional capacity limits. We examined the influence of attentional capacity limits on three kinds of search task: difficult feature

Liqiang Huang; Harold Pashler

2005-01-01

99

ROC curves predicted by a model of visual search  

Microsoft Academic Search

In imaging tasks where the observer is uncertain whether lesions are present, and where they could be present, the image is searched for lesions. In the free-response paradigm, which closely reflects this task, the observer provides data in the form of a variable number of mark-rating pairs per image. In a companion paper a statistical model of visual search has

D. P. Chakraborty

2006-01-01

100

Why Is Visual Search Superior in Autism Spectrum Disorder?  

ERIC Educational Resources Information Center

|This study investigated the possibility that enhanced memory for rejected distractor locations underlies the superior visual search skills exhibited by individuals with autism spectrum disorder (ASD). We compared the performance of 21 children with ASD and 21 age- and IQ-matched typically developing (TD) children in a standard static search task…

Joseph, Robert M.; Keehn, Brandon; Connolly, Christine; Wolfe, Jeremy M.; Horowitz, Todd S.

2009-01-01

101

Were you paying attention to where you looked? The role of executive working memory in visual search  

Microsoft Academic Search

Recent evidence has indicated that performing a working memory task that loads executive working memory leads to less efficient\\u000a visual search (Han & Kim, 2004). We explored the role that executive functioning plays in visual search by examining the pattern\\u000a of eye movements while participants performed a search task with or without a secondary executive working memory task. Results\\u000a indicate

Matthew S. Peterson; Meliss a R. Beck; Jason H. Wong

2008-01-01

102

Repetition priming in visual search: episodic retrieval, not feature priming.  

PubMed

Previous research has shown that when the targets of successive visual searches have features in common, response times are shorter. However, the nature of the representation underlying this priming and how priming is affected by the task remain uncertain. In four experiments, subjects searched for an odd-sized target and reported its orientation. The color of the items was irrelevant to the task. When target size was repeated from the previous trial, repetition of target color speeded the response. However, when target size was different from that in the previous trial, repetition of target color slowed responses, rather than speeding them. Our results suggest that these priming phenomena reflect the same automatic mechanism as the priming of pop-out reported by Maljkovic and Nakayama (1994). However, the crossover interaction between repetition of one feature and another rules out Maljkovic and Nakayama's (1994) theory of independent potentiation of distinct feature representations. Instead, we suggest that the priming pattern results from contact with an episodic memory representation of the previous trial. PMID:15078040

Huang, Liqiang; Holcombe, Alex O; Pashler, Harold

2004-01-01

103

Parallel and Serial Processes in Visual Search  

ERIC Educational Resources Information Center

|A long-standing issue in the study of how people acquire visual information centers around the scheduling and deployment of attentional resources: Is the process serial, or is it parallel? A substantial empirical effort has been dedicated to resolving this issue. However, the results remain largely inconclusive because the methodologies that have…

Thornton, Thomas L.; Gilden, David L.

2007-01-01

104

Model of visual contrast gain control and pattern masking  

Microsoft Academic Search

INTRODUCTIONWith some notable exceptions, spatial patterns are mosteasily seen against a uniform background; backgroundsthat contain spatial patterns typically raise visual thresholds.Understanding this phenomenon of pattern maskingis an important part of understanding the process ofpattern detection and pattern visibility in general.Visual masking describes a broad range of phenomenathat may be arranged in various operational or theoreticaltaxonomies. Here we deal exclusively with...

Andrew B. Watson; Joshua A. Solomon

1997-01-01

105

Target and nontarget grouping in visual search.  

PubMed

The results of Driver et al. rule out strictly element-by-element approaches to the problem of easy conjunction search. Neither can they be explained by a simple bias toward mismatching display elements, at least as it is implemented in guided search. Such a bias is the only means of within-display interaction in many current models (Sagi & Julesz, 1984; Ullman, 1984). Instead, models (Sagi & Julesz, 1984; Ullman, 1984). Instead, the results suggest that perceptual grouping brings a bias toward common fate. For nontarget groups, this fate is rejection from further consideration; for target groups, complementarily, it is selection for further processing. PMID:7885803

Duncan, J

1995-01-01

106

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

107

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

108

The Pattern Instance Notation: A simple hierarchical visual notation for the dynamic visualization and comprehension of software patterns  

Microsoft Academic Search

Design patterns are a common tool for developers and architects to understand and reason about a software system. Visualization techniques for patterns tend to be either highly theoretical in nature or based on a structural view of a system's implementation. The Pattern Instance Notation is a simple notation technique for visualizing design patterns and other abstractions of software engineering. While

Jason Mc C. Smith

2011-01-01

109

A summary statistic representation in peripheral vision explains visual search.  

PubMed

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. PMID:22523401

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

2012-04-20

110

Moray revisited: high-priority affective stimuli and visual search.  

PubMed

Previous research offers conflicting suggestions about whether "high-priority" verbal stimuli such as an individual's own name or emotionally charged words automatically grab attention and/or can be detected without the usual capacity limitations. Nine experiments investigated this issue, using visual search through displays of words. In speeded search tasks, the subject's own name was detected more quickly than other targets, but in no case were search slopes flat enough to suggest parallel search or "pop-out". Further, names were not found to be unusually potent distractors. Emotionally charged words were neither more readily detected as targets nor more potent as distractors than neutral words. A comparison of observers' accuracy in searching briefly exposed simultaneous vs. successive displays provided further evidence that search for "high-priority" word targets is subject to the same severe capacity limitations as those that are found with search for neutral words. PMID:14681002

Harris, Christine R; Pashler, Harold E; Coburn, Noriko

2004-01-01

111

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

112

Operator-centric design patterns for information visualization software  

NASA Astrophysics Data System (ADS)

Design patterns have proven to be a useful means to make the process of designing, developing, and reusing software systems more efficient. In the area of information visualization, researchers have proposed design patterns for different functional components of the visualization pipeline. Since many visualization techniques need to display derived data as well as raw data, the data transformation stage is very important in the pipeline, yet existing design patterns are, in general, not sufficient to implement these data transformation techniques. In this paper, we propose two design patterns, operatorcentric transformation and data modifier, to facilitate the design of data transformations for information visualization systems. The key idea is to use operators to describe the data derivation and introduce data modifiers to represent the derived data. We also show that many interaction techniques can be regarded as operators as defined here, thus these two design patterns could support a wide range of visualization techniques. In addition, we describe a third design pattern, modifier-based visual mapping, that can generate visual abstraction via linking data modifiers to visual attributes. We also present a framework based on these three design patterns that supports coordinated multiple views. Several examples of multivariate visualizations are discussed to show that our design patterns and framework can improve the reusability and extensibility of information visualization systems. Finally, we explain how we have ported an existing visualization tool (XmdvTool) from its old data-centric structure to a new structure based on the above design patterns and framework.

Xie, Zaixian; Guo, Zhenyu; Ward, Matthew O.; Rundensteiner, Elke A.

2010-01-01

113

Does linear separability really matter? Complex visual search is explained by simple search.  

PubMed

Visual search in real life involves complex displays with a target among multiple types of distracters, but in the laboratory, it is often tested using simple displays with identical distracters. Can complex search be understood in terms of simple searches? This link may not be straightforward if complex search has emergent properties. One such property is linear separability, whereby search is hard when a target cannot be separated from its distracters using a single linear boundary. However, evidence in favor of linear separability is based on testing stimulus configurations in an external parametric space that need not be related to their true perceptual representation. We therefore set out to assess whether linear separability influences complex search at all. Our null hypothesis was that complex search performance depends only on classical factors such as target-distracter similarity and distracter homogeneity, which we measured using simple searches. Across three experiments involving a variety of artificial and natural objects, differences between linearly separable and nonseparable searches were explained using target-distracter similarity and distracter heterogeneity. Further, simple searches accurately predicted complex search regardless of linear separability (r = 0.91). Our results show that complex search is explained by simple search, refuting the widely held belief that linear separability influences visual search. PMID:24029822

Vighneshvel, T; Arun, S P

2013-09-12

114

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

115

Attention capacity and task difficulty in visual search.  

PubMed

When a visual search task is very difficult (as when a small feature difference defines the target), even detection of a unique element may be substantially slowed by increases in display set size. This has been attributed to the influence of attentional capacity limits. We examined the influence of attentional capacity limits on three kinds of search task: difficult feature search (with a subtle featural difference), difficult conjunction search, and spatial-configuration search. In all 3 tasks, each trial contained sixteen items, divided into two eight-item sets. The two sets were presented either successively or simultaneously. Comparison of accuracy in successive versus simultaneous presentations revealed that attentional capacity limitations are present only in the case of spatial-configuration search. While the other two types of task were inefficient (as reflected in steep search slopes), no capacity limitations were evident. We conclude that the difficulty of a visual search task affects search efficiency but does not necessarily introduce attentional capacity limits. PMID:15617666

Huang, Liqiang; Pashler, Harold

2005-01-01

116

Visual Search in a Multi-Element Asynchronous Dynamic (MAD) World  

ERIC Educational Resources Information Center

In visual search tasks participants search for a target among distractors in strictly controlled displays. We show that visual search principles observed in these tasks do not necessarily apply in more ecologically valid search conditions, using dynamic and complex displays. A multi-element asynchronous dynamic (MAD) visual search was developed in…

Kunar, Melina A.; Watson, Derrick G.

2011-01-01

117

Visual Search in a Multi-Element Asynchronous Dynamic (MAD) World  

ERIC Educational Resources Information Center

|In visual search tasks participants search for a target among distractors in strictly controlled displays. We show that visual search principles observed in these tasks do not necessarily apply in more ecologically valid search conditions, using dynamic and complex displays. A multi-element asynchronous dynamic (MAD) visual search was developed…

Kunar, Melina A.; Watson, Derrick G.

2011-01-01

118

A pattern-search-based inverse method  

NASA Astrophysics Data System (ADS)

Uncertainty in model predictions is caused to a large extent by the uncertainty in model parameters, while the identification of model parameters is demanding because of the inherent heterogeneity of the aquifer. A variety of inverse methods has been proposed for parameter identification. In this paper we present a novel inverse method to constrain the model parameters (hydraulic conductivities) to the observed state data (hydraulic heads). In the method proposed we build a conditioning pattern consisting of simulated model parameters and observed flow data. The unknown parameter values are simulated by pattern searching through an ensemble of realizations rather than optimizing an objective function. The model parameters do not necessarily follow a multi-Gaussian distribution, and the nonlinear relationship between the parameter and the response is captured by the multipoint pattern matching. The algorithm is evaluated in two synthetic bimodal aquifers. The proposed method is able to reproduce the main structure of the reference fields, and the performance of the updated model in predicting flow and transport is improved compared with that of the prior model.

Zhou, Haiyan; Gómez-HernáNdez, J. Jaime; Li, Liangping

2012-03-01

119

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

120

Irrelevant objects of expertise compete with faces during visual search  

Microsoft Academic Search

Prior work suggests that nonface objects of expertise can interfere with the perception of faces when the two categories are\\u000a alternately presented, suggesting competition for shared perceptual resources. Here, we ask whether task-irrelevant distractors\\u000a from a category of expertise compete when faces are presented in a standard visual search task. Participants searched for\\u000a a target (face or sofa) in an

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

2011-01-01

121

Techniques and Tools for Local Search Landscape Visualization and Analysis  

NASA Astrophysics Data System (ADS)

Because of their high dimensionality, combinatorial optimization problems are often difficult to analyze, and the researcher’s intuition is insufficient to grasp the relevant features. In this paper we present and discuss a set of techniques for the visualization of search landscapes aimed at supporting the researcher’s intuition on the behavior of a Stochastic Local Search algorithm applied to a combinatorial optimization problem.

Mascia, Franco; Brunato, Mauro

122

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

123

Rapid Resumption of Interrupted Search Is Independent of Age-Related Improvements in Visual Search  

ERIC Educational Resources Information Center

|In this study, 7-19-year-olds performed an interrupted visual search task in two experiments. Our question was whether the tendency to respond within 500 ms after a second glimpse of a display (the "rapid resumption" effect ["Psychological Science", 16 (2005) 684-688]) would increase with age in the same way as overall search efficiency. The…

Lleras, Alejandro; Porporino, Mafalda; Burack, Jacob A.; Enns, James T.

2011-01-01

124

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

2013-07-11

125

Bumblebee visual search for multiple learned target types.  

PubMed

Visual search is well studied in human psychology, but we know comparatively little about similar capacities in non-human animals. It is sometimes assumed that animal visual search is restricted to a single target at a time. In bees, for example, this limitation has been evoked to explain flower constancy, the tendency of bees to specialise on a single flower type. Few studies, however, have investigated bee visual search for multiple target types after extended learning and controlling for prior visual experience. We trained colour-naive bumblebees (Bombus terrestris) extensively in separate discrimination tasks to recognise two rewarding colours in interspersed block training sessions. We then tested them with the two colours simultaneously in the presence of distracting colours to examine whether and how quickly they were able to switch between the target colours. We found that bees switched between visual targets quickly and often. The median time taken to switch between targets was shorter than known estimates of how long traces last in bees' working memory, suggesting that their capacity to recall more than one learned target was not restricted by working memory limitations. Following our results, we propose a model of memory and learning that integrates our findings with those of previous studies investigating flower constancy. PMID:23948481

Nityananda, Vivek; Pattrick, Jonathan G

2013-08-15

126

Continuous processing in macaque frontal cortex during visual search  

Microsoft Academic Search

A central issue in mental chronometry is whether information is transferred between processing stages such as stimulus evaluation and response preparation in a continuous or discrete manner. We tested whether partial information about a stimulus influences the response stage by recording the activity of movement-related neurons in the frontal eye field of macaque monkeys performing a conjunction visual search and

Narcisse P. Bichot; S. Chenchal Rao; Jeffrey D. Schall

2001-01-01

127

Visual search for arbitrary objects in real scenes  

PubMed Central

How efficient is visual search in real scenes? In searches for targets among arrays of randomly placed distractors, efficiency is often indexed by the slope of the reaction time (RT) × Set Size function. However, it may be impossible to define set size for real scenes. As an approximation, we hand-labeled 100 indoor scenes and used the number of labeled regions as a surrogate for set size. In Experiment 1, observers searched for named objects (a chair, bowl, etc.). With set size defined as the number of labeled regions, search was very efficient (~5 ms/item). When we controlled for a possible guessing strategy in Experiment 2, slopes increased somewhat (~15 ms/item), but they were much shallower than search for a random object among other distinctive objects outside of a scene setting (Exp. 3: ~40 ms/item). In Experiments 4–6, observers searched repeatedly through the same scene for different objects. Increased familiarity with scenes had modest effects on RTs, while repetition of target items had large effects (>500 ms). We propose that visual search in scenes is efficient because scene-specific forms of attentional guidance can eliminate most regions from the “functional set size” of items that could possibly be the target.

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

2011-01-01

128

Collinear integration affects visual search at V1.  

PubMed

Perceptual grouping plays an indispensable role in figure-ground segregation and attention distribution. For example, a column pops out if it contains element bars orthogonal to uniformly oriented element bars. Jingling and Tseng (2013) have reported that contextual grouping in a column matters to visual search behavior: When a column is grouped into a collinear (snakelike) structure, a target positioned on it became harder to detect than on other noncollinear (ladderlike) columns. How and where perceptual grouping interferes with selective attention is still largely unknown. This article contributes to this little-studied area by asking whether collinear contour integration interacts with visual search before or after binocular fusion. We first identified that the previously mentioned search impairment occurs with a distractor of five or nine elements but not one element in a 9 × 9 search display. To pinpoint the site of this effect, we presented the search display with a short collinear bar (one element) to one eye and the extending collinear bars to the other eye, such that when properly fused, the combined binocular collinear length (nine elements) exceeded the critical length. No collinear search impairment was observed, implying that collinear information before binocular fusion shaped participants' search behavior, although contour extension from the other eye after binocular fusion enhanced the effect of collinearity on attention. Our results suggest that attention interacts with perceptual grouping as early as V1. PMID:23988390

Chow, Hiu Mei; Jingling, Li; Tseng, Chia-Huei

2013-08-29

129

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

130

Behavior and neural basis of near-optimal visual search  

PubMed Central

The ability to search efficiently for a target in a cluttered environment is one of the most remarkable functions of the nervous system. This task is difficult under natural circumstances, as the reliability of sensory information can vary greatly across space and time and is typically a priori unknown to the observer. In contrast, visual-search experiments commonly use stimuli of equal and known reliability. In a target detection task, we randomly assigned high or low reliability to each item on a trial-by-trial basis. An optimal observer would weight the observations by their trial-to-trial reliability and combine them using a specific nonlinear integration rule. We found that humans were near-optimal, regardless of whether distractors were homogeneous or heterogeneous and whether reliability was manipulated through contrast or shape. We present a neural-network implementation of near-optimal visual search based on probabilistic population coding. The network matched human performance.

Ma, Wei Ji; Navalpakkam, Vidhya; Beck, Jeffrey M; van den Berg, Ronald; Pouget, Alexandre

2013-01-01

131

Impact of Simulated Central Scotomas on Visual Search in Natural Scenes  

PubMed Central

Purpose In performing search tasks, the visual system encodes information across the visual field at a resolution inversely related to eccentricity and deploys saccades to place visually interesting targets upon the fovea where resolution is highest. The serial process of fixation, punctuated by saccadic eye movements, continues until the desired target has been located. Loss of central vision restricts the ability to resolve the high spatial information of a target, interfering with this visual search process. We investigate oculomotor adaptations to central visual field loss with gaze-contingent artificial scotomas. Methods Spatial distortions were placed at random locations in 25° square natural scenes. Gaze-contingent artificial central scotomas were updated at the screen rate (75Hz) based on a 250Hz eyetracker. Eight subjects searched the natural scene for the spatial distortion and indicated its location using a mouse-controlled cursor. Results As the central scotoma size increased, the mean search time increased [F(3,28)= 5.27, p= .05] and the spatial distribution of gaze points during fixation increased significantly along the x [F(3,28)= 6.33, p= .002] and y [F(3,28)= 3.32, p= .034] axes. Oculomotor patterns of fixation duration, saccade size and saccade duration did not change significantly, regardless of scotoma size. Conclusions There is limited automatic adaptation of the oculomotor system following simulated central vision loss.

McIlreavy, Lee; Fiser, Jozsef; Bex, Peter J.

2012-01-01

132

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

2013-03-25

133

Mandatory processing of irrelevant fearful face features in visual search.  

PubMed

Faces expressing fear may attract attention in an automatic bottom-up fashion. Here we address this issue with magneto-encephalographic (MEG) recordings in subjects performing a demanding visual search combined with the presentation of irrelevant neutral or fearful faces. The impact of the faces' emotional expression on attentional selection was assessed by analyzing the N2pc component--a modulation of the event-related magnetic field response known to reflect attentional focusing in visual search. We observed that lateralized fearful faces elicited an N2pc approximately between 240 and 400 msec in ventral extrastriate cortex that was independent of the N2pc reflecting target selection in visual search. Despite their clear influence on neural processing, fearful faces did not significantly influence behavioral performance. To clarify this discrepancy, we further performed an MEG experiment in which the demands of the search task were reduced. Under those conditions, lateralized fearful faces elicited an N2pc response that was again independent of the N2pc response to the search target. Behavioral performance was, however, influenced in a significant manner, suggesting that for behavioral effects to appear, sufficient attentional resources need to be left unoccupied by the search task--a notion put forward by the perceptual load theory. Our observations are taken to indicate that irrelevant fearful faces influence attentional processing in extrastriate visual cortex in an automatic fashion and independent of other task-relevant attentional operations. However, this may not necessarily be echoed at the behavioral level as long as task-relevant selection operations exhaust attentional resources. PMID:19702468

Fenker, Daniela B; Heipertz, Dorothee; Boehler, Carsten N; Schoenfeld, Mircea A; Noesselt, Tömme; Heinze, Hans-Jochen; Duezel, Emrah; Hopf, Jens-Max

2010-12-01

134

Pinwheel stability, pattern selection and the geometry of visual space  

Microsoft Academic Search

It has been proposed that the dynamical stability of topological defects in the visual cortex reflects the Euclidean symmetry of the visual world. We analyze defect stability and pattern selection in a generalized Swift-Hohenberg model of visual cortical development symmetric under the Euclidean group E(2). Euclidean symmetry strongly influences the geometry and multistability of model solutions but does not directly

Michael Schnabel; Matthias Kaschube; Fred Wolf

2008-01-01

135

Action search by example using randomized visual vocabularies.  

PubMed

Because actions can be small video objects, it is a challenging problem to search for similar actions in crowded and dynamic scenes when a single query example is provided. We propose a fast action search method that can efficiently locate similar actions spatiotemporally. Both the query action and the video datasets are characterized by spatio-temporal interest points. Instead of using a unified visual vocabulary to index all interest points in the database, we propose randomized visual vocabularies to enable fast and robust interest point matching. To accelerate action localization, we have developed a coarse-to-fine video subvolume search scheme, which is several orders of magnitude faster than the existing spatio-temporal branch and bound search. Our experiments on cross-dataset action search show promising results when compared with the state of the arts. Additional experiments on a 5-h versatile video dataset validate the efficiency of our method, where an action search can be finished in just 37.6 s on a regular desktop machine. PMID:22955901

Yu, Gang; Yuan, Junsong; Liu, Zicheng

2012-08-30

136

Visual Processing of Contour Patterns under Conditions of Inattentional Blindness  

Microsoft Academic Search

An inattentional blindness paradigm was adapted to measure ERPs elicited by visual contour patterns that were or were not consciously perceived. In the first phase of the experiment, subjects performed an attentionally demanding task while task-irrelevant line segments formed square-shaped patterns or random configurations. After the square patterns had been presented 240 times, subjects' awareness of these patterns was assessed.

Michael A. Pitts; Antígona Martínez; Steven A. Hillyard

137

Visual Processing of Contour Patterns under Conditions of Inattentional Blindness  

Microsoft Academic Search

An inattentional blindness paradigm was adapted to measure ERPs elicited by visual contour patterns that were or were not consciously perceived. In the first phase of the experiment, subjects performed an attentionally demanding task while task-irrelevant line segments formed square-shaped patterns or random configurations. After the square patterns had been presented 240 times, subjects' awareness of these patterns was assessed.

Michael A. Pitts; Antígona Martínez; Steven A. Hillyard

2012-01-01

138

Synchronized Audio-Visual Transients Drive Efficient Visual Search for Motion-in-Depth  

PubMed Central

In natural audio-visual environments, a change in depth is usually correlated with a change in loudness. In the present study, we investigated whether correlating changes in disparity and loudness would provide a functional advantage in binding disparity and sound amplitude in a visual search paradigm. To test this hypothesis, we used a method similar to that used by van der Burg et al. to show that non-spatial transient (square-wave) modulations of loudness can drastically improve spatial visual search for a correlated luminance modulation. We used dynamic random-dot stereogram displays to produce pure disparity modulations. Target and distractors were small disparity-defined squares (either 6 or 10 in total). Each square moved back and forth in depth in front of the background plane at different phases. The target’s depth modulation was synchronized with an amplitude-modulated auditory tone. Visual and auditory modulations were always congruent (both sine-wave or square-wave). In a speeded search task, five observers were asked to identify the target as quickly as possible. Results show a significant improvement in visual search times in the square-wave condition compared to the sine condition, suggesting that transient auditory information can efficiently drive visual search in the disparity domain. In a second experiment, participants performed the same task in the absence of sound and showed a clear set-size effect in both modulation conditions. In a third experiment, we correlated the sound with a distractor instead of the target. This produced longer search times, indicating that the correlation is not easily ignored.

Zannoli, Marina; Cass, John; Mamassian, Pascal; Alais, David

2012-01-01

139

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

140

Sources of top-down control in visual search.  

PubMed

Endogenous control of visual search can influence search guidance at the level of a supradimensional topographic saliency map [Wolfe, J. M. Guided Search 2.0: A revised model of visual search. Psychonomic Bulletin & Review, 1, 202-238, 1994], and modulate nonspatial mechanisms coding saliency in dimension-specific input modules [Müller, H. J., Reimann, B., & Krummenacher, J. Visual search for singleton feature targets across dimensions: Stimulus- and expectancy-driven effects in dimensional weighting. Journal of Experimental Psychology: Human Perception and Performance, 29, 1021-1035, 2003]. The current experiment used fMRI to dissociate these mechanisms in a singleton feature search task in which the likely target dimension (color or orientation) was semantically precued and target saliency in each dimension was varied parametrically. BOLD signal increases associated with increased demands for top-down guidance were observed within the fronto-parietal attention network and in the right anterior middle frontal gyrus. Decreasing requirements for top-down control led to BOLD signal increases in medial anterior prefrontal cortex, consistent with a gating mechanism in favor of stimulus-related processing [Burgess, P. W., Dumontheil, I., & Gilbert, S. J. The gateway hypothesis of rostral prefrontal cortex (area 10) function. Trends in Cognitive Sciences, 11, 290-298, 2007]. Another network of brain areas consisting of left lateral fronto-polar cortex, the left supramarginal gyrus, and the cerebellum, as well as a bilateral network consisting of the posterior orbital gyrus, the inferior frontal gyrus, and the pre-SMA were associated with top-down dimensional (re-) orienting. These data argue in favor of distinct endogenous control systems for visuospatial and dimension-based attentional processing. Finally, cue validity modulated saliency processing in the left temporo-parietal junction (TPJ), pointing to a crucial role of the left TPJ in integrating an endogenous dimension-based attention set with bottom-up saliency signals. PMID:19199412

Weidner, Ralph; Krummenacher, Joseph; Reimann, Brit; Müller, Hermann J; Fink, Gereon R

2009-11-01

141

Macular degeneration affects eye movement behavior during visual search.  

PubMed

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. PMID:24027546

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

2013-09-03

142

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

143

Mandatory Processing of Irrelevant Fearful Face Features in Visual Search  

Microsoft Academic Search

Faces expressing fear may attract attention in an automatic bottom–up fashion. Here we address this issue with magneto-encephalographic (MEG) recordings in subjects performing a demanding visual search combined with the presentation of irrelevant neutral or fearful faces. The impact of the faces' emotional expression on attentional selection was assessed by analyzing the N2pc component—a modulation of the event-related magnetic field

Daniela B. Fenker; Dorothee Heipertz; Carsten N. Boehler; Mircea Ariel Schoenfeld; Tömme Noesselt; Hans-Jochen Heinze; Emrah Duezel; Jens-Max Hopf

2010-01-01

144

Eye movements in active visual search: A computable phenomenological model  

Microsoft Academic Search

We present a computational model and corresponding computer simulations that mimic phenomenologically the eye movement trajectories\\u000a observed in a conjunctive visual search task. The element of randomness is captured in the model through a Monte Carlo selection\\u000a of a particular eye movement based on its probability, which depends on three factors, adjusted to match to the observed saccade\\u000a amplitude distribution,

T. D. Keech; L. Resca

2010-01-01

145

The development of visual search in infants and very young children.  

PubMed

In two experiments, 90 1- to 3-year-olds were trained in a new nonverbal task to touch a video screen that displayed a unique target resembling a popular television character. The target appeared among varying numbers of distractors that resembled another familiar television character and was either a uniquely colored shape (the feature search task) or a unique color-shape combination (the conjunction search task). Each correct response triggered a sound and produced four animated objects on the screen. Irrespective of age and experimental design (between-subjects or within-subjects), children's reaction time (RT) patterns resembled those obtained from adults in corresponding search tasks: The RT slope for feature search was flat and independent of distractor number, whereas the RT slope for conjunction search increased linearly with distractor number. These results extend visual search effects found with adults to infants and very young children and suggest that the basic perceptual processes underlying visual search are qualitatively invariant over ontogeny. PMID:11786009

Gerhardstein, Peter; Rovee-Collier, Carolyn

2002-02-01

146

Reading and visual search: a developmental study in normal children.  

PubMed

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. PMID:23894627

Seassau, Magali; Bucci, Maria-Pia

2013-07-19

147

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

Microsoft Academic Search

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

Geoffrey F. Woodman; Steven J. Luck

2007-01-01

148

Divided attention and visual search for simple versus complex features  

Microsoft Academic Search

Under what search conditions does attention affect perceptual processes, resulting in capacity limitations, rather than affecting noisy decision-making processes? Does parallel or serial processing cause the capacity limitations? To address these issues, we varied stimulus complexity, set size, and whether distractors were mirror images of the target. Both target detection and localization produced similar patterns of results. Capacity limitations only

Elizabeth Thorpe Davis; Terry Shikano; Scott A. Peterson; Rachel Keyes Michel

2003-01-01

149

Chromaticity and luminance as coding dimensions in visual search.  

PubMed

Visual search times were measured as a function of chromaticity and luminance differences between a target and distractor stimuli. Results showed that mean search time increased linearly with the number of distractors if the luminance difference between target and distractors was small but was roughly constant if the luminance difference was large. Similar results were previously found for chromaticity differences. With the number of distractor stimuli held constant, the mean search time decreased with increases in the difference between target and distractors, up to some critical difference. Further increases in target-distractor difference had little effect. Results were similar for targets defined by luminance and chromaticity. There was some advantage to combining luminance differences with chromaticity differences when the target was dimmer than the distractors. Generally there was no advantage for combining a chromaticity difference with a luminance difference when the target was brighter than the distractors. PMID:1459569

Nagy, A L; Sanchez, R R

1992-10-01

150

Information-Limited Parallel Processing in Difficult Heterogeneous Covert Visual Search  

ERIC Educational Resources Information Center

|Difficult visual search is often attributed to time-limited serial attention operations, although neural computations in the early visual system are parallel. Using probabilistic search models (Dosher, Han, & Lu, 2004) and a full time-course analysis of the dynamics of covert visual search, we distinguish unlimited capacity parallel versus serial…

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

2010-01-01

151

Automated Creation of Pattern Database Search Heuristics  

Microsoft Academic Search

Pattern databases are dictionaries for heuristic estimates storing state-to-goal distances in state space abstractions. Their\\u000a effectiveness is sensitive to the selection of the underlying patterns. Especially for multiple and additive pattern databases,\\u000a the manual selection of patterns that leads to good exploration results is involved.\\u000a \\u000a For automating the selection process, greedy bin-packing has been suggested. This paper proposes genetic algorithms

Stefan Edelkamp

2006-01-01

152

Sweep Pattern Visual Evoked Potential Acuity in Children during Their Periods of Visual Development  

Microsoft Academic Search

Purpose: To study the clinical usage of sweep pattern visual evoked potential (SPVEP) acuity in children’s visual development periods and compare the amplitude-spatial frequency (A-SP) function regression method with the amplitude-logarithm of the visual angle (A-logVA) function regression method in evaluating the SPVEP acuity of children, especially those who have poor visual acuities. Methods: Twenty-six eyes of 26 amblyopic children

Lu Li; Yu Su; Chang-zheng Chen; Chao Feng; Hong-mei Zheng; Yi-qiao Xing

2011-01-01

153

Pattern visual evoked potentials in cases of ambiguous acuity loss  

Microsoft Academic Search

Thirty patients were referred to our visual evoked potential laboratory with complaints of profound acuity loss in one or both eyes. However, the objective ophthalmologic findings were normal, including pupillary reaction, and anterior segment and fundus examinations. Transient visual evoked potentials to a 2.3-c\\/deg sinusoidal grating pattern were found to be present in 26 of these 30 patients. Visual evoked

Phyllis Bobak; Priti Khanna; James Goodwin; Mitchell Brigell

1993-01-01

154

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

Microsoft Academic Search

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, the spatial layout on trial N?1

Fuminori Ono; Yuhong Jiang; Jun-ichiro Kawahara

2005-01-01

155

Neural representations of contextual guidance in visual search of real-world scenes.  

PubMed

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. PMID:23637176

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

2013-05-01

156

A computational model for task inference in visual search.  

PubMed

We develop a probabilistic framework to infer the ongoing task in visual search by revealing what the subject is looking for during a search process. Based on the level of difficulty, two types of tasks, easy and difficult, are investigated in this work, and individual models are customized for them according to their specific dynamics. We use Hidden Markov Models (HMMs) to serve as a model for the human cognitive process that is responsible for directing the center of gaze (COG) according to the task at hand during visual search and generating task-dependent eye trajectories. This generative model, then, is used to estimate the likelihood term in a Bayesian inference formulation to infer the task given the eye trajectory. In the easy task, focus of attention (FOA) often lands on targets, whereas in the difficult one, in addition to the on-target foci of attention, deployment of attention on nontarget objects happens very often. Therefore, we suggest a single-state and a multi-state HMM to serve as the cognitive process model of attention for the easy and difficult tasks, respectively. PMID:24071637

Haji-Abolhassani, Amin; Clark, James J

2013-09-26

157

Retinotopically specific reorganization of visual cortex for tactile pattern recognition.  

PubMed

Although previous studies have shown that Braille reading and other tactile discrimination tasks activate the visual cortex of blind and sighted people, it is not known whether this kind of crossmodal 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 6 years of age, and thereafter severe acuity reduction due to corneal opacification, but no evidence of visual-field loss. Functional magnetic resonance imaging 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. PMID:19361999

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

2009-04-14

158

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

159

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

160

Inefficient visual search for second-order motion.  

PubMed

Visual search rate was used to assess attentional resources required for detection of opposing motions defined either by luminance or by modulations of texture contrast, flicker, or size. Though luminance-based targets were detected quickly, search through second-order motion was slow. Control experiments ruled out stimuli visibility, complexity, eccentricity sensitivity, and attributes of the carrier as possible accounts. Results suggest separate processing of the two types of stimuli: Luminance-based motion is detected by spatiotemporal filters, whereas second-order motion is likely processed by a capacity-limited, later stage. Rate-reducing effects of increased contrast and speed mirrored previous research suggesting that effortful feature tracking may be the mechanism. PMID:11551060

Ashida, H; Seiffert, A E; Osaka, N

2001-09-01

161

Animation of orthogonal texture patterns for vector field visualization.  

PubMed

This paper introduces orthogonal vector field visualization on 2D manifolds: a representation by lines that are perpendicular to the input vector field. Line patterns are generated by line integral convolution (LIC). This visualization is combined with animation based on motion along the vector field. This decoupling of the line direction from the direction of animation allows us to choose the spatial frequencies along the direction of motion independently from the length scales along the LIC line patterns. Vision research indicates that local motion detectors are tuned to certain spatial frequencies of textures, and the above decoupling enables us to generate spatial frequencies optimized for motion perception. Furthermore, we introduce a combined visualization that employs orthogonal LIC patterns together with conventional, tangential streamline LIC patterns in order to benefit from the advantages of these two visualization approaches. In addition, a filtering process is described to achieve a consistent and temporally coherent animation of orthogonal vector field visualization. Different filter kernels and filter methods are compared and discussed in terms of visualization quality and speed. We present respective visualization algorithms for 2D planar vector fields and tangential vector fields on curved surfaces, and demonstrate that those algorithms lend themselves to efficient and interactive GPU implementations. PMID:18467751

Bachthaler, Sven; Weiskopf, Daniel

162

A new hybrid optimization method for loading pattern search  

SciTech Connect

A new hybrid optimization method in reloading pattern search is presented in this paper, which mix genetic algorithm (GA) with tabu search (TS). The method combines global search of GA and local search of TS reasonably to enhance the search ability and computational efficiency. For verification and illustration of the advantage of this method, the proposed hybrid optimization method has been applied to the reactor reloading optimization calculation of Cartesian and hexagonal geometry core. The numerical results show that the hybrid method works faster and better than GA. (authors)

Tao, Wang [Shanghai Jiao Tong University, Shanghai 200030 (China); Zhongsheng, Xie [Xi'an Jiao Tong University, Xi'an 710049 (China)

2006-07-01

163

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

164

Gene prediction by pattern recognition and homology search.  

National Technical Information Service (NTIS)

This paper presents an algorithm for combining pattern recognition-based exon prediction and database homology search in gene model construction. The goal is to use homologous genes or partial genes existing in the database as reference models while const...

Y. Xu E. C. Uberbacher

1996-01-01

165

Inhibition and anticipation in visual search: Evidence from effects of color foreknowledge on preview search  

Microsoft Academic Search

We present four experiments in which we examined the effects of color mixing andprior target color knowledge on preview search (Watson & Humphreys, 1997). The task was to detect a target letter (an N or a Z)\\u000a that appeared along with other new letters, when old distractors remained in the visual field. In some conditions, participants\\u000a were told the target’s

Jason J. Braithwaite; Glyn W. Humphreys

2003-01-01

166

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

167

Pattern ERG and glaucomatous visual field defects  

Microsoft Academic Search

In the past five years numerous reports have suggested that ganglion cell function can be tested by means of a specialized form of electroretinography, the socalled pattern electroretinogram (PERG). Because of the important potentials of a ganglion cell test for clinical use this technique has been applied by several investigators to patients with (presumed) ganglion cell dysfunction, especially glaucoma. On

T. J. T. P. Berg; F. C. C. Riemslag; G. W. G. A. Vos; H. F. E. Verduyn Lunel

1986-01-01

168

Characterizing the development of visual search expertise in pathology residents viewing whole slide images.  

PubMed

The goal of this study was to examine and characterize changes in the ways that pathology residents examine digital whole slide images as they progress through the residency training. A series of 20 digitized breast biopsy whole slide images (half benign and half malignant biopsies) were individually shown to 4 pathology residents at four points in time--at the beginning of their first, second, third, and fourth years of residency. Their task was to examine each image and select three areas that they would most want to zoom in on in order to view the diagnostic detail at higher resolution. Eye position was recorded as they scanned each whole slide image at low magnification. The data indicate that with each successive year of experience, the residents' search patterns do change. Overall, with time, it takes significantly less time to view an individual slide and decide where to zoom, significantly fewer fixations are generated overall, and there is less examination of nondiagnostic areas. Essentially, the residents' search becomes much more efficient. These findings are similar to those in radiology, and support the theory that an important aspect of the development of expertise is improved pattern recognition (taking in more information during the initial Gestalt or gist view) as well as improved allocation of attention and visual processing resources. Progression in improvements in visual search strategies was similar, but not identical, for the 4 residents. PMID:22835956

Krupinski, Elizabeth A; Graham, Anna R; Weinstein, Ronald S

2012-07-24

169

Fast search algorithms for vector quantization and pattern matching  

Microsoft Academic Search

A fundamental computational task that arises in several areas of signal processing is pattern matching, where a given test pattern is compared with a large set of stored templates, to find the best match that minimizes a given measure of dissimilarity. Three different geometrically-oriented methods are proposed for substantially reducing the computational complexity of the search process by reducing the

De-Yuan Cheng; Allen Gersho; Bhaskar Ramamurthi; Yair Shoham

1984-01-01

170

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

171

Flow pattern visualization of a simulated digester  

Microsoft Academic Search

Mixing patterns inside a simulated flat bottom digester were imaged using the non-invasive techniques of computer automated radioactive particle tracking (CARPT) and computed tomography (CT). Mixing\\/agitation was provided using gas (air) recirculation at three different flow rates (Qg) of 28.32, 56.64 and 84.96l\\/h, corresponding to superficial gas velocities of 0.025, 0.05 and 0.075cm\\/s, respectively. Better mixing was observed in the

Khursheed Karim; Rajneesh Varma; Mehul Vesvikar; M. H. Al-Dahhan

2004-01-01

172

Invisible Calibration Pattern based on Human Visual Perception  

NASA Astrophysics Data System (ADS)

In this paper, we propose an arrangement and detection method of an invisible calibration pattern based on characteristics of human visual perception. A calibration pattern is arranged around contents where invisible data is embedded, as some feature points between an original image and the scanned image for normalization of the scanned image. However, it is clear that conventional methods interfere with page layout and artwork of contents. Moreover, conventional visible patterns show a third person the position of embedded data. Therefore, visible calibration patterns are not suitable for security service. The most important part of human visual perception in the proposed method is the spectral luminous efficiency characteristic and the chromatic spatial frequency characteristic. In addition, a back ground color in surrounding of contents is not restricted to uniform color by using the proposed calibration pattern. It is suggest that the proposed method protect page layout and artwork.

Takimoto, Hironori; Yoshimori, Seiki; Mitsukura, Yasue; Fukumi, Minoru

173

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

2012-02-18

174

EXAMINING THE VIABILITY OF THE NEISSER SEARCH MODEL IN THE FLIGHT DOMAIN AND THE BENEFITS OF HIGHLIGHTING IN VISUAL SEARCH  

Microsoft Academic Search

We conducted four experiments to examine the visual search capability of pilots and examine how search times could be reduced, invoking the framework of Neisser's serial self terminating (SST) search model. In Experiment 1 which manipulated target presence and set size, our results show increases in response time as array size increases: an effect predicted by the SST model. In

Ashley Nunes; Christopher Wickens; Shanquin Yin

2006-01-01

175

Visual search characteristics in mammogram reading: SFM vs. FFDM  

NASA Astrophysics Data System (ADS)

Previous studies comparing radiologists' behavior when reading mammograms that were 'digitized' from screen-film mammography (SFM) films and 'digital' mammograms obtained through the use of Full-Field Digital Mammography (FFDM) systems either showed a significant advantage to FFDM (mostly when a double-reading strategy was used) or no difference in performance between the two modalities (primarily when a single-reader strategy was used). The visual search characteristics used by radiologists in the reading of 'digitized' mammograms have been previously studied, but few perceptual studies have been carried out to characterize radiologists' behavior when reading 'digital' mammograms. In this paper we will compare the perceptual features related to the radiologists' reading of 'digital' mammograms with those related to the reading of 'digitized' mammograms. In addition, we will use spatial frequency analysis to characterize such a behavior and compare it to the one employed in the reading of 'digitized' mammograms.

Mello-Thoms, Claudia

2010-03-01

176

On the preattentive accessibility of stereoscopic disparity: evidence from visual search.  

PubMed

We examined the generality of the claim that stereoscopic disparity is detectable in parallel across the visual field. Using a search paradigm with random-dot stereograms, we varied the relative disparity of target and distractor items. When both target and distractors had crossed disparities, both search functions (i.e., target in front of distractors and target behind distractors) were linear with positive slopes. When both target and distractors had uncrossed disparities, the pattern of results depended upon whether the target was in front of or behind the distractors-specifically, when the target was in front of the distractors, search functions were similar to those seen for "crossed" search, but when the target was behind the distractors, a nonlinear search function was found. Finally, when the target and distractors straddled the plane of fixation, a nonlinear search function was found when the target was in front of the distractors; however, when the target was behind the distractors, a linear search function with a large positive slope was found. We show that the nonlinear search functions are consistent with the effects of an intervening global surface percept. We also show that the size of the stimulus display may be a factor in some relative depth cases. Additionally, we replicate Steinman's (1987) finding that search is parallel when the distractors are located at the plane of fixation and the target disparity is crossed, eliminating monocular and spatial cues to target presence that may have been present in his original study. In a final control experiment, we showed that reaction times did not increase with set size when observers performed another kind of perceptual task on similar random-dot stereogram displays. This eliminates the possibility that some of the results obtained here can be explained by increases in the difficulty of perceiving/fusing the stimuli when the number of distractors is increased. PMID:9055616

O'Toole, A J; Walker, C L

1997-02-01

177

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

2008-06-28

178

What can visual content analysis do for text based image search?  

Microsoft Academic Search

Modern image search engines such as Google, Yahoo!, Microsoft Live image search are all text meta word based. To search for images, the users type in a text query and the search engines rank the result images almost sorely based on the text meta-words. The abundant visual information in the images themselves is largely neglected. Recently, we have observed several

Gang Hua; Qi Tian

2009-01-01

179

Extending Mashups to Visualize Patterns in Temporal Data  

Microsoft Academic Search

Many datasets are now published as streams of time- stamped, geo-encoded events using GeoRSS. To understand patterns within this class of data, we have taken ideas from mashups and extended them to develop new visual components that present live geospatial data in novel ways. The components are interactive, live, linked and contain many novel features for understanding temporal and geospatial

Stephen G. Eick; Andrew Eick; Jesse Fugitt; James E. Heath; Mark Ross

180

Search Deficits in Neglect Patients Are Dependent on Size of the Visual Scene  

Microsoft Academic Search

Patients with hemispatial neglect are impaired at moving their attention to a target on the contralesional display side. In the present study, visual display area was varied independently of the number of items displayed within the area. Patients searched for the absence of a simple visual feature in displays that produce serial search performance in normals (R. Klein, 1988; A.

Mirjam Eglin; Lynn C. Robertson; Robert T. Knight; Peter Brugger

1994-01-01

181

Toddlers with Autism Spectrum Disorder Are More Successful at Visual Search than Typically Developing Toddlers  

ERIC Educational Resources Information Center

Plaisted, O'Riordan and colleagues (Plaisted, O'Riordan & Baron-Cohen, 1998; O'Riordan, 2004) showed that school-age children and adults with Autism Spectrum Disorder (ASD) are faster at finding targets in certain types of visual search tasks than typical controls. Currently though, there is very little known about the visual search skills of very…

Kaldy, Zsuzsa; Kraper, Catherine; Carter, Alice S.; Blaser, Erik

2011-01-01

182

Analysis and modeling of fixation point selection for visual search in cluttered backgrounds  

Microsoft Academic Search

Hard-to-see targets are generally only detected by human observers once they have been fixated. Hence, understanding how the human visual system allocates fixation locations is necessary for predicting target detectability. Visual search experiments were conducted where observers searched for military vehicles in cluttered terrain. Instantaneous eye position measurements were collected using an eye tracker. The resulting data was partitioned into

Magnus Snorrason; James Hoffman; Harald Ruda

2000-01-01

183

Query suggestions for mobile search: understanding usage patterns  

Microsoft Academic Search

Entering search terms on mobile phones is a time consuming and cumbersome task. In this paper, we explore the usage patterns of query entry interfaces that display suggestions. Our primary goal is to build a usage model of query suggestions in order to provide user interface guidelines for mobile text prediction interfaces. We find that users who were asked to

Maryam Kamvar; Shumeet Baluja

2008-01-01

184

Optimal asymmetrical SVM using pattern search. A health care application.  

PubMed

This paper considers the model selection problem for Support Vector Machines. A well-known derivative Pattern Search method, which aims to tune hyperparameter values using an empirical error estimate as a steering criterion, is proposed. This approach is experimentally evaluated on a health care problem which involves discriminating nosocomially infected patients from non-infected patients. The Hooke and Jeeves Pattern Search (HJPS) method is shown to improve the results achieved by Grid Search (GS) in terms of solution quality and computational efficiency. Unlike most other parameter tuning techniques, our approach does not require supplementary effort such as computation of derivatives, making them well suited for practical purposes. This method produces encouraging results: it exhibits good performance and convergence properties. PMID:21893810

Cohen, Gilles; Meyer, Rodolphe

2011-01-01

185

Abnormality of the pattern electroretinogram and pattern visual evoked cortical response in esotropic cats  

Microsoft Academic Search

In six 3-week-old kittens, the tendon of the lateral rectus muscle of one eye was sectioned under anaesthesia in order to induce an esotropic (nasally-directed) squint. At maturity, the pattern electroretinogram (PERG) and pattern visual evoked response (PVER) were recorded under anaesthesia to phase-reversal at 1.67 Hz of a 0.5 c\\/deg square wave grating pattern of 75% contrast. Refraction was

M. L. Devlin; J. L. Jay; J. D. Morrison

1989-01-01

186

Information content of visual scenes influences systematic search of desert ants.  

PubMed

Many animals - including insects - navigate visually through their environment. Solitary foraging desert ants are known to acquire visual information from the surrounding panorama and use it to navigate along habitual routes or to pinpoint a goal such as the nest. Returning foragers that fail to find the nest entrance engage in searching behaviour, during which they continue to use vision. The characteristics of searching behaviour have typically been investigated in unfamiliar environments. Here we investigated in detail the nest-searching behaviour of Melophorus bagoti foragers within the familiar visual environment of their nest. First, by relating search behaviour to the information content of panoramic (360 deg) images, we found that searches were more accurate in visually cluttered environments. Second, as observed in unfamiliar visual surrounds, searches were dynamic and gradually expanded with time, showing that nest pinpointing is not rigidly controlled by vision. Third, contrary to searches displayed in unfamiliar environments, searches observed here could be modelled as a single exponential search strategy, which is similar to a Brownian walk, and there was no evidence of a Lévy walk. Overall, our results revealed that searching behaviour is remarkably flexible and varies according to the relevance of information provided by the surrounding visual scenery. PMID:23125338

Schultheiss, Patrick; Wystrach, Antoine; Legge, Eric L G; Cheng, Ken

2012-11-01

187

Stable individual differences in search strategy? The effect of task demands and motivational factors on scanning strategy in visual search.  

PubMed

Previous studies have demonstrated large individual differences in scanning strategy during a dynamic visual search task (E. Becic, A. F. Kramer, & W. R. Boot, 2007; W. R. Boot, A. F. Kramer, E. Becic, D. A. Wiegmann, & T. Kubose, 2006). These differences accounted for substantial variance in performance. Participants who chose to search covertly (without eye movements) excelled, participants who searched overtly (with eye movements) performed poorly. The aim of the current study was to investigate the stability of scanning strategies across different visual search tasks in an attempt to explain why a large percentage of observers might engage in maladaptive strategies. Scanning strategy was assessed for a group of observers across a variety of search tasks without feedback (efficient search, inefficient search, change detection, dynamic search). While scanning strategy was partly determined by task demands, stable individual differences emerged. Participants who searched either overtly or covertly tended to adopt the same strategy regardless of the demands of the search task, even in tasks in which such a strategy was maladaptive. However, when participants were given explicit feedback about their performance during search and performance incentives, strategies across tasks diverged. Thus it appears that observers by default will favor a particular search strategy but can modify this strategy when it is clearly maladaptive to the task. PMID:19757946

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

2009-03-13

188

Visual Working Memory Supports the Inhibition of Previously Processed Information: Evidence From Preview Search  

Microsoft Academic Search

In four experiments we assessed whether visual working memory (VWM) maintains a record of previously processed visual information, allowing old information to be inhibited, and new information to be prioritized. Specifically, we evaluated whether VWM contributes to the inhibition (i.e., visual marking) of previewed distractors in a preview search. We evaluated this proposal by testing three predictions. First, Experiments 1

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

2012-01-01

189

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

190

Bicycle accidents and drivers' visual search at left and right turns.  

PubMed

The accident data base of the City of Helsinki shows that when drivers cross a cycle path as they enter a non-signalized intersection, the clearly dominant type of car-cycle crashes is that in which a cyclist comes from the right and the driver is turning right, in marked contrast to the cases with drivers turning left (Pasanen 1992; City of Helsinki, Traffic Planning Department, Report L4). This study first tested an explanation that drivers turning right simply focus their attention on the cars coming from the left-those coming from the right posing no threat to them-and fail to see the cyclist from the right early enough. Drivers' scanning behavior was studied at two T-intersections. Two well-hidden video cameras were used, one to measure the head movements of the approaching drivers and the other one to measure speed and distance from the cycle crossroad. The results supported the hypothesis: the drivers turning right scanned the right leg of the T-intersection less frequently and later than those turning left. Thus, it appears that drivers develop a visual scanning strategy which concentrates on detection of more frequent and major dangers but ignores and may even mask visual information on less frequent dangers. The second part of the study evaluated different countermeasures, including speed humps, in terms of drivers' visual search behavior. The results suggested that speed-reducing countermeasures changed drivers' visual search patterns in favor of the cyclists coming from the right, presumably at least in part due to the fact that drivers were simply provided with more time to focus on each direction. PMID:8703272

Summala, H; Pasanen, E; Räsänen, M; Sievänen, J

1996-03-01

191

Compensatory strategies following visual search training in patients with homonymous hemianopia: an eye movement study  

Microsoft Academic Search

A total of 29 patients with homonymous visual field defects without neglect practised visual search in 20 daily sessions,\\u000a over a period of 4 weeks. Patients searched for a single randomly positioned target amongst distractors displayed for 3 s.\\u000a After training patients demonstrated significantly shorter reaction times for search stimuli (Pambakian et al. in J Neurol\\u000a Neurosurg Psychiatry 75:1443–1448, 2004). In this

Sabira K. MannanAlidz; Alidz L. M. Pambakian; Christopher Kennard

2010-01-01

192

Transformation of an uncertain video search pipeline to a sketch-based visual analytics loop.  

PubMed

Traditional sketch-based image or video search systems rely on machine learning concepts as their core technology. However, in many applications, machine learning alone is impractical since videos may not be semantically annotated sufficiently, there may be a lack of suitable training data, and the search requirements of the user may frequently change for different tasks. In this work, we develop a visual analytics systems that overcomes the shortcomings of the traditional approach. We make use of a sketch-based interface to enable users to specify search requirement in a flexible manner without depending on semantic annotation. We employ active machine learning to train different analytical models for different types of search requirements. We use visualization to facilitate knowledge discovery at the different stages of visual analytics. This includes visualizing the parameter space of the trained model, visualizing the search space to support interactive browsing, visualizing candidature search results to support rapid interaction for active learning while minimizing watching videos, and visualizing aggregated information of the search results. We demonstrate the system for searching spatiotemporal attributes from sports video to identify key instances of the team and player performance. PMID:24051777

Legg, Philip A; Chung, David H S; Parry, Matthew L; Bown, Rhodri; Jones, Mark W; Griffiths, Iwan W; Chen, Min

2013-12-01

193

Perception and Painting: A Search for Effective, Engaging Visualizations  

Microsoft Academic Search

Scientific visualization represents information as images that let us explore, discover, analyze and validate large collections of data. Much research in this area is dedicated to designing effective visualizations that support specific analysis needs. Recently, though, we've considered visualizations from another angle. We've started asking, \\

Christopher G. Healey; James T. Enns

2002-01-01

194

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

195

Autonomous visual model building based on image crawling through internet search engines  

Microsoft Academic Search

In this paper, we propose an autonomous learning scheme to automatically build visual semantic concept models from the output data of Internet search engines without any manual labeling work. First of all, images are gathered by crawling through the Internet using a search engine such as Google. Then, we model the search results as \\

Xiaodan Song; Ching-Yung Lin; Ming-Ting Sun

2004-01-01

196

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

197

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.…

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

2010-01-01

198

Visual Search Is Postponed during the Attentional Blink until the System Is Suitably Reconfigured  

ERIC Educational Resources Information Center

|J. S. Joseph, M. M. Chun, and K. Nakayama (1997) found that pop-out visual search was impaired as a function of intertarget lag in an attentional blink (AB) paradigm in which the 1st target was a letter and the 2nd target was a search display. In 4 experiments, the present authors tested the implication that search efficiency should be similarly…

Ghorashi, S. M. Shahab; Smilek, Daniel; Di Lollo, Vincent

2007-01-01

199

Perception and Painting: A Search for Effective, Engaging Visualizations ________ Visualization Viewpoints  

Microsoft Academic Search

cientific visualization represents information as images that let us explore, discover, analyze, and validate large collections of data. Much research in this area is dedicated to designing effective visualizations that support specific analysis needs. Recently, though, we've considered visualizations from another angle. We've started asking, Are visualizations beautiful? Can we consider visualizations works of art? You might expect answers to

James T. Enns; Theresa-Marie Rhyne; Lloyd Trinish

200

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

2013-03-13

201

Spontaneous pattern formation and pinning in the visual cortex  

NASA Astrophysics Data System (ADS)

Bifurcation theory and perturbation theory can be combined with a knowledge of the underlying circuitry of the visual cortex to produce an elegant story explaining the phenomenon of visual hallucinations. A key insight is the application of an important set of ideas concerning spontaneous pattern formation introduced by Turing in 1952. The basic mechanism is a diffusion driven linear instability favoring a particular wavelength that determines the size of the ensuing stripe or spot periodicity of the emerging spatial pattern. Competition between short range excitation and longer range inhibition in the connectivity profile of cortical neurons provides the difference in diffusion length scales necessary for the Turing mechanism to occur and has been proven by Ermentrout and Cowan to be sufficient to explain the generation of a subset of reported geometric hallucinations. Incorporating further details of the cortical circuitry, namely that neurons are also weakly connected to other neurons sharing a particular stimulus orientation or spatial frequency preference at even longer ranges and the resulting shift-twist symmetry of the neuronal connectivity, improves the story. We expand this approach in order to be able to include the tuned responses of cortical neurons to additional visual stimulus features such as motion, color and disparity. We apply a study of nonlinear dynamics similar to the analysis of wave propagation in a crystalline lattice to demonstrate how a spatial pattern formed through the Turing instability can be pinned to the geometric layout of various feature preferences. The perturbation analysis is analogous to solving the Schrodinger equation in a weak periodic potential. Competition between the local isotropic connections which produce patterns of activity via the Turing mechanism and the weaker patchy lateral connections that depend on a neuron's particular set of feature preferences create long wavelength affects analogous to commensurate-incommensurate transitions found in fluid systems under a spatially periodic driving force. In this way we hope to better understand how the intrinsic architecture of the visual cortex can generate patterns of activity that underlie visual hallucinations.

Baker, Tanya I.

202

Using Pattern Search Methods for Surface Structure Determinationof Nanomaterials  

SciTech Connect

Atomic scale surface structure plays an important roleindescribing many properties of materials, especially in the case ofnanomaterials. One of the most effective techniques for surface structuredetermination is low-energy electron diffraction (LEED), which can beused in conjunction with optimization to fit simulated LEED intensitiesto experimental data. This optimization problem has a number ofcharacteristics that make it challenging: it has many local minima, theoptimization variables can be either continuous or categorical, theobjective function can be discontinuous, there are no exact analyticderivatives (and no derivatives at all for categorical variables), andfunction evaluations are expensive. In this study, we show how to apply aparticular class of optimization methods known as pattern search methodsto address these challenges. These methods donot explicitly usederivatives, and are particularly appropriate when categorical variablesare present, an important feature that has not been addressed in previousLEED studies. We have found that pattern search methods can produceexcellent results, compared to previously used methods, both in terms ofperformance and locating optimal results.

Zhao, Zhengji; Meza, Juan; Van Hove, Michel

2006-06-09

203

Innovative pattern reversal displays for visual electrophysiological studies.  

PubMed

Pattern Reversal (PR) stimulation is a frequently used tool in the evaluation of the visual pathway. The PR stimulus consists of a field of black and white segments (usually checks or bars) of constant luminance, which change phase (black to white and white to black) at a given reversal rate. The Pattern Electroretinogram (PERG) is a biological potential that is evoked from the retina upon viewing PR display. Likewise, the Pattern Visual Evoked Potential (PVEP) is a biological potential recorded from the occipital cortex when viewing a PR display. Typically, PR stimuli are presented on a Cathode Ray Tube (CRT) or Liquid Crystal Display (LCD) monitor. This paper presents three modalities to generate pattern reversal stimuli. The three methods are as follows: a display consisting of array of Light Emitting Diodes (LEDs), a display comprised of two miniature projectors, and a display utilizing a modified LCD display in conjunction with a variable polarizer. The proposed stimulators allow for the recording of PERG and PVEP waveforms at much higher rates than are capable with conventional stimulators. Additionally, all three of the alternative PR displays will be able to take advantage of advanced analysis techniques, such as the recently developed Continuous Loop Averaging Deconvolution (CLAD) algorithm. PMID:22254729

Toft-Nielsen, J; Bohorquez, J; Ozdamar, O

2011-01-01

204

Deep ocean search by visual, acoustic, and magnetic sensors  

Microsoft Academic Search

The essential components of a system for ocean floor search are: facilities for safe deployment and retrieval of the search vehicle; a method for accurately determining the position of the ship and the search vehicle at all × suitable sensors and displays; provisions for rapid analysis of data; and facilities and personnel for proper operation and maintenance of the equipment.

C. Buchanan

1971-01-01

205

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

206

On Visual Semantic Algebra (VSA) and the cognitive process of pattern recognition  

Microsoft Academic Search

A new form of denotational mathematics known as visual semantic algebra (VSA) is presented for abstract visual object and architecture manipulation. The cognitive theories for pattern recognition, such as cognitive principles of visual perception and basic mechanisms of object and pattern recognition, are explored. A number of case studies on VSA in pattern recognition are presented to demonstrate VAS' expressive

Yingxu Wang

2008-01-01

207

Information-limited parallel processing in difficult heterogeneous covert visual search.  

PubMed

Difficult visual search is often attributed to time-limited serial attention operations, although neural computations in the early visual system are parallel. Using probabilistic search models (Dosher, Han, & Lu, 2004) and a full time-course analysis of the dynamics of covert visual search, we distinguish unlimited capacity parallel versus serial search mechanisms. Performance is measured for difficult and error-prone searches among heterogeneous background elements and for easy and accurate searches among homogeneous background elements. Contrary to the claims of time-limited serial attention, searches in heterogeneous backgrounds instead exhibited nearly identical search dynamics for display sizes up to 12 items. A review and new analyses indicate that most difficult as well as easy visual searches operate as an unlimited-capacity parallel analysis over the visual field within a single eye fixation, which suggests limitations in the availability of information, not temporal bottlenecks in analysis or comparison. Serial properties likely reflect overt attention expressed in eye movements. PMID:20873936

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

2010-10-01

208

Advanced analysis of free visual exploration patterns in schizophrenia.  

PubMed

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. PMID:24130547

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

2013-10-11

209

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

210

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

PubMed

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. PMID:24093014

Lallier, Marie; Donnadieu, Sophie; Valdois, Sylviane

2013-09-25

211

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

212

Investigating the role of the superior colliculus in active vision with the visual search paradigm.  

PubMed

We review here both the evidence that the functional visuomotor organization of the optic tectum is conserved in the primate superior colliculus (SC) and the evidence for the linking proposition that SC discriminating activity instantiates saccade target selection. We also present new data in response to questions that arose from recent SC visual search studies. First, we observed that SC discriminating activity predicts saccade initiation when monkeys perform an unconstrained search for a target defined by either a single visual feature or a conjunction of two features. Quantitative differences between the results in these two search tasks suggest, however, that SC discriminating activity does not only reflect saccade programming. This finding concurs with visual search studies conducted in posterior parietal cortex and the idea that, during natural active vision, visual attention is shifted concomitantly with saccade programming. Second, the analysis of a large neuronal sample recorded during feature search revealed that visual neurons in the superficial layers do possess discriminating activity. In addition, the hypotheses that there are distinct types of SC neurons in the deeper layers and that they are differently involved in saccade target selection were not substantiated. Third, we found that the discriminating quality of single-neuron activity substantially surpasses the ability of the monkeys to discriminate the target from distracters, raising the possibility that saccade target selection is a noisy process. We discuss these new findings in light of the visual search literature and the view that the SC is a visual salience map for orienting eye movements. PMID:21645096

Shen, Kelly; Valero, Jerome; Day, Gregory S; Paré, Martin

2011-06-01

213

Neural mechanisms of top-down selection during visual search  

Microsoft Academic Search

The brain's representation of visual information depends greatly on the behavioral relevance of the viewed stimuli. While in some instances behavioral significance is derived from conspicuity, in many situations significance depends on top-down factors such as the viewer's goals and knowledge. Studies combining neural recordings and behavioral observations have begun to elucidate how the brain selects visual stimuli based on

Narcisse P. Bichot

2001-01-01

214

Long-Term Memory Search across the Visual Brain  

PubMed Central

Signal transmission from the human retina to visual cortex and connectivity of visual brain areas are relatively well understood. How specific visual perceptions transform into corresponding long-term memories remains unknown. Here, I will review recent Blood Oxygenation Level-Dependent functional Magnetic Resonance Imaging (BOLD fMRI) in humans together with molecular biology studies (animal models) aiming to understand how the retinal image gets transformed into so-called visual (retinotropic) maps. The broken object paradigm has been chosen in order to illustrate the complexity of multisensory perception of simple objects subject to visual —rather than semantic— type of memory encoding. The author explores how amygdala projections to the visual cortex affect the memory formation and proposes the choice of experimental techniques needed to explain our massive visual memory capacity. Maintenance of the visual long-term memories is suggested to require recycling of GluR2-containing ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR) and ?2-adrenoreceptors at the postsynaptic membrane, which critically depends on the catalytic activity of the N-ethylmaleimide-sensitive factor (NSF) and protein kinase PKM?.

Fedurco, Milan

2012-01-01

215

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

216

Overlapping multivoxel patterns for two levels of visual expectation.  

PubMed

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). PMID:23630488

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

2013-04-25

217

Local visual energy mechanisms revealed by detection of global patterns.  

PubMed

A central goal of visual neuroscience is to relate the selectivity of individual neurons to perceptual judgments, such as detection of a visual pattern at low contrast or in noise. Since neurons in early areas of visual cortex carry information only about a local patch of the image, detection of global patterns must entail spatial pooling over many such neurons. Physiological methods provide access to local detection mechanisms at the single-neuron level but do not reveal how neural responses are combined to determine the perceptual decision. Behavioral methods provide access to perceptual judgments of a global stimulus but typically do not reveal the selectivity of the individual neurons underlying detection. Here we show how the existence of a nonlinearity in spatial pooling does allow properties of these early mechanisms to be estimated from behavioral responses to global stimuli. As an example, we consider detection of large-field sinusoidal gratings in noise. Based on human behavioral data, we estimate the length and width tuning of the local detection mechanisms and show that it is roughly consistent with the tuning of individual neurons in primary visual cortex of primate. We also show that a local energy model of pooling based on these estimated receptive fields is much more predictive of human judgments than competing models, such as probability summation. In addition to revealing underlying properties of early detection and spatial integration mechanisms in human cortex, our findings open a window on new methods for relating system-level perceptual judgments to neuron-level processing. PMID:22423090

Morgenstern, Yaniv; Elder, James H

2012-03-14

218

From salience to saccades: multiple-alternative gated stochastic accumulator model of visual search.  

PubMed

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. PMID:22399766

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

2012-03-01

219

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

220

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

221

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

222

The role of color in visual search in real-world scenes: Evidence from contextual cuing  

Microsoft Academic Search

Because the importance of color in visual tasks such as object identification and scene memory has been debated, we sought\\u000a to determine whether color is used to guide visual search in contextual cuing with real-world scenes. In Experiment 1, participants\\u000a searched for targets in repeated scenes that were shown in one of three conditions: natural colors, unnatural colors that\\u000a remained

Krista A. Ehinger; James R. Brockmole

2008-01-01

223

Visual Search in Learning Disabled and Hyperactive Boys.  

ERIC Educational Resources Information Center

|Twelve learning disabled (LD), 12 learning disabled hyperactive (LDH) and 12 hyperactive (H) boys (6-11 years old) participated in an investigation of selective attention. Ss were asked to search for a target letter embedded within an array of noise letters. Two variations were included: one involving a simultaneous search for four possible…

McIntyre, Curtis W.; And Others

224

Searching the Visual Arts: An Analysis of Online Information Access.  

ERIC Educational Resources Information Center

|A search for stained glass bibliographic information using DIALINDEX identified 57 DIALOG files from a variety of subject categories and 646 citations as relevant. Files include applied science, biological sciences, chemistry, engineering, environment/pollution, people, business research, and public affairs. Eleven figures illustrate the search

Brady, Darlene; Serban, William

1981-01-01

225

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

226

LFRP-search: multi-layer ranked visual faceted search: an approach to cope with complex search situations  

Microsoft Academic Search

In enterprise search scenarios information needs are quite diverse. If users know exactly which items they are looking for, they need support in known-item searches. But often information needs are vague and unclear, which means that users cannot explicitly define the search criteria that specify their search request. In these cases, exploratory search approaches are necessary to support users in

Raiko Eckstein; Andreas Henrich; Nadine Weber

2010-01-01

227

In situ visualization of telomere elongation patterns in human cells.  

PubMed

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. PMID:23963699

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

2013-08-19

228

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

229

Detection of Emotional Faces: Salient Physical Features Guide Effective Visual Search  

ERIC Educational Resources Information Center

|In this study, the authors investigated how salient visual features capture attention and facilitate detection of emotional facial expressions. In a visual search task, a target emotional face (happy, disgusted, fearful, angry, sad, or surprised) was presented in an array of neutral faces. Faster detection of happy and, to a lesser extent,…

Calvo, Manuel G.; Nummenmaa, Lauri

2008-01-01

230

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

231

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

232

The Role of Target-Distractor Relationships in Guiding Attention and the Eyes in Visual Search  

ERIC Educational Resources Information Center

|Current models of visual search assume that visual attention can be guided by tuning attention toward specific feature values (e.g., particular size, color) or by inhibiting the features of the irrelevant nontargets. The present study demonstrates that attention and eye movements can also be guided by a relational specification of how the target…

Becker, Stefanie I.

2010-01-01

233

An exploratory study of tag-based visual interfaces for searching folksonomies  

Microsoft Academic Search

Aesthetic features such as animation, 3D interaction, and visual metaphors are becoming commonplace in multimedia search interfaces. However, it is unclear which attributes are needed to encourage people to use these interfaces on an ongoing basis. To design a visual interface that will elicit continual use, we first need to establish a better understanding of users' goals and strategies, in

Javier Diaz; Keyun Hu; Melanie Tory

2009-01-01

234

Detection of Emotional Faces: Salient Physical Features Guide Effective Visual Search  

ERIC Educational Resources Information Center

In this study, the authors investigated how salient visual features capture attention and facilitate detection of emotional facial expressions. In a visual search task, a target emotional face (happy, disgusted, fearful, angry, sad, or surprised) was presented in an array of neutral faces. Faster detection of happy and, to a lesser extent,…

Calvo, Manuel G.; Nummenmaa, Lauri

2008-01-01

235

Space-based and object-based capacity limitations in visual search  

Microsoft Academic Search

Space-based accounts of visual attention assume that we select a limited spatial region independent of the number of objects it contains. In contrast, object-based accounts suggest that we select objects independent of their location. We investigated the boundary conditions on the selection modes of attention in a series of tachistoscopic visual search tasks, where the nature of capacity limitations on

Gisela Müller-Plath; Katrin Elsner

2007-01-01

236

The Effects of Presentation Method and Information Density on Visual Search Ability and Working Memory Load  

ERIC Educational Resources Information Center

|This study investigates the effects of successive and simultaneous information presentation methods on learner's visual search ability and working memory load for different information densities. Since the processing of information in the brain depends on the capacity of visual short-term memory (VSTM), the limited information processing capacity…

Chang, Ting-Wen; Kinshuk; Chen, Nian-Shing; Yu, Pao-Ta

2012-01-01

237

Dynamic Modulation of Local Population Activity by Rhythm Phase in Human Occipital Cortex During a Visual Search Task  

PubMed Central

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.

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

238

Learning by Selection: Visual Search and Object Perception in Young Infants  

Microsoft Academic Search

The authors examined how visual selection mechanisms may relate to developing cognitive functions in infancy. Twenty-two 3-month-old infants were tested in 2 tasks on the same day: perceptual completion and visual search. In the perceptual completion task, infants were habituated to a partly occluded moving rod and subsequently presented with unoccluded broken and complete rod test stimuli. In the visual

Dima Amso; Scott P. Johnson

2006-01-01

239

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

240

Performance of visual search tasks from various types of contour information.  

PubMed

A recently proposed visual aid for patients with a restricted visual field (tunnel vision) combines a see-through head-mounted display and a simultaneous minified contour view of the wide-field image of the environment. Such a widening of the effective visual field is helpful for tasks, such as visual search, mobility, and orientation. The sufficiency of image contours for performing everyday visual tasks is of major importance for this application, as well as for other applications, and for basic understanding of human vision. This research aims is to examine and compare the use of different types of automatically created contours, and contour representations, for practical everyday visual operations using commonly observed images. The visual operations include visual searching for items, such as cutlery, housewares, etc. Considering different recognition levels, identification of an object is distinguished from mere detection (when the object is not necessarily identified). Some nonconventional visual-based contour representations were developed for this purpose. Experiments were performed with normal-vision subjects by superposing contours of the wide field of the scene over a narrow field (see-through) background. From the results, it appears that about 85% success is obtained for searched object identification when the best contour versions are employed. Pilot experiments with video simulations are reported at the end of the paper. PMID:23456115

Itan, Liron; Yitzhaky, Yitzhak

2013-03-01

241

Animating streamlines with repeated asymmetric patterns for steady flow visualization  

NASA Astrophysics Data System (ADS)

Animation provides intuitive cueing for revealing essential spatial-temporal features of data in scientific visualization. This paper explores the design of Repeated Asymmetric Patterns (RAPs) in animating evenly-spaced color-mapped streamlines for dense accurate visualization of complex steady flows. We present a smooth cyclic variable-speed RAP animation model that performs velocity (magnitude) integral luminance transition on streamlines. This model is extended with inter-streamline synchronization in luminance varying along the tangential direction to emulate orthogonal advancing waves from a geometry-based flow representation, and then with evenly-spaced hue differing in the orthogonal direction to construct tangential flow streaks. To weave these two mutually dual sets of patterns, we propose an energy-decreasing strategy that adopts an iterative yet efficient procedure for determining the luminance phase and hue of each streamline in HSL color space. We also employ adaptive luminance interleaving in the direction perpendicular to the flow to increase the contrast between streamlines.

Yeh, Chih-Kuo; Liu, Zhanping; Lee, Tong-Yee

2012-01-01

242

Heavy stable charged particles search by novel pattern comparator processor  

NASA Astrophysics Data System (ADS)

This paper describes the idea of the particle recognition at the Pattern Comparator Boards at the RPC detector at the CMS experiment at the LHC at CERN. This solution enables the muons and the Heavy Stable Charged Particles recognition and distinguishing. The described algorithms are implemented in the FPGA structures. They are able to realise the fast analysis of the data from the whole system and work on the reliable triggering decision with the same delay. The implementation is compared with the other solutions. The further development of the RPC system for the HSCPs search is described. Those solutions should provide the reliable data about the hipotetical existence of the HSCPs.

Zago?dzi?ska, A.; Po?niak, K. T.; Romaniuk, R.

2012-05-01

243

Developmental Aspects of Temporal and Spatial Visual Attention: Insights from the Attentional Blink and Visual Search Tasks  

Microsoft Academic Search

Frontal regions of the human cortex are thought to reach full maturation last in the course of development. The present report examines such development in the context of attentional tasks in the temporal (e.g., the attentional blink, AB, paradigm) and spatial (e.g., the visual search, VS, paradigm) domains. Here we show that the recovery from AB is progressively longer with

Frances Garrad-Cole; Kimron L. Shapiro; Guillaume Thierry

2011-01-01

244

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

245

Cortical Dynamics of Contextually Cued Attentive Visual Learning and Search: Spatial and Object Evidence Accumulation  

ERIC Educational Resources Information Center

How do humans use target-predictive contextual information to facilitate visual search? How are consistently paired scenic objects and positions learned and used to more efficiently guide search in familiar scenes? For example, humans can learn that a certain combination of objects may define a context for a kitchen and trigger a more efficient…

Huang, Tsung-Ren; Grossberg, Stephen

2010-01-01

246

The role of working memory and long-term memory in visual search  

Microsoft Academic Search

Models of attentional deployment in visual search commonly specify that the short-term, or working memory, system plays a central role in biasing attention mechanisms to select task relevant information. In contrast, the role of long-term memory in guiding search is rarely articulated. Our review of recent studies calls for the need to revisit how existing models explain the role of

Geoffrey F. Woodman; Marvin M. Chun

2006-01-01

247

Effect of Stress on Crossmodal Interference During Visual Search.  

National Technical Information Service (NTIS)

A key factor in determining the efficiency of target detection is the influence of distracting information during the search process. Using a response competition paradigm, the present study examined how induced stress influences crossmodal links with res...

F. Morelli P. A. Burton

2006-01-01

248

Visualizing digital library search results with categorical and hierarchical axes  

Microsoft Academic Search

Digital library search results are usually shown as a textual list, with 10-20 items per page. Viewing several thousand search results at once on a two-dimensional display with continuous variables is a promising alternative. Since these displays can overwhelm some users, we created a simplified two-dimensional display that uses categorical and hierarchical axes, called hieraxes. Users appreciate the meaningful and

Ben Shneiderman; David Feldman; Anne Rose; Xavier Ferré Grau

2000-01-01

249

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

250

Learning to See: Patterned visual activity and the development of visual function  

PubMed Central

To successfully interact with their environment, developing organisms need to correctly process sensory information and generate motor output appropriate to their size and structure. Patterned sensory experience has long been known to induce various forms of developmental plasticity which ultimately shape mature neural circuits. Yet these same types of plasticity also allow developing organisms to respond appropriately to the external world by dynamically adapting neural circuit function to ongoing changes in brain circuitry and sensory input. Recent work on the visual system of frogs and fish has provided an unprecedented view into how visual experience dynamically affects circuit function at many levels, ranging from gene expression to network function, ultimately leading to system-wide functional adaptations.

Ruthazer, Edward S.; Aizenman, Carlos D.

2012-01-01

251

Model-Driven Development of Audio-Visual Web Search Applications: The PHAROS Demonstration  

Microsoft Academic Search

PHAROS is an EU-founded project aimed at building a platform for advanced audiovisual search applications. In this demo we\\u000a show the application of a Model-Driven Development (MDD) approach to the PHAROS demonstrator, which consists of an audio-visual\\u000a Web search portal. The demo highlights the peculiar needs of search based applications and describes how existing MDD approaches\\u000a can help fulfilling such

Alessandro Bozzon; Marco Brambilla; Piero Fraternali

2009-01-01

252

The linear separability effect in color visual search: Ruling out the additive color hypothesis  

Microsoft Academic Search

Bauer, Jolicoeur, and Cowan (1996b, 1996c) demonstrated difficult visual search for color targets that were not linearly separable\\u000a (in color space) from two distractor colors and easier search for linearly separable targets. This suggested that search is\\u000a mediated by a chromatically linear discrimination mechanism (see D’Zmura, 1991). However, in those experiments, the targets\\u000a that were not linearly separable fell midway

Ben Bauer; Pierre Jolicoeur; William B. Cowan

1998-01-01

253

Visual Search Times Assessed Without Reaction Times: A New Method and an Application to Aging  

Microsoft Academic Search

We consider several ways in which the interpretation of reaction time (RT) data might confound differences in visual search rates with non-search-related factors. To determine whether estimates of search rates for groups differing in age suffered this problem, we compared estimates provided by the RT method with those obtained using a forced-choice method with limited-duration stimuli. The forced-choice method provided

James L. Zacks; Rose T. Zacks

1993-01-01

254

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

255

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

256

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

257

The Attention Operating Characteristic: Examples from Visual Search  

Microsoft Academic Search

Even in the absence of eye movements, we show that subjects are able, upon instruction, to selectively attend to certain kinds of targets and parts of visual arrays. The major mechanism of altering attention is the switching of attention from trial to trial, although intermediate states of shared attention do occur. Attention operating characteristics are shown to be a useful

George Sperling; Melvin J. Melchner

1978-01-01

258

Informed visual search: Combining attention and object recognition  

Microsoft Academic Search

This paper studies the sequential object recogni- tion problem faced by a mobile robot searching for specific objects within a cluttered environment. In contrast to current state-of-the-art object recognition solutions which are evaluated on databases of static images, the system described in this paper employs an active strategy based on identifying potential objects using an attention mechanism and planning to

Per-erik Forssén; David Meger; Kevin Lai; Scott Helmer; James J. Little; David G. Lowe

2008-01-01

259

Initial Scene Representations Facilitate Eye Movement Guidance in Visual Search  

ERIC Educational Resources Information Center

What role does the initial glimpse of a scene play in subsequent eye movement guidance? In 4 experiments, a brief scene preview was followed by object search through the scene via a small moving window that was tied to fixation position. Experiment 1 demonstrated that the scene preview resulted in more efficient eye movements compared with a…

Castelhano, Monica S.; Henderson, John M.

2007-01-01

260

Searching for Complex Human Activities with No Visual Examples  

Microsoft Academic Search

We describe a method of representing human ac- tivities that allows a collection of motions to be queried without examples, using a simple and effective query lan- guage. Our approach is based on units of activity at seg- ments of the body, that can be composed across space and across the body to produce complex queries. The presence of search

David A. Forsyth

2008-01-01

261

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

262

Pattern adaptation and cross-orientation interactions in the primary visual cortex  

Microsoft Academic Search

The responsiveness of neurons in the primary visual cortex (V1) is substantially reduced after a few seconds of visual stimulation with an effective pattern. This phenomenon, called pattern adaptation, is uniquely cortical and is the likely substrate of a variety of perceptual after-effects. While adaptation to a given pattern reduces the responses of V1 neurons to all subsequently viewed test

Matteo Carandini; J. Anthony Movshon; David Ferster

1998-01-01

263

Generation of fractal patterns for probing the visual memory.  

PubMed

The effective use of computer-generated pictures as a trial-unique probe for studying the visual memory is described. The shape of the pattern is determined by means of a fractal algorithm with pseudorandom parameters. This method enables us to easily obtain thousands of moderately complex and sufficiently diversified pictures in series from a given number which serves as the seed of a pseudorandom number generator. We can thereby create a new and unique set of pictures if a new seed is given, as well as retrieve exactly the same pictures in the same sequence as when the original seed is given. These properties eliminate the demand for the massive memory space in a computer otherwise needed to store the entire set of stimulus pictures. PMID:1660991

Miyashita, Y; Higuchi, S; Sakai, K; Masui, N

1991-10-01

264

"Hot" facilitation of "cool" processing: emotional distraction can enhance priming of visual search.  

PubMed

Emotional stimuli often capture attention and disrupt effortful cognitive processing. However, cognitive processes vary in the degree to which they require effort. We investigated the impact of emotional pictures on visual search and on automatic priming of search. Observers performed visual search after task-irrelevant neutral or emotionally evocative photographs. Search performance was generally impaired after emotional pictures, but improvement (measured both with inverse efficiency and sensitivity to briefly presented targets) as a function of incremental between-trial target-color repetition was strongest after emotional pictures. For observers showing the largest general effect of emotional pictures, there was a reversal, with performance becoming better after neutral pictures than after four or more trials containing the same search target. This suggests that although emotional pictures disrupt effortful attention, this detriment can be overcome--to the point where performance is enhanced by emotional stimuli--when the task involves prepotent task priorities. PMID:22642218

Kristjánsson, Árni; Óladóttir, Berglind; Most, Steven B

2012-05-28

265

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

PubMed

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. PMID:23917381

Imura, Tomoko; Tomonaga, Masaki

2013-08-01

266

Visual Iconic Patterns of Instant Messaging: Steps Towards Understanding Visual Conversations  

NASA Astrophysics Data System (ADS)

An Instant Messaging (IM) conversation is a dynamic communication register made up of text, images, animation and sound played out on a screen with potentially several parallel conversations and activities all within a physical environment. This article first examines how best to capture this unique gestalt using in situ recording techniques (video, screen capture, XML logs) which highlight the micro-phenomenal level of the exchange and the macro-social level of the interaction. Of particular interest are smileys first as cultural artifacts in CMC in general then as linguistic markers. A brief taxonomy of these markers is proposed in an attempt to clarify their frequency and patterns of their use. Then, focus is placed on their importance as perceptual cues which facilitate communication, while also serving as emotive and emphatic functional markers. We try to demonstrate that the use of smileys and animation is not arbitrary but an organized interactional and structured practice. Finally, we discuss how the study of visual markers in IM could inform the study of other visual conversation codes, such as sign languages, which also have co-produced, physical behavior, suggesting the possibility of a visual phonology.

Bays, Hillary

267

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

268

Predicting search time in visually cluttered scenes using the fuzzy logic approach  

NASA Astrophysics Data System (ADS)

The mean search time of observers searching for targets in visual scenes with clutter is computed using the fuzzy logic approach (FLA). The FLA is presented as a robust method for the computational of search times and/or probabilities of detection for treated vehicles. The Mamdani/Assilian and Sugeno models have been investigated and are compared. The Search_2 dataset from TNO is used to build and validate the fuzzy logic approach for target detection modeling. The input parameters are: local luminance, range, aspect, width, and wavelet edge points, and the single output is search time. The Mamdani/Assilian model gave predicted mean search times for data not used in the training set that had a 0.957 correlation to the field search times. The data set is reduced using a clustering method, then modeled using the FLA, and results are compared to experiment.

Meitzler, Thomas J.; Sohn, Euijung; Singh, Harpreet; Elgarhi, Abdelakrim; Nam, Deok H.

2001-09-01

269

Neural Control of Visual Search by Frontal Eye Field: Effects of Unexpected Target Displacement on Visual Selection and Saccade Preparation  

PubMed Central

The dynamics of visual selection and saccade preparation by the frontal eye field was investigated in macaque monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. A race model accounts for the probabilities and latencies of saccades to the initial and final singleton locations and provides a measure of the duration of a covert compensation process—target-step reaction time. When the target stepped out of a movement field, noncompensated saccades to the original location were produced when movement-related activity grew rapidly to a threshold. Compensated saccades to the final location were produced when the growth of the original movement-related activity was interrupted within target-step reaction time and was replaced by activation of other neurons producing the compensated saccade. When the target stepped into a receptive field, visual neurons selected the new target location regardless of the monkeys’ response. When the target stepped out of a receptive field most visual neurons maintained the representation of the original target location, but a minority of visual neurons showed reduced activity. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation.

Murthy, Aditya; Ray, Supriya; Shorter, Stephanie M.; Schall, Jeffrey D.; Thompson, Kirk G.

2009-01-01

270

Visualizing Document Classification: A Search Aid for the Digital Library  

Microsoft Academic Search

The recent explosion of the internet has made digital libraries popular. The user-friendly interface of Web browsers allows\\u000a a user much easier access to the digital library. However, to retrieve relevant documents from the digital library, the user\\u000a is provided with a search interface consisting of one input field and one push button. Most users type in a single keyword,

Yew-huey Liu; Paul Dantzig; Martin Sachs; James T. Corey; Mark T. Hinnebusch; Marc Damashek

1998-01-01

271

On the application of evolutionary pattern search algorithms  

SciTech Connect

This paper presents an experimental evaluation of evolutionary pattern search algorithms (EPSAs). Our experimental evaluation of EPSAs indicates that EPSAs can achieve similar performance to EAs on challenging global optimization problems. Additionally, we describe a stopping rule for EPSAs that reliably terminated them near a stationary point of the objective function. The ability for EPSAs to reliably terminate near stationary points offers a practical advantage over other EAs, which are typically stopped by heuristic stopping rules or simple bounds on the number of iterations. Our experiments also illustrate how the rate of the crossover operator can influence the tradeoff between the number of iterations before termination and the quality of the solution found by an EPSA.

Hart, W.E.

1997-02-01

272

PTree: pattern-based, stochastic search for maximum parsimony phylogenies.  

PubMed

Phylogenetic reconstruction is vital to analyzing the evolutionary relationship of genes within and across populations of different species. Nowadays, with next generation sequencing technologies producing sets comprising thousands of sequences, robust identification of the tree topology, which is optimal according to standard criteria such as maximum parsimony, maximum likelihood or posterior probability, with phylogenetic inference methods is a computationally very demanding task. Here, we describe a stochastic search method for a maximum parsimony tree, implemented in a software package we named PTree. Our method is based on a new pattern-based technique that enables us to infer intermediate sequences efficiently where the incorporation of these sequences in the current tree topology yields a phylogenetic tree with a lower cost. Evaluation across multiple datasets showed that our method is comparable to the algorithms implemented in PAUP* or TNT, which are widely used by the bioinformatics community, in terms of topological accuracy and runtime. We show that our method can process large-scale datasets of 1,000-8,000 sequences. We believe that our novel pattern-based method enriches the current set of tools and methods for phylogenetic tree inference. The software is available under: http://algbio.cs.uni-duesseldorf.de/webapps/wa-download/. PMID:23825794

Gregor, Ivan; Steinbrück, Lars; McHardy, Alice C

2013-06-25

273

PTree: pattern-based, stochastic search for maximum parsimony phylogenies  

PubMed Central

Phylogenetic reconstruction is vital to analyzing the evolutionary relationship of genes within and across populations of different species. Nowadays, with next generation sequencing technologies producing sets comprising thousands of sequences, robust identification of the tree topology, which is optimal according to standard criteria such as maximum parsimony, maximum likelihood or posterior probability, with phylogenetic inference methods is a computationally very demanding task. Here, we describe a stochastic search method for a maximum parsimony tree, implemented in a software package we named PTree. Our method is based on a new pattern-based technique that enables us to infer intermediate sequences efficiently where the incorporation of these sequences in the current tree topology yields a phylogenetic tree with a lower cost. Evaluation across multiple datasets showed that our method is comparable to the algorithms implemented in PAUP* or TNT, which are widely used by the bioinformatics community, in terms of topological accuracy and runtime. We show that our method can process large-scale datasets of 1,000–8,000 sequences. We believe that our novel pattern-based method enriches the current set of tools and methods for phylogenetic tree inference. The software is available under: http://algbio.cs.uni-duesseldorf.de/webapps/wa-download/.

Gregor, Ivan; Steinbruck, Lars

2013-01-01

274

Gene prediction by pattern recognition and homology search  

SciTech Connect

This paper presents an algorithm for combining pattern recognition-based exon prediction and database homology search in gene model construction. The goal is to use homologous genes or partial genes existing in the database as reference models while constructing (multiple) gene models from exon candidates predicted by pattern recognition methods. A unified framework for gene modeling is used for genes ranging from situations with strong homology to no homology in the database. To maximally use the homology information available, the algorithm applies homology on three levels: (1) exon candidate evaluation, (2) gene-segment construction with a reference model, and (3) (complete) gene modeling. Preliminary testing has been done on the algorithm. Test results show that (a) perfect gene modeling can be expected when the initial exon predictions are reasonably good and a strong homology exists in the database; (b) homology (not necessarily strong) in general helps improve the accuracy of gene modeling; (c) multiple gene modeling becomes feasible when homology exists in the database for the involved genes.

Xu, Y.; Uberbacher, E.C.

1996-05-01

275

Change Blindness in Children With ADHD: A Selective Impairment in Visual Search?  

PubMed

Objective: This study evaluated change blindness and visual search efficiency in children with ADHD in searching for central and marginal changes. Method: A total of 36 drug-naïve children (18 ADHD/18 controls) performed a flicker task that included changes in objects of central or marginal interest. The task required observers to search for a change until they detected it. Results: Children with ADHD performed more slowly and less accurately than did typically developing children, specifically in detecting marginal-interest changes. Conclusion: In contrast to more standard visual search tasks, flicker tasks seem to be more sensitive to highlight focused attention deficits in children diagnosed with ADHD. Concretely, ADHD attentional deficits were more apparent when the task involved serial top-down strategies. PMID:22334620

Maccari, Lisa; Casagrande, Maria; Martella, Diana; Anolfo, Mariagrazia; Rosa, Caterina; Fuentes, Luis J; Pasini, Augusto

2012-02-14

276

Patterns of non-embolic transient monocular visual field loss.  

PubMed

The aim of this study was to systematically describe the semiology of non-embolic transient monocular visual field loss (neTMVL). We conducted a retrospective case note analysis of patients from Moorfields Eye Hospital (1995-2007). The variables analysed were age, age of onset, gender, past medical history or family history of migraine, eye affected, onset, duration and offset, perception (pattern, positive and negative symptoms), associated headache and autonomic symptoms, attack frequency, and treatment response to nifedipine. We identified 77 patients (28 male and 49 female). Mean age of onset was 37 years (range 14-77 years). The neTMVL was limited to the right eye in 36 % to the left in 47 % and occurred independently in either eye in 5 % of cases. A past medical history of migraine was present in 12 % and a family history in 8 %. Headache followed neTMVL in 14 % and was associated with autonomic features in 3 %. The neTMB was perceived as grey in 35 %, white in 21 %, black in 16 % and as phosphenes in 9 %. Most frequently neTMVL was patchy 20 %. Recovery of vision frequently resembled attack onset in reverse. In 3 patients without associated headache the loss of vision was permanent. Treatment with nifedipine was initiated in 13 patients with an attack frequency of more than one per week and reduced the attack frequency in all. In conclusion, this large series of patients with neTMVL permits classification into five types of reversible visual field loss (grey, white, black, phosphenes, patchy). Treatment response to nifidipine suggests some attacks to be caused by vasospasm. PMID:23564298

Petzold, Axel; Islam, Niaz; Plant, G T

2013-04-06

277

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

278

Visual search in children and adults: Top-down and bottom-up mechanisms  

Microsoft Academic Search

Three experiments investigated visual search for targets that differed from distractors in colour, size, or orientation. In one condition the target was defined by a conjunction of these features, while in the other condition the target was the odd one out. In all experiments, 6–7- and 9–10-year-old children were compared with young adults. Experiment 1 showed that children's search differed

Nick Donnelly; Kyle Cave; Rebecca Greenway; Julie A. Hadwin; Jim Stevenson; Edmund Sonuga-Barke

2007-01-01

279

Preemption effects in visual search: Evidence for low-level grouping  

Microsoft Academic Search

Experiments are presented showing that visual search for Mueller-Lyer (ML) stimuli is based on complete configurations, rather than component segments. Segments easily detected in isolation were difficult to detect when embedded in a configuration, indicating preemption by low-level groups. This pre-emption, which caused stimulus components to become inaccessible to rapid search, was an all-or-nothing effect, and so could serve as

Ronald A. Rensink; James T. Enns

1995-01-01

280

Efficient "pop-out" visual search elicits sustained broadband ? activity in the dorsal attention network.  

PubMed

An object that differs markedly from its surrounding-for example, a red cherry among green leaves-seems to pop out effortlessly in our visual experience. The rapid detection of salient targets, independently of the number of other items in the scene, is thought to be mediated by efficient search brain mechanisms. It is not clear, however, whether efficient search is actually an "effortless" bottom-up process or whether it also involves regions of the prefrontal cortex generally associated with top-down sustained attention. We addressed this question with intracranial EEG (iEEG) recordings designed to identify brain regions underlying a classic visual search task and correlate neural activity with target detection latencies on a trial-by-trial basis with high temporal precision recordings of these regions in epileptic patients. The spatio-temporal dynamics of single-trial spectral analysis of iEEG recordings revealed sustained energy increases in a broad gamma band (50-150 Hz) throughout the duration of the search process in the entire dorsal attention network both in efficient and inefficient search conditions. By contrast to extensive theoretical and experimental indications that efficient search relies exclusively on transient bottom-up processes in visual areas, we found that efficient search is mediated by sustained gamma activity in the dorsal lateral prefrontal cortex and the anterior cingulate cortex, alongside the superior parietal cortex and the frontal eye field. Our findings support the hypothesis that active visual search systematically involves the frontal-parietal attention network and therefore, executive attention resources, regardless of target saliency. PMID:22399764

Ossandón, Tomas; Vidal, Juan R; Ciumas, Carolina; Jerbi, Karim; Hamamé, Carlos M; Dalal, Sarang S; Bertrand, Olivier; Minotti, Lorella; Kahane, Philippe; Lachaux, Jean-Philippe

2012-03-01

281

3D Visual Design for Mobile Search Result on 3G Mobile Phone  

Microsoft Academic Search

The high-speed connection of 3G network has transferred cell-phone applications’ bottleneck from network speed to both the performance of hardware and software and the presentational layer of applications. The 3D visualization on search results for mobile search client can meet the needs of 3G new business. And this technology can be widely used in the areas such as product display,

Yan Yan; Lin Kunhui

2010-01-01

282

Mental workload while driving: effects on visual search, discrimination, and decision making.  

PubMed

The effects of mental workload on visual search and decision making were studied in real traffic conditions with 12 participants who drove an instrumented car. Mental workload was manipulated by having participants perform several mental tasks while driving. A simultaneous visual-detection and discrimination test was used as performance criteria. Mental tasks produced spatial gaze concentration and visual-detection impairment, although no tunnel vision occurred. According to ocular behavior analysis, this impairment was due to late detection and poor identification more than to response selection. Verbal acquisition tasks were innocuous compared with production tasks, and complex conversations, whether by phone or with a passenger, are dangerous for road safety. PMID:12877271

Recarte, Miguel A; Nunes, Luis M

2003-06-01

283

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. (PsycINFO Database Record (c) 2013 APA, all rights reserved). PMID:23163788

Cain, Matthew S; Mitroff, Stephen R

2012-11-19

284

Do honeybees detect colour targets using serial or parallel visual search?  

PubMed

In humans, visual search tasks are commonly used to address the question of how visual attention is allocated in a specific task and how individuals search for a specific object (;target') among other objects (;distractors') that vary in number and complexity. Here, we apply the methodology of visual search experiments to honeybees, which we trained to choose a coloured disc (target) among a varying number of differently coloured discs (distractors). We measured accuracy and decision time as a function of distractor number and colour. We found that for all colour combinations, decision time increased and accuracy decreased with increasing distractor number, whereas performance increased when more targets were present. These findings are characteristic of a serial search in primates, when stimuli are examined sequentially. We found no evidence for parallel search in bees, which would be characterized by a ;pop out' effect, in which the slope of decision time (and accuracy) over distractor number would be near zero. Additionally, we found that decision time and number of errors were significantly higher when bees had to choose a blue target among yellow distractors compared with the inverse colour combination, a phenomenon known as search asymmetry in humans. PMID:16513924

Spaethe, Johannes; Tautz, Jürgen; Chittka, Lars

2006-03-01

285

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

286

Cross Domain Random Walk for Query Intent Pattern Mining from Search Engine Log  

Microsoft Academic Search

Understanding search intents of users through their condensed short queries has attracted much attention both in academia and industry. The search intents of users are generally assumed to be associated with various query patterns, such as \\

Siyu Gu; Jun Yan; Lei Ji; Shuicheng Yan; Junshi Huang; Ning Liu; Ying Chen; Zheng Chen

2011-01-01

287

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

288

Creating and Filtering Structural Data Visualizations using Hygraph Patterns  

Microsoft Academic Search

Data visualization plays a fundamental role in helping users solve complex, information intensive problems in scientific, engineering and business applications. This thesis introduces an original framework for the use of queries to create and filter structural data visualizations (a term we introduce to refer to the diagrammatic display of the relationships of structured data). Hygraphs, a new visual formalism, provides

Mariano P. Consens

1994-01-01

289

Underwater and above-water search patterns of an Arctic seabird: reduced searching at small spatiotemporal scales  

Microsoft Academic Search

How predators vary search patterns in response to prey predictability is poorly known. For example, marine invertebrates may\\u000a be predictable but of low energy value, while fish may be of higher energy value but unpredictable at large (pelagic schools)\\u000a or small (solitary benthics) spatial scales. We investigated the search patterns of the thick-billed murre (Uria lomvia), an Arctic seabird feeding

Kyle Hamish Elliott; Roger D. Bull; Anthony J. Gaston; Gail K. Davoren

2009-01-01

290

A Visualization System for Space-Time and Multivariate Patterns (VIS-STAMP)  

Microsoft Academic Search

The research reported here integrates computational, visual and cartographic methods to develop a geovisual analytic approach for exploring and understanding spatio-temporal and multivariate patterns. The developed methodology and tools can help analysts investigate complex patterns across multivariate, spatial and temporal dimensions via clustering, sorting and visualization. Specifically, the approach involves a self-organizing map, a parallel coordinate plot, several forms of

Diansheng Guo; Jin Chen; Alan M. Maceachren; Ke Liao

2006-01-01

291

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

292

Monocular contribution to the peak time of the binocular pattern visual evoked potential  

Microsoft Academic Search

The contribution of each monocular pathway to the timing of the binocular pattern visual evoked potential was assessed in situations where a significant interocular timing discrepancy was observed. Monocular and binocular pattern visual evoked potentials to 0.5° checks were recorded from normal subjects, normal subjects in whom one eye was blurred, patients with monocular amblyopia, and patients with resolved unilateral

Michelle McKerral; Pierre Lachapelle; François Tremblay; Robert C. Polomeno; Marie-Sylvie Roy; Raquel Beneish; Franco Leporé

1995-01-01

293

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

294

Modeling cognitive effects on visual search for targets in cluttered backgrounds  

NASA Astrophysics Data System (ADS)

To understand how a human operator performs visual search in complex scenes, it is necessary to take into account top- down cognitive biases in addition to bottom-up visual saliency effects. We constructed a model to elucidate the relationship between saliency and cognitive effects in the domain of visual search for distant targets in photo- realistic images of cluttered scenes. In this domain, detecting targets is difficult and requires high visual acuity. Sufficient acuity is only available near the fixation point, i.e. in the fovea. Hence, the choice of fixation points is the most important determinant of whether targets get detected. We developed a model that predicts the 2D distribution of fixation probabilities directly from an image. Fixation probabilities were computed as a function of local contrast (saliency effect) and proximity to the horizon (cognitive effect: distant targets are more likely to be found c close to the horizon). For validation, the model's predictions were compared to ensemble statistics of subjects' actual fixation locations, collected with an eye- tracker. The model's predictions correlated well with the observed data. Disabling the horizon-proximity functionality of the model significantly degraded prediction accuracy, demonstrating that cognitive effects must be accounted for when modeling visual search.

Snorrason, Magnus; Ruda, Harald; Hoffman, James

1998-07-01

295

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

296

Neural anomalies during visual search in schizophrenia patients and unaffected siblings of schizophrenia patients  

Microsoft Academic Search

Schizophrenia patients and their unaffected first-degree relatives exhibit performance deficits on attention tasks, perhaps indicating genetic influence over attentional abnormalities in schizophrenia. To identify anomalous brain function associated with attention in individuals who likely have unexpressed genetic liability for schizophrenia, we studied electrophysiological characteristics of unaffected siblings of schizophrenia patients during a visual serial search task. We gathered behavioral and

Nicholas D. Davenport; Scott R. Sponheim; John J. Stanwyck

2006-01-01

297

Linear and Non-Linear Processes in Visual Search of Letter Displays.  

ERIC Educational Resources Information Center

|Two experiments investigated the linear and nonlinear processes involved in a visual search of letter displays. The displays used in the experiments were well-illuminated 6 x 6 degree or 10 x 10 degree fields containing from 2 to 23 capital As, Bs, or Cs located randomly over the displays. The task of the subjects was to decide as rapidly as…

Donderi, D. C.

298

Delays in Laser Glare Onset Differentially Affect Target-Location Performance in a Visual Search Task.  

National Technical Information Service (NTIS)

The present study examined the effects of low-intensity argon-laser glare on the visual search performance of aviators. Using a modified backward-masking paradigm, subjects were exposed to laser glare, either while seated in a cockpit simulation trainer w...

M. D. Reddix J. A. D'Andrea P. D. Collyer

1991-01-01

299

The Effect of Animated Banner Advertisements on a Visual Search Task  

Microsoft Academic Search

Though animated banners are the predominant form of advertising on the Web, much controversy surrounds their efficacy. Users and experts complain, often bitterly, about being distracted by animation and subjectively believe that their performance suffers when flashing objects are on the screen. A visual search experiment was designed to measure both subjective impression of workload and objective task performance in

Moira Burke; Anthony J. Hornof

300

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

ERIC Educational Resources Information Center

Many visual search experiments measure response 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…

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

2011-01-01

301

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

302

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

303

Relationships Among Display Features, Eye Movement Characteristics, and Reaction Time in Visual Search  

Microsoft Academic Search

The relative contribution of number of fixations and fixation duration to reaction time in visual search was investigated. Ten participants (age 20--24 years) took part in each of two experiments. In Experiment 1, the experimental factors were display type (icon and file name), organization (arrangements with and without grouping), and number of stimuli presented (4, 8, and 16). In Experiment

Atsuo Murata; Nobuyasu Furukawa

2005-01-01

304

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

305

Frontal Eye Field Activity Enhances Object Identification During Covert Visual Search  

PubMed Central

We investigated the link between neuronal activity in the frontal eye field (FEF) and the enhancement of visual processing associated with covert spatial attention in the absence of eye movements. We correlated activity recorded in the FEF of monkeys manually reporting the identity of a visual search target to performance accuracy and reaction time. Monkeys were cued to the most probable target location with a cue array containing a popout color singleton. Neurons exhibited spatially selective responses for the popout cue stimulus and for the target of the search array. The magnitude of activity related to the location of the cue prior to the presentation of the search array was correlated with trends in behavioral performance across valid, invalid, and neutral cue trial conditions. However, the speed and accuracy of the behavioral report on individual trials were predicted by the magnitude of spatial selectivity related to the target to be identified, not for the spatial cue. A minimum level of selectivity was necessary for target detection and a higher level for target identification. Muscimol inactivation of FEF produced spatially selective perceptual deficits in the covert search task that were correlated with the effectiveness of the inactivation and were strongest on invalid cue trials that require an endogenous attention shift. These results demonstrate a strong functional link between FEF activity and covert spatial attention and suggest that spatial signals from FEF directly influence visual processing during the time that a stimulus to be identified is being processed by the visual system.

Monosov, Ilya E.

2009-01-01

306

Visual Search for Object Orientation Can Be Modulated by Canonical Orientation  

ERIC Educational Resources Information Center

|The authors studied the influence of canonical orientation on visual search for object orientation. Displays consisted of pictures of animals whose axis of elongation was either vertical or tilted in their canonical orientation. Target orientation could be either congruent or incongruent with the object's canonical orientation. In Experiment 1,…

Ballaz, Cecile; Boutsen, Luc; Peyrin, Carole; Humphreys, Glyn W.; Marendaz, Christian

2005-01-01

307

Eye Movement and Visual Search: Are There Elementary Abnormalities in Autism?  

ERIC Educational Resources Information Center

|Although atypical eye gaze is commonly observed in autism, little is known about underlying oculomotor abnormalities. Our review of visual search and oculomotor systems in the healthy brain suggests that relevant networks may be partially impaired in autism, given regional abnormalities known from neuroimaging. However, direct oculomotor evidence…

Brenner, Laurie A.; Turner, Katherine C.; Muller, Ralph-Axel

2007-01-01

308

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

ERIC Educational Resources Information Center

|Many visual search experiments measure response 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…

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

2011-01-01

309

Visual Search Asymmetries within Color-Coded and Intensity-Coded Displays  

ERIC Educational Resources Information Center

|Color and intensity coding provide perceptual cues to segregate categories of objects within a visual display, allowing operators to search more efficiently for needed information. Even within a perceptually distinct subset of display elements, however, it may often be useful to prioritize items representing urgent or task-critical information.…

Yamani, Yusuke; McCarley, Jason S.

2010-01-01

310

Visualizing and discovering non-trivial patterns in large time series databases  

Microsoft Academic Search

Data visualization techniques are very important for data analysis, since the human eye has been frequently advocated as the ultimate data-mining tool. However, there has been surprisingly little work on visualizing massive time series datasets. To this end, we developed VizTree, a time series pattern discovery and visualization system based on augmenting suffix trees. VizTree visually summarizes both the global

Jessica Lin; Eamonn J. Keogh; Stefano Lonardi

2005-01-01

311

Predicting search time in visual scenes using the fuzzy logic approach  

NASA Astrophysics Data System (ADS)

The mean search time of observers looking for targets in visual scenes with clutter is computed using the Fuzzy Logic Approach (FLA). The FLA is presented by the authors as a robust method for the computation of search times and or probabilities of detection for signature management decisions. The Mamdani/Assilian and Sugeno models have been investigated and are compared. A 44 image data set from TNO is used to build and validate the fuzzy logic model for detection. The input parameters are the: local luminance, range, aspect, width, wavelet edge points and the single output is search time. The Mamdani/Assilian model gave predicted mean search times from data not used in the training set that had a 0.957 correlation to the field search times. The data set is reduced using a clustering method then modeled using the FLA and results are compared to experiment.

Meitzler, Thomas J.; Sohn, Euijung; Singh, Harpreet; Elgarhi, Abdelakrim

1999-07-01

312

Dynamic Weighting of Feature Dimensions in Visual Search: Behavioral and Psychophysiological Evidence  

PubMed Central

Dimension-based accounts of visual search and selection have significantly contributed to the understanding of the cognitive mechanisms of attention. Extensions of the original approach assuming the existence of dimension-based feature contrast saliency signals that govern the allocation of focal attention have recently been employed to explain the spatial and temporal dynamics of the relative strengths of saliency representations. Here we review behavioral and neurophysiological findings providing evidence for the dynamic trial-by-trial weighting of feature dimensions in a variety of visual search tasks. The examination of the effects of feature and dimension-based inter-trial transitions in feature detection tasks shows that search performance is affected by the change of target-defining dimensions, but not features. The use of the redundant-signals paradigm shows that feature contrast saliency signals are integrated at a pre-selective processing stage. The comparison of feature detection and compound search tasks suggests that the relative significance of dimension-dependent and dimension-independent saliency representations is task-contingent. Empirical findings that explain reduced dimension-based effects in compound search tasks are discussed. Psychophysiological evidence is presented that confirms the assumption that the locus of the effects of feature dimension changes is perceptual pre-selective rather than post-selective response-based. Behavioral and psychophysiological results are considered within in the framework of the dimension weighting account of selective visual attention.

Krummenacher, Joseph; Muller, Hermann J.

2012-01-01

313

Neural correlates of visual search in patients with hereditary retinal dystrophies.  

PubMed

In patients with central visual field scotomata a large part of visual cortex is not adequately stimulated. We investigated evidence for possible upregulation in cortical responses in 22 patients (8 females, 14 males; mean age 41.5 years, range 12-65 years) with central visual field loss due to hereditary retinal dystrophies (Stargardt's disease, other forms of hereditary macular dystrophies and cone-rod dystrophy) and compared their results to those of 22 age-matched controls (11 females, 11 males; mean age, 42.4 years, range, 13-70 years). Using functional magnetic resonance imaging (fMRI) we recorded differences in behavioral and BOLD signal distribution in retinotopic mapping and visual search tasks. Patients with an established preferred retinal locus (PRL) exhibited significantly higher activation in early visual cortex during the visual search task, especially on trials when the target stimuli fell in the vicinity of the PRL. Compared with those with less stable fixation, patients with stable eccentric fixation at the PRL exhibited greater performance levels and more brain activation. Hum Brain Mapp 34:2607-2623, 2013. © 2012 Wiley Periodicals, Inc. PMID:22505353

Plank, Tina; Frolo, Jozef; Farzana, Fatima; Brandl-Rühle, Sabine; Renner, Agnes B; Greenlee, Mark W

2012-04-16

314

Human-guided simple search: combining information visualization and heuristic search  

Microsoft Academic Search

Scheduling, routing, and layout tasks are examples of hard operations-research problems that have broad application in industry. Typical algorithms for these problems combine some form of gradient descent to find local minima with some strategy for escaping nonoptimal local minima and traversing the search space. Our idea is to divide these two subtasks cleanly between human and computer: in our

David Anderson; Emily Anderson; Neal Lesh; Joe Marks; Ken Perlin; David Ratajczak; Kathy Ryall

1999-01-01

315

Neural basis of feature-based contextual effects on visual search behavior  

PubMed Central

Searching for a visual object is known to be adaptable to context, and it is thought to result from the selection of neural representations distributed on a visual salience map, wherein stimulus-driven and goal-directed signals are combined. Here we investigated the neural basis of this adaptability by recording superior colliculus (SC) neurons while three female rhesus monkeys (Macaca mulatta) searched with saccadic eye movements for a target presented in an array of visual stimuli whose feature composition varied from trial to trial. We found that sensory-motor activity associated with distracters was enhanced or suppressed depending on the search array composition and that it corresponded to the monkey's search strategy, as assessed by the distribution of the occasional errant saccades. This feature-related modulation occurred independently from the saccade goal and facilitated the process of saccade target selection. We also observed feature-related enhancement in the activity associated with distracters that had been the search target during the previous session. Consistent with recurrent processing, both feature-related neuronal modulations occurred more than 60 ms after the onset of the visually evoked responses, and their near coincidence with the time of saccade target selection suggests that they are integral to this process. These results suggest that SC neuronal activity is shaped by the visual context as dictated by both stimulus-driven and goal-directed signals. Given the close proximity of the SC to the motor circuit, our findings suggest a direct link between perception and action and no need for distinct salience and motor maps.

Shen, Kelly; Pare, Martin

2012-01-01

316

Studying visual search using systems factorial methodology with target-distractor similarity as the factor  

PubMed Central

Systems factorial technology (SFT) is a theory-driven set of methodologies oriented toward identification of basic mechanisms, such as parallel versus serial processing, of perception and cognition. Studies employing SFT in visual search with small display sizes have repeatedly shown decisive evidence for parallel processing. The first strong evidence for serial processing was recently found in short-term memory search, using target–distractor (T–D) similarity as a key experimental variable (Townsend & Fifi?, 2004). One of the major goals of the present study was to employ T–D similarity in visual search to learn whether this mode of manipulating processing speed would affect the parallel versus serial issue in that domain. The result was a surprising and regular departure from ordinary parallel or serial processing. The most plausible account at present relies on the notion of positively interacting parallel channels.

Fific, Mario; Townsend, James T.; Eidels, Ami

2008-01-01

317

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

318

Sensitive tint visualization of resonance patterns in glass plate  

NASA Astrophysics Data System (ADS)

Photoelastic visualization can be used to establish vibrational modes of solid transparent materials having complicated longitudinal and shear strains. On the other hand, determining the sign of a stress field by the photoelastic visualization is difficult. Color visualization of resonance vibrational modes of a glass plate by using stroboscopic photoelasticity with a sensitive tint plate is described. This technique enables to determine the sign of the stress in acoustic fields.

Yamamoto, Ken; Izuno, Kana; Aoyanagi, Masafumi

2012-05-01

319

The role of auditory and visual models in the production of bimanual tapping patterns.  

PubMed

An experiment was designed to determine the effectiveness of auditory and visual models in the learning of a 2:3 bimanual tapping pattern. Participants were randomly assigned to an auditory model, visual model, auditory + visual model, or a control (visual metronome) group. The task for all groups was to tap a left side force transducer with the left hand and a right side force transducer with the right hand in attempt to produce the desired 2:3 bimanual coordination pattern. The auditory model consisted of a series of tones representing the goal pattern played prior to each practice trial. The visual model consisted of a visual display representing the goal tapping pattern. Visual pacing metronomes were provided to the control group. The right and left side metronomes flashed during the trial in a pattern representing the goal tapping pattern. Subjects in all groups performed 14 practice trials consisting of 15 s each devoted to tapping the goal pattern (total practice time = 3.5 min). A retention test without the aid of the models or metronomes was administered following the practice trials. The results for the model groups indicated extremely effective performance of the bimanual coordination patterns for the auditory, visual, and auditory + visual model conditions with not only the relative, but also the absolute characteristics of the models exhibited during retention testing. Retention performance for the visual metronome condition was less accurate and more variable than the three model conditions. In addition, the auditory + visual model condition resulted in retention performance that was more stable than the auditory model condition. PMID:23229772

Kennedy, Deanna M; Boyle, Jason B; Shea, Charles H

2012-11-15

320

Display size effects in visual search: analyses of reaction time distributions as mixtures.  

PubMed

In a reanalysis of data from Cousineau and Shiffrin (2004) and two new visual search experiments, we used a likelihood ratio test to examine the full distributions of reaction time (RT) for evidence that the display size effect is a mixture-type effect that occurs on only a proportion of trials, leaving RT in the remaining trials unaffected, as is predicted by serial self-terminating search models. Experiment 1 was a reanalysis of Cousineau and Shiffrin's data, for which a mixture effect had previously been established by a bimodal distribution of RTs, and the results confirmed that the likelihood ratio test could also detect this mixture. Experiment 2 applied the likelihood ratio test within a more standard visual search task with a relatively easy target/distractor discrimination, and Experiment 3 applied it within a target identification search task within the same types of stimuli. Neither of these experiments provided any evidence for the mixture-type display size effect predicted by serial self-terminating search models. Overall, these results suggest that serial self-terminating search models may generally be applicable only with relatively difficult target/distractor discriminations, and then only for some participants. In addition, they further illustrate the utility of analysing full RT distributions in addition to mean RT. PMID:19048454

Reynolds, Ann; Miller, Jeff

2008-12-01

321

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

322

Spectral filters can improve reading and visual search in patients with multiple sclerosis.  

PubMed

We investigated the possible benefit for 26 patients with multiple sclerosis of placing Intuitive Overlays (spectral filters) over the page during reading and visual search. Initially all patients were allowed to select an overlay of a colour that reduced perceptual distortion and were tested with and without that overlay. With the coloured overlay, 25/26 patients reported fewer symptoms of visual stress, 50% read at least 20% more quickly and 50% omitted at least 57% fewer targets during visual search. Subsequently, under double-masked conditions 13 randomly-selected patients were given grey overlays,while the remaining 13 gender- and agematched patients were each given an overlay of their individually selected colour. Patients were permitted to use their overlays as and when they wished during the next 2 weeks. The reading and visual search performance of those patients who had received a grey overlay did not change,whereas the performance of those who received an overlay of their selected colour subsequently improved, both when using the overlays and also when not. After testing, the 13 patients who had received a grey overlay returned it prior to subsequent testing. The 13 patients were then each given an overlay of their selected colour and their performance subsequently improved.A large proportion of patients with multiple sclerosis may benefit from the use of spectral overlays. PMID:17934874

Newman Wright, B; Wilkins, A J; Zoukos, Y

2007-10-15

323

Epilepsy and Medication Effects on the Pattern Visual Evoked Potential  

Microsoft Academic Search

Visual disruption in patients diagnosed with epilepsy may be attributable to either the disease itself or to the anti-epileptic drugs prescribed to control the seizures. Effects on visual function may be due to perturbations of the GABAergic neurotransmitter system, since deficits in GABAergic cortical interneurons have been hypothesized to underlie some forms of epilepsy, some anti-epileptic medications increase cortical GABA

Andrew M. Geller; H. Ken. Hudnell; Bradley V. Vaughn; John A. Messenheimer; William K. Boyes

2005-01-01

324

Pattern reversal visually evoked potentials in general anesthesia  

Microsoft Academic Search

Various authors have tried to determine visual acuity both electrophysiologically (Sokol, 1976 and 1978; Marg et al., 1976; Maffei and Fiorentini, 1977) and with psychophysical methods (Teller et al., 1974; Banks and Salapatek, 1976; Atkinson et al., 1976) in awake children. Our experiments try to verify the possibility of assessing visual acuity in children under Ethrane anesthesia. We conclude that

B. Bagolini; A. Penne; S. Fonda; A. Mazzetti

1979-01-01

325

Visual search performance of patients with vision impairment: Effect of JPEG image enhancement  

PubMed Central

Purpose To measure natural image search performance in patients with central vision impairment. To evaluate the performance effect for a JPEG based image enhancement technique using the visual search task. Method 150 JPEG images were presented on a touch screen monitor in either an enhanced or original version to 19 patients (visual acuity 0.4 to 1.2 logMAR, 6/15 to 6/90, 20/50 to 20/300) and 7 normally sighted controls (visual acuity ?0.12 to 0.1 logMAR, 6/4.5 to 6/7.5, 20/15 to 20/25). Each image fell into one of three categories: faces, indoors, and collections. The enhancement was realized by moderately boosting a mid-range spatial frequency band in the discrete cosine transform (DCT) coefficients of the image luminance component. Participants pointed to an object in a picture that matched a given target displayed at the upper-left corner of the monitor. Search performance was quantified by the percentage of correct responses, the median search time of correct responses, and an “integrated performance” measure – the area under the curve of cumulative correct response rate over search time. Results Patients were able to perform the search tasks but their performance was substantially worse than the controls. Search performances for the 3 image categories were significantly different (p?0.001) for all the participants, with searching for faces being the most difficult. When search time and correct response were analyzed separately, the effect of enhancement led to increase in one measure but decrease in another for many patients. Using the integrated performance, it was found that search performance declined with decrease in acuity (p=0.005). An improvement with enhancement was found mainly for the patients whose acuity ranged from 0.4 to 0.8 logMAR (6/15 to 6/38, 20/50 to 20/125). Enhancement conferred a small but significant improvement in integrated performance for indoor and collection images (p=0.025) in the patients. Conclusion Search performance for natural images can be measured in patients with impaired vision to evaluate the effect of image enhancement. Patients with moderate vision loss might benefit from the moderate level of enhancement used here.

Luo, Gang; Satgunam, PremNandhini; Peli, Eli

2012-01-01

326

Activity in V4 Reflects the Direction, But Not the Latency, of Saccades During Visual Search  

PubMed Central

We constantly make eye movements to bring objects of interest onto the fovea for more detailed processing. Activity in area V4, a prestriate visual area, is enhanced at the location corresponding to the target of an eye movement. However, the precise role of activity in V4 in relation to these saccades and the modulation of other cortical areas in the oculomotor system remains unknown. V4 could be a source of visual feature information used to select the eye movement, or alternatively, it could reflect the locus of spatial attention. To test these hypotheses, we trained monkeys on a visual search task in which they were free to move their eyes. We found that activity in area V4 reflected the direction of the upcoming saccade but did not predict the latency of the saccade in contrast to activity in the lateral intraparietal area (LIP). We suggest that the signals in V4, unlike those in LIP, are not directly involved in the generation of the saccade itself but rather are more closely linked to visual perception and attention. Although V4 and LIP have different roles in spatial attention and preparing eye movements, they likely perform complimentary processes during visual search.

Gee, Angela L.; Ipata, Anna E.

2010-01-01

327

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

328

Pattern electroretinogram (PERG) and pattern visual evoked potential (PVEP) in the early stages of Alzheimer's disease  

PubMed Central

Alzheimer’s disease (AD) is one of the most common causes of dementia in the world. Patients with AD frequently complain of vision disturbances that do not manifest as changes in routine ophthalmological examination findings. The main causes of these disturbances are neuropathological changes in the visual cortex, although abnormalities in the retina and optic nerve cannot be excluded. Pattern electroretinogram (PERG) and pattern visual evoked potential (PVEP) tests are commonly used in ophthalmology to estimate bioelectrical function of the retina and optic nerve. The aim of this study was to determine whether retinal and optic nerve function, measured by PERG and PVEP tests, is changed in individuals in the early stages of AD with normal routine ophthalmological examination results. Standard PERG and PVEP tests were performed in 30 eyes of 30 patients with the early stages of AD. The results were compared to 30 eyes of 30 normal healthy controls. PERG and PVEP tests were recorded in accordance with the International Society for Clinical Electrophysiology of Vision (ISCEV) standards. Additionally, neural conduction was measured using retinocortical time (RCT)—the difference between P100-wave latency in PVEP and P50-wave implicit time in PERG. In PERG test, PVEP test, and RCT, statistically significant changes were detected. In PERG examination, increased implicit time of P50-wave (P < 0.03) and amplitudes reductions in P50- and N95-waves (P < 0.0001) were observed. In PVEP examination, increased latency of P100-wave (P < 0.0001) was found. A significant increase in RCT (P < 0.0001) was observed. The most prevalent features were amplitude reduction in N95-wave and increased latency of P100-wave which were seen in 56.7% (17/30) of the AD eyes. In patients with the early stages of AD and normal routine ophthalmological examination results, dysfunction of the retinal ganglion cells as well as of the optic nerve is present, as detected by PERG and PVEP tests. These dysfunctions, at least partially, explain the cause of visual disturbances observed in patients with the early stages of AD.

Lubinski, Wojciech; Potemkowski, Andrzej; Honczarenko, Krystyna

2010-01-01

329

Allocation of attention in texture segregation, visual search, and location-precuing paradigms.  

PubMed

Is there a common mechanism (or set of mechanisms) that controls the allocation of spatial attention in texture segregation, visual search, and location-precuing tasks? This question was addressed by comparing data from a new set of experiments on texture segregation, in which a common set of stimuli was used across the three paradigms. However, when we ranked the scores for the targets on texture segregation speed, search rate, and improvement due to precuing effects, agreement between these measures was less than perfect. Further analyses of these results led to the following conclusions: (a) speed of texture segregation is affected by perceptual aspects of the display other than the attentional salience of a particular target; (b) visual search rate and the size of precuing effects are strongly related over most of the set of targets we used; and (c) some cases in which search rate was not consistent with size of precue effects may be related to the presence of nearby distractors in the search task. PMID:8177962

Cheal, M; Lyon, D R

1994-02-01

330

Integrating space and time in visual search: how the preview benefit is modulated by stereoscopic depth.  

PubMed

We examined visual search for letters that were distributed across both 3 dimensional space, and time. In Experiment 1, when participants had foreknowledge of the depth plane and time interval where targets could appear, search was more efficient if the items could be segmented either by depth or by time (with a 1000 ms preview), and there were increased benefits when the two cues (depth and time) were combined. In Experiments 2 and 3 the target depth plane was always unknown to the participant. In this case, depth cues alone did not facilitate search, though they continued to increase the preview benefit. In Experiment 4 new items in preview search could fall at the same depth as preview items or a new depth. There was a substantial cost to search if the target appeared at a previewed depth. Experiment 5 showed that this cost remained even when participants knew the target would appear at the old depth on 75% of trials. The results indicate that spatial (depth) and temporal cues combine to enhance visual segmentation and selection, and this is accomplished by inhibition of distractors in irrelevant depth planes. PMID:22728923

Dent, Kevin; Braithwaite, Jason J; He, Xun; Humphreys, Glyn W

2012-06-20

331

Visualization of relative flow patterns in centrifugal blood pump  

Microsoft Academic Search

This paper presents computational and flow visualization results on a centrifugal blood pump. 4 impeller designs were tested\\u000a at a rotational speed of 2000 rpm using blood analog as working fluid. All impellers have seven blades but of different geometry\\u000a (Impellers A3, A4, B2 and R7). Flow visualization within the impeller passages was conducted using an image de-rotation system.\\u000a A

Weng Kong Chan; S. C. M Yu; L. P. Chua; Y. W. Wong

2001-01-01

332

Non-Searching for Jobs: Patterns and Payoffs to Non-Searching Across the Work Career  

Microsoft Academic Search

While conventional wisdom suggests that that getting jobs is more about “who you know” than “what you know”, the empirical evidence on job searching shows that people who rely on their personal contacts when searching for a job generally do not receive any benefits over people who use more formal job search methods. Since the most advantaged social groups are

Steve McDonald

2004-01-01

333

Searching, viewing, and visualizing data in the Biomolecular Interaction Network Database (BIND).  

PubMed

The Biomolecular Interaction Network Database (BIND) comprises data from peer-reviewed literature and direct submissions. BIND's data model was the first of its kind to be peer-reviewed prior to database development, and is now a mature standard data format spanning molecular interactions, small molecule chemical reactions, and interfaces from three-dimensional structures, pathways, and genetic interaction networks. BIND supports additional file formats to achieve compatibility with other database efforts, including the HUPO PSI Level 2. BIND's latest software spans over 2000 metadata fields and is constructed using the Java Enterprise Systems software platform. Protocols are provided for searching BIND via the Internet, as well as for viewing and exporting search results or individual records. Furthermore, a protocol is provided for visualizing biomolecular interactions within BIND or for transferring this information to the visualization tools Cytoscape and Cn3D. PMID:18428770

Willis, Randall C; Hogue, Christopher W V

2006-01-01

334

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

335

Analysis and modeling of fixation point selection for visual search in cluttered backgrounds  

NASA Astrophysics Data System (ADS)

Hard-to-see targets are generally only detected by human observers once they have been fixated. Hence, understanding how the human visual system allocates fixation locations is necessary for predicting target detectability. Visual search experiments were conducted where observers searched for military vehicles in cluttered terrain. Instantaneous eye position measurements were collected using an eye tracker. The resulting data was partitioned into fixations and saccades, and analyzed for correlation with various image properties. The fixation data was used to validate out model for predicting fixation locations. This model generates a saliency map from bottom-up image features, such as local contrast. To account for top-down scene understanding effects, a separate cognitive bias map is generated. The combination of these two maps provides a fixation probability map, from which sequences of fixation points were generated.

Snorrason, Magnus; Hoffman, James; Ruda, Harald

2000-07-01

336

Long-term retention of skilled visual search: do young adults retain more than old adults?  

PubMed

Young and old Ss received extensive consistent-mapping visual search practice (3,000 trials). The Ss returned to the laboratory following a 16-month retention interval. Retention of skilled visual search was assessed using the trained stimuli (assessment of retention of stimulus-specific learning) and using new stimuli (assessment of retention of task-specific learning). All Ss, regardless of age group, demonstrated impressive retention. However, age-related retention differences favoring the young were observed when retention of stimulus-specific learning was assessed. No age-related retention differences were observed when task-specific learning was assessed. The data suggest that age-related retention capabilities depend on the type of learning assessed. PMID:8054168

Fisk, A D; Hertzog, C; Lee, M D; Rogers, W A; Anderson-Garlach, M

1994-06-01

337

Sleep-effects on implicit and explicit memory in repeated visual search.  

PubMed

In repeated visual search tasks, facilitation of reaction times (RTs) due to repetition of the spatial arrangement of items occurs independently of RT facilitation due to improvements in general task performance. Whereas the latter represents typical procedural learning, the former is a kind of implicit memory that depends on the medial temporal lobe (MTL) memory system and is impaired in patients with amnesia. A third type of memory that develops during visual search is the observers' explicit knowledge of repeated displays. Here, we used a visual search task to investigate whether procedural memory, implicit contextual cueing, and explicit knowledge of repeated configurations, which all arise independently from the same set of stimuli, are influenced by sleep. Observers participated in two experimental sessions, separated by either a nap or a controlled rest period. In each of the two sessions, they performed a visual search task in combination with an explicit recognition task. We found that (1) across sessions, MTL-independent procedural learning was more pronounced for the nap than rest group. This confirms earlier findings, albeit from different motor and perceptual tasks, showing that procedural memory can benefit from sleep. (2) Likewise, the sleep group compared with the rest group showed enhanced context-dependent configural learning in the second session. This is a novel finding, indicating that the MTL-dependent, implicit memory underlying contextual cueing is also sleep-dependent. (3) By contrast, sleep and wake groups displayed equivalent improvements in explicit recognition memory in the second session. Overall, the current study shows that sleep affects MTL-dependent as well as MTL-independent memory, but it affects different, albeit simultaneously acquired, forms of MTL-dependent memory differentially. PMID:23936363

Geyer, Thomas; Mueller, Hermann J; Assumpcao, Leonardo; Gais, Steffen

2013-08-02

338

THE IMPACT OF ANIMATION TIMING AND LOCATION ON VISUAL SEARCH TASK PERFORMANCE IN THE WEB ENVIRONMENT  

Microsoft Academic Search

Research results from a previous study show that animation as non-primary information significantly reduces information-seeking performance in a web-based environment (Zhang 2000). This study continues to explore the impact of animation timing and location on visual search tasks. The results indicate that (1) animation that appears during the middle or toward the end of an information-seeking task degrades performance more

Ping Zhang

339

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

340

Fear, but not fear-relevance, modulates reaction times in visual search with animal distractors  

Microsoft Academic Search

The research aimed at examining attentional selectivity in a visual search paradigm using pictures of animals that have provided a recurrent threat in an evolutionary perspective (i.e., snakes and spiders) and pictures of animals that have supposedly posed no such threat (i.e., cats and fish). Experiment 1 showed no advantage of fear-relevant stimuli over non-fear-relevant animal stimuli. However, an attentional

Sandra C. Soares; Francisco Esteves; Anders Flykt

2009-01-01

341

Eye Movement and Visual Search: Are There Elementary Abnormalities in Autism?  

Microsoft Academic Search

Although atypical eye gaze is commonly observed in autism, little is known about underlying oculomotor abnormalities. Our\\u000a review of visual search and oculomotor systems in the healthy brain suggests that relevant networks may be partially impaired\\u000a in autism, given regional abnormalities known from neuroimaging. However, direct oculomotor evidence for autism remains limited.\\u000a This gap is critical since oculomotor abnormalities might

Laurie A. Brenner; Katherine C. Turner; Ralph-Axel Müller

2007-01-01

342

Visual supernova searching with the 40 inch telescope at Siding Spring Observatory  

NASA Astrophysics Data System (ADS)

Preliminary results are presented arising from the use of the 40 inch telescope at Siding Spring Observatory for visual supernova hunting over a period of about 18 months. The use of the telescope in this way is continuing. These results are compared with the performance of my 41 cm backyard telescope over the same 18-month period, and with recently announced results from the Perth Observatory's Automated Supernova Search using their 61 cm telescope over a three-year period.

Evans, R.

1997-08-01

343

A method to identify talent: visual search and locomotion behavior in young football players.  

PubMed

The present study examined differences in visual search and locomotor behavior among a group of skilled 10-12 year-old football players. The participants watched video clips of a 4-to-4 position game, presented on a large screen. The participants were asked to take part in the game by choosing the best position for the reception of the ball passed by one of the players in the clip. Participants' visual search and locomotor behavior were collected continuously throughout the presentation of the clip. A within-group comparison was made based upon the participants' interception score, i.e., more at the correct position. The findings show that the high-score group looked more to the ball area, while the players in the low-score group concentrated on the receiving player and on the hips/upper-body region of the passing player. The players in the high-score group covered a significantly greater distance compared to the low-score group. It was concluded that differences in visual search and locomotion behavior can be used as indicators for identifying talented junior football players. PMID:20728954

Savelsbergh, Geert J P; Haans, Sascha H A; Kooijman, Margit K; van Kampen, Paulien M

2010-08-21

344

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

345

Color-coded pattern suppresses visual evoked cortical potentials and electroretinograms  

Microsoft Academic Search

We developed a new visual stimulating system for recording visual evoked cortical potentials and electroretinograms. The stimulus\\u000a was a color checkerboard, in which each check kept its chromaticity but changed its luminance with its corresponding check.\\u000a Color-coded pattern stimuli using red and green checks did not produce visual evoked cortical potentials, while yellow checks\\u000a produced clear responses in a normal

Yoshiaki Shimada; Koichiro Murayama; Emiko Adachi-Usami

1996-01-01

346

Indirect choroidal ruptures: aetiological factors, patterns of ocular damage, and final visual outcome  

Microsoft Academic Search

Indirect choroidal ruptures result from blunt ocular trauma and have a pathognomonic fundal appearance. We analysed a group of 30 patients with indirect choroidal ruptures with specific reference to the circumstances of the injury, the pattern of ocular damage, the cause of any visual loss, and the final visual outcome. Using this analysis we deduce a pathogenetic explanation for the

C M Wood; J Richardson

1990-01-01

347

Response Patterns of Children with Visual Impairments on Measures of Internalized Self-Responsibility.  

ERIC Educational Resources Information Center

|This study investigated the mastery-oriented and learned-helplessness response patterns of children (n=13) with visual impairments in grades 3 to 6 who were divided into two groups, low vision children who were visual learners and nonvisual learners. Subjects were given the Intellectual Achievement Responsibility Questionnaire. No significant…

Spencer, Rebecca A.; Head, Daniel N.; Pysh, Margaret Van Dusen; Chalfant, James C.

1997-01-01

348

Comparison of Visualized Turbine Endwall Secondary Flows and Measured Heat Transfer Patterns.  

National Technical Information Service (NTIS)

Various flow visualization techniques were used to define the secondary 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 Reyn...

R. E. Gaugler L. M. Russell

1983-01-01

349

Protein Sequence Similarity Searches Using Patterns as Seeds  

Microsoft Academic Search

Protein families often are characterized by conservedsequence patterns or motifs. A researcher frequentlywishes to evaluate the significance of a specificpattern within a protein, or to exploit knowledge ofknown motifs to aid the recognition of greatly divergedbut homologous family members. To assist in theseefforts, the pattern-hit initiated BLAST (PHI-BLAST)program described here takes as input both a proteinsequence and a pattern of

Zheng Zhang; A. A. Schaffer; Webb Miller; Thomas L. Madden; David J. Lipman; Eugene V. Koonin; Stephen F. Altschul

1998-01-01

350

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

351

Orientation is different: Interaction between contour integration and feature contrasts in visual search.  

PubMed

Salient items usually capture attention and are beneficial to visual search. Jingling and Tseng (2013), nevertheless, have discovered that a salient collinear column can impair local visual search. The display used in that study had 21 rows and 27 columns of bars, all uniformly horizontal (or vertical) except for one column of bars orthogonally oriented to all other bars, making this unique column of collinear (or noncollinear) bars salient in the display. Observers discriminated an oblique target bar superimposed on one of the bars either in the salient column or in the background. Interestingly, responses were slower for a target in a salient collinear column than in the background. This opens a theoretical question of how contour integration interacts with salience computation, which is addressed here by an examination of how salience modulated the search impairment from the collinear column. We show that the collinear column needs to have a high orientation contrast with its neighbors to exert search interference. A collinear column of high contrast in color or luminance did not produce the same impairment. Our results show that orientation-defined salience interacted with collinear contour differently from other feature dimensions, which is consistent with the neuronal properties in V1. PMID:24023276

Jingling, Li; Tseng, Chia-Huei; Zhaoping, Li

2013-09-10

352

Effect of surface medium on visual search for orientation and size features.  

PubMed

By using a visual search task, this study examined the encoding of orientation and size for stimuli defined in five different surface media: luminance, color, texture, relative motion, and binocular disparity. Results indicated a spatially parallel analysis of size and orientation features for all surface media, with the possible exception of binocular disparity. The data also revealed a search rate asymmetry in the orientation task for all media: Parallel or shallow search functions were obtained for oblique targets in vertical distractors, whereas steeper serial search functions were obtained for vertical targets in oblique distractors. No consistent asymmetry was found for the large and small targets in the size task. There seemed to be common principles of coding in all these different media, suggesting either a single analysis of shape features applied to a common representation or multiple analyses, one for each surface medium, with each extracting a similar set of features. The shared coding principles may facilitate the use of redundancy across media to reduce ambiguities in the locations and shapes of contours in the visual scene. PMID:2144565

Cavanagh, P; Arguin, M; Treisman, A

1990-08-01

353

How much agreement is there in the visual search strategy of experts reading mammograms?  

NASA Astrophysics Data System (ADS)

Previously we have shown that the eyes of expert breast imagers are attracted to the location of a malignant mass in a mammogram in less than 2 seconds after image onset. Moreover, the longer they take to visually fixate the location of the mass, the less likely it is that they will report it. We conjectured that this behavior was due to the formation of the initial hypothesis about the image (i.e., 'normal' - no lesions to report, or 'abnormal' - possible lesions to report). This initial hypothesis is formed as a result of a difference template between the experts' expectations of the image and the actual image. Hence, when the image is displayed, the expert detects the areas that do not correspond to their 'a priori expectation', and these areas get assigned weights according to the magnitude of the perturbation. The radiologist then uses eye movements to guide the high resolution fovea to each of these locations, in order to resolve each perturbation. To accomplish this task successfully the radiologist uses not only the local features in the area but also lateral comparisons with selected background locations, and this comprises the radiologist's visual search strategy. Eye-position tracking studies seem to suggest that no two radiologists search the breast parenchyma alike, which makes one wonder whether successful search models can be developed. In this study we show that there is more to the experts' search strategy than meets the eye.

Mello-Thoms, Claudia

2008-04-01

354

Incorporating holistic visual search concepts into a SPECT myocardial perfusion imaging numerical observer  

NASA Astrophysics Data System (ADS)

Previous Single Photon Emission Computed Tomography (SPECT) myocardial perfusion imaging (MPI) research has explored the utility of numerical observers. One previous study proposed that the model of holistic visual search of a myocardial perfusion image by an expert human observer might improve the development of a SPECT MPI numerical observer. Further examination of numerical processing techniques that seem to be analogous to initial stage of human holistic image search has helped to further refine the numerical observer. The current numerical observer considers some fundamental issues in the refinement of the numerical observer: the need for background estimation, the determination of blobs and the 'search-like' selection of a few blobs for subsequent decision analysis.

O'Connor, J. Michael; Gifford, Howard C.; Brankov, Jovan G.; Pretorius, P. H.

2011-03-01

355

Digital Pattern Search and Its Hybridization with Genetic Algorithms for Bound Constrained Global Optimization  

NASA Astrophysics Data System (ADS)

In this paper, we present a recently developed pattern search method called Genetic Pattern Search algorithm (GPSA) for the global optimization of cost function subject to simple bounds. GPSA is a combined global optimization method using genetic algorithm (GA) and Digital Pattern Search (DPS) method, which has the digital structure represented by binary strings and guarantees convergence to stationary points from arbitrary starting points. The performance of GPSA is validated through extensive numerical experiments on a number of well known functions and on robot walking application. The optimization results confirm that GPSA is a robust and efficient global optimization method.

Kim, Nam-Geun; Park, Youngsu; Kim, Jong-Wook; Kim, Eunsu; Kim, Sang Woo

356

The role of the pulvinar in distractor processing and visual search.  

PubMed

The pulvinar nuclei of the thalamus are hypothesized to coordinate attentional selection in the visual cortex. Different models have, however, been proposed for the precise role of the pulvinar in attention. One proposal is that the pulvinar mediates shifts of spatial attention; a different proposal is that it serves the filtering of distractor information. At present, the relation between these possible operations and their relative importance in the pulvinar remains unresolved. We address this issue by contrasting these proposals in two fMRI experiments. We used a visual search paradigm that permitted us to dissociate neural activity reflecting shifts of attention from activity underlying distractor filtering. We find that distractor filtering, but not the operation of shifting attention, is associated with strong activity enhancements in dorsal and ventral regions of the pulvinar as well as in early visual cortex areas including the primary visual cortex. Our observations indicate that distractor filtering is the preponderant attentional operation subserved by the pulvinar, presumably mediated by a modulation of processing in visual areas where spatial resolution is sufficiently high to separate target from distractor input. PMID:22488931

Strumpf, Hendrick; Mangun, George R; Boehler, Carsten N; Stoppel, Christian; Schoenfeld, Mircea A; Heinze, Hans-Jochen; Hopf, Jens-Max

2012-04-04

357

Simulated pathline visualization of computed periodic blood flow patterns  

Microsoft Academic Search

Improvements in computer hardware and software have made it possible to model pulsatile blood flow in realistic arterial geometries. Such studies produce enormous amounts of velocity data, which are often difficult to interpret and communicate using traditional contour and\\/or vector field plots. Inspired by in vitro flow visualization techniques such as particle image velocimetry (PIV), we describe a simple and

David A. Steinman

2000-01-01

358

Use Patterns of Visual Cues in Computer-Mediated Communication  

ERIC Educational Resources Information Center

Communication in the virtual environment can be challenging for participants because it lacks physical presence and nonverbal elements. Participants may have difficulties expressing their intentions and emotions in a primarily text-based course. Therefore, the use of visual communication elements such as pictographic and typographic marks can be…

Bolliger, Doris U.

2009-01-01

359

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

360

Use Patterns of Visual Cues in Computer-Mediated Communication  

ERIC Educational Resources Information Center

|Communication in the virtual environment can be challenging for participants because it lacks physical presence and nonverbal elements. Participants may have difficulties expressing their intentions and emotions in a primarily text-based course. Therefore, the use of visual communication elements such as pictographic and typographic marks can be…

Bolliger, Doris U.

2009-01-01

361

Visualization of phase objects by the use of moiré patterns  

Microsoft Academic Search

A method closely related to phase object holography is described where the information is retrieved from the hologram itself and not from the reconstructed image: a two beam interference pattern is recorded on film. When a phase object is inserted in one of the beams and the film is exposed once more, a Moiré pattern appears, describing the object. A

J. Shamir

1972-01-01

362

Visualizing Long-Term Patterns of Water Temperature  

Microsoft Academic Search

Long-term patterns in river water temperature are relevant to questions pertaining to fish welfare and hydroelectric dam operations. Yet, in fish biology and watershed hydrology, the typical ways in which river water temperature data are displayed do not readily and easily show the long-term patterns in the data. We use different styles of displaying such data so that changes of

Ronald N. Kickert; Dennis D. Dauble

2002-01-01

363

Searching for Truth: Internet Search Patterns as a Method of Investigating Online Responses to a Russian Illicit Drug Policy Debate  

PubMed Central

Background This is a methodological study investigating the online responses to a national debate over an important health and social problem in Russia. Russia is the largest Internet market in Europe, exceeding Germany in the absolute number of users. However, Russia is unusual in that the main search provider is not Google, but Yandex. Objective This study had two main objectives. First, to validate Yandex search patterns against those provided by Google, and second, to test this method's adequacy for investigating online interest in a 2010 national debate over Russian illicit drug policy. We hoped to learn what search patterns and specific search terms could reveal about the relative importance and geographic distribution of interest in this debate. Methods A national drug debate, centering on the anti-drug campaigner Egor Bychkov, was one of the main Russian domestic news events of 2010. Public interest in this episode was accompanied by increased Internet search. First, we measured the search patterns for 13 search terms related to the Bychkov episode and concurrent domestic events by extracting data from Google Insights for Search (GIFS) and Yandex WordStat (YaW). We conducted Spearman Rank Correlation of GIFS and YaW search data series. Second, we coded all 420 primary posts from Bychkov's personal blog between March 2010 and March 2012 to identify the main themes. Third, we compared GIFS and Yandex policies concerning the public release of search volume data. Finally, we established the relationship between salient drug issues and the Bychkov episode. Results We found a consistent pattern of strong to moderate positive correlations between Google and Yandex for the terms "Egor Bychkov" (r s = 0.88, P < .001), “Bychkov” (r s = .78, P < .001) and “Khimki”(r s = 0.92, P < .001). Peak search volumes for the Bychkov episode were comparable to other prominent domestic political events during 2010. Monthly search counts were 146,689 for “Bychkov” and 48,084 for “Egor Bychkov”, compared to 53,403 for “Khimki” in Yandex. We found Google potentially provides timely search results, whereas Yandex provides more accurate geographic localization. The correlation was moderate to strong between search terms representing the Bychkov episode and terms representing salient drug issues in Yandex–“illicit drug treatment” (r s = .90, P < .001), "illicit drugs" (r s = .76, P < .001), and "drug addiction" (r s = .74, P < .001). Google correlations were weaker or absent–"illicit drug treatment" (r s = .12, P = .58), “illicit drugs ” (r s = -0.29, P = .17), and "drug addiction" (r s = .68, P < .001). Conclusions This study contributes to the methodological literature on the analysis of search patterns for public health. This paper investigated the relationship between Google and Yandex, and contributed to the broader methods literature by highlighting both the potential and limitations of these two search providers. We believe that Yandex Wordstat is a potentially valuable, and underused data source for researchers working on Russian-related illicit drug policy and other public health problems. The Russian Federation, with its large, geographically dispersed, and politically engaged online population presents unique opportunities for studying the evolving influence of the Internet on politics and policy, using low cost methods resilient against potential increases in censorship.

Gillespie, James A; Quinn, Casey

2012-01-01

364

Improving biomolecular pattern discovery and visualization with hybrid self-adaptive networks.  

PubMed

There is an increasing need to develop powerful techniques to improve biomedical pattern discovery and visualization. This paper presents an automated approach, based on hybrid self-adaptive neural networks, to pattern identification and visualization for biomolecular data. The methods are tested on two datasets: leukemia expression data and DNA splice-junction sequences. Several supervised and unsupervised models are implemented and compared. A comprehensive evaluation study of some of their intrinsic mechanisms is presented. The results suggest that these tools may be useful to support biological knowledge discovery based on advanced classification and visualization tasks. PMID:16689206

Wang, Haiying; Azuaje, Francisco; Black, Norman

2002-12-01

365

Pattern-based similarity search for microarray data  

Microsoft Academic Search

One fundamental task in near-neighbor search as well as other similarity matching efforts is to find a distance function that can efficiently quantify the similarity between two objects in a meaningful way. In DNA microarray analysis, the expression levels of two closely related genes may rise and fall synchronously in response to a set of experimental stimuli. Although the magnitude

Haixun Wang; Jian Pei; Philip S. Yu

2005-01-01

366

Visual search in ecological and non-ecological displays: evidence for a non-monotonic effect of complexity on performance.  

PubMed

Considerable research has been carried out on visual search, with single or multiple targets. However, most studies have used artificial stimuli with low ecological validity. In addition, little is known about the effects of target complexity and expertise in visual search. Here, we investigate visual search in three conditions of complexity (detecting a king, detecting a check, and detecting a checkmate) with chess players of two levels of expertise (novices and club players). Results show that the influence of target complexity depends on level of structure of the visual display. Different functional relationships were found between artificial (random chess positions) and ecologically valid (game positions) stimuli: With artificial, but not with ecologically valid stimuli, a "pop out" effect was present when a target was visually more complex than distractors but could be captured by a memory chunk. This suggests that caution should be exercised when generalising from experiments using artificial stimuli with low ecological validity to real-life stimuli. PMID:23320084

Chassy, Philippe; Gobet, Fernand

2013-01-08

367

Simulated pathline visualization of computed periodic blood flow patterns.  

PubMed

Improvements in computer hardware and software have made it possible to model pulsatile blood flow in realistic arterial geometries. Such studies produce enormous amounts of velocity data, which are often difficult to interpret and communicate using traditional contour and/or vector field plots. Inspired by in vitro flow visualization techniques such as particle image velocimetry (PIV), we describe a simple and effective method for visualizing periodic three-dimensional velocity data, based on the subdivision and sequential display of computed particle trajectories. Analogous to a PIV experiment, the length and spacing of such simulated particle pathlines are controlled by user-specified shutter-speed and frame rate variables. Strategies for color-coding pathlines to highlight important hemodynamic features such as recirculation zones and branch flow division are presented. PMID:10708784

Steinman, D A

2000-05-01

368

A sleep pattern analysis and visualization system to support people with early dementia  

Microsoft Academic Search

Sleep disturbances are among the most distressing of all Alzheimer's disease related symptoms. In some cases, however, the sleep disturbance may be a marker for early Alzheimer's disease. In this paper we present a sleep pattern detection and visualization system developed to support the monitoring of sleep patterns and assessment of sleep disturbances for people diagnosed with dementia, at the

Hoda Nikamalfard; Huiru Zheng; Haiying Wang; Maurice Mulvenna; Paul McCullagh; Paul Jeffers

2011-01-01

369

Identification of the ideal clutter metric to predict time dependence of human visual search  

NASA Astrophysics Data System (ADS)

The Army Night Vision and Electronic Sensors Directorate (NVESD) has recently performed a human perception experiment in which eye tracker measurements were made on trained military observers searching for targets in infrared images. This data offered an important opportunity to evaluate a new technique for search modeling. Following the approach taken by Jeff Nicoll, this model treats search as a random walk in which the observers are in one of two states until they quit: they are either searching, or they are wandering around looking for a point of interest. When wandering they skip rapidly from point to point. When examining they move more slowly, reflecting the fact that target discrimination requires additional thought processes. In this paper we simulate the random walk, using a clutter metric to assign relative attractiveness to points of interest within the image which are competing for the observer's attention. The NVESD data indicates that a number of standard clutter metrics are good estimators of the apportionment of observer's time between wandering and examining. Conversely, the apportionment of observer time spent wandering and examining could be used to reverse engineer the ideal clutter metric which would most perfectly describe the behavior of the group of observers. It may be possible to use this technique to design the optimal clutter metric to predict performance of visual search.

Cartier, Joan S.; Hsu, David H.

1995-05-01

370

Visual constraints in foraging bumblebees: Flower size and color affect search time and flight behavior  

PubMed Central

In optimal foraging theory, search time is a key variable defining the value of a prey type. But the sensory-perceptual processes that constrain the search for food have rarely been considered. Here we evaluate the flight behavior of bumblebees (Bombus terrestris) searching for artificial flowers of various sizes and colors. When flowers were large, search times correlated well with the color contrast of the targets with their green foliage-type background, as predicted by a model of color opponent coding using inputs from the bees' UV, blue, and green receptors. Targets that made poor color contrast with their backdrop, such as white, UV-reflecting ones, or red flowers, took longest to detect, even though brightness contrast with the background was pronounced. When searching for small targets, bees changed their strategy in several ways. They flew significantly slower and closer to the ground, so increasing the minimum detectable area subtended by an object on the ground. In addition, they used a different neuronal channel for flower detection. Instead of color contrast, they used only the green receptor signal for detection. We relate these findings to temporal and spatial limitations of different neuronal channels involved in stimulus detection and recognition. Thus, foraging speed may not be limited only by factors such as prey density, flight energetics, and scramble competition. Our results show that understanding the behavioral ecology of foraging can substantially gain from knowledge about mechanisms of visual information processing.

Spaethe, J.; Tautz, J.; Chittka, L.

2001-01-01

371

Age and distraction are determinants of performance on a novel visual search task in aged Beagle dogs  

Microsoft Academic Search

Aging has been shown to disrupt performance on tasks that require intact visual search and discrimination abilities in human\\u000a studies. The goal of the present study was to determine if canines show age-related decline in their ability to perform a\\u000a novel simultaneous visual search task. Three groups of canines were included: a young group (N?=?10; 3 to 4.5 years), an old

Shikha Snigdha; Lori-Ann Christie; Christina De Rivera; Joseph A. Araujo; Norton W. Milgram; Carl W. Cotman

372

Parietal substrates for dimensional effects in visual search: evidence from lesion-symptom mapping.  

PubMed

In visual search, the detection of pop-out targets is facilitated when the target-defining dimension remains the same compared with when it changes across trials. We tested the brain regions necessary for these dimensional carry-over effects using a voxel-based morphometry study with brain-lesioned patients. Participants had to search for targets defined by either their colour (red or blue) or orientation (right- or left-tilted), and the target dimension either stayed the same or changed on consecutive trials. Twenty-five patients were categorized according to whether they showed an effect of dimensional change on search or not. The two groups did not differ with regard to their performance on several working memory tasks, and the dimensional carry-over effects were not correlated with working memory performance. With spatial, sustained attention and working memory deficits as well as lesion volume controlled, damage within the right inferior parietal lobule (the angular and supramarginal gyri) extending into the intraparietal sulcus was associated with an absence of dimensional carry-over (P < 0.001, cluster-level corrected for multiple comparisons). The data suggest that these regions of parietal cortex are necessary to implement attention shifting in the context of visual dimensional change. PMID:23404335

Utz, Sandra; Humphreys, Glyn W; Chechlacz, Magdalena

2013-02-11

373

User-assisted visual search and tracking across distributed multi-camera networks  

NASA Astrophysics Data System (ADS)

Human CCTV operators face several challenges in their task which can lead to missed events, people or associations, including: (a) data overload in large distributed multi-camera environments; (b) short attention span; (c) limited knowledge of what to look for; and (d) lack of access to non-visual contextual intelligence to aid search. Developing a system to aid human operators and alleviate such burdens requires addressing the problem of automatic re-identification of people across disjoint camera views, a matching task made difficult by factors such as lighting, viewpoint and pose changes and for which absolute scoring approaches are not best suited. Accordingly, we describe a distributed multi-camera tracking (MCT) system to visually aid human operators in associating people and objects effectively over multiple disjoint camera views in a large public space. The system comprises three key novel components: (1) relative measures of ranking rather than absolute scoring to learn the best features for matching; (2) multi-camera behaviour profiling as higher-level knowledge to reduce the search space and increase the chance of finding correct matches; and (3) human-assisted data mining to interactively guide search and in the process recover missing detections and discover previously unknown associations. We provide an extensive evaluation of the greater effectiveness of the system as compared to existing approaches on industry-standard i-LIDS multi-camera data.

Raja, Yogesh; Gong, Shaogang; Xiang, Tao

2011-10-01

374

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

375

Measuring the impact of health policies using Internet search patterns: the case of abortion  

Microsoft Academic Search

BACKGROUND: Internet search patterns have emerged as a novel data source for monitoring infectious disease trends. We propose that these data can also be used more broadly to study the impact of health policies across different regions in a more efficient and timely manner. METHODS: As a test use case, we studied the relationships between abortion-related search volume, local abortion

Ben Y Reis; John S Brownstein

2010-01-01

376

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

377

Flow Visualization and Pattern Formation in Vertically Falling Liquid Films  

NASA Astrophysics Data System (ADS)

Analytical results of a low-dimensional two equation h-q model and results of a direct numerical simulation of the transient two-dimensional Navier Stokes equations are presented for vertically falling liquid films along a solid wall. The numerical study aims at the elucidation of the hydrodynamics of the falling film. The analytical study aims at the calculation of the parameter space where pattern formation occurs for this flow. It has been found that when the wave amplitude exceeds a certain magnitude, flow reversal occurs in the film underneath the minimum of the waves [1]. The instantaneous vortical structures possess two hyperbolic points on the vertical wall and an elliptic point in the film. As the wave amplitude increases further, the elliptic point reaches the free surface of the film and two more hyperbolic points are formed in the free surface that replace the elliptic point. Between the two hyperbolic points on the free surface, the streamwise component of velocity is negative and the film is divided into asymmetric patterns of up and down flows. Depending on the value of the Kapitza number, these patterns are either stationary or oscillatory. Physical reasons for the influence of the Kapitza number on pattern formation are given. Movies are shown where the pattern formation is demonstrated. [1] N.A.Malamataris and V.Balakotaiah (2008), AIChE J., 54(7), p. 1725-1740

Balakotaiah, Vemuri; Malamataris, Nikolaos

2008-11-01

378

Texture segregation and visual search: a comparison of the effects of random variations along irrelevant dimensions.  

PubMed

The effects of irrelevant variations in the color and depth of elements on participants' ability to detect and discriminate elements defined by a difference in orientation were compared. Consistent with previous research, it was found that there was no effect or small effects if the targets were single elements in visual search tasks and that there were large effects for targets defined by several elements defining an area in visual segmentation tasks. It is suggested that the reason for the discrepancy between the 2 paradigms lies in the need for grouping processes in segmentation experiments. This notion was examined in 3 additional experiments that manipulated grouping processes through task demands and stimulus design. The data provide tentative support for this notion. PMID:9778828

Snowden, R J

1998-10-01

379

Target-nontarget similarity modulates stimulus-driven control in visual search.  

PubMed

The literature contains conflicting results concerning whether an irrelevant featural singleton (an item unique with respect to a feature such as color or brightness) can control attention in a stimulus-driven manner. The present study explores whether target-nontarget similarity influences stimulus-driven shifts of attention to a distractor. An experiment evaluated whether manipulating target-nontarget similarity by varying orientation would modulate distraction by an irrelevant feature (a bright singleton). We found that increasing target-nontarget similarity resulted in a decreased impact of a uniquely bright object on visual search. This method of manipulating the target-nontarget similarity independent of the salience of a distracting feature suggests that the extent to which visual attention is stimulus-driven depends on the target-nontarget similarity. PMID:17048741

Proulx, Michael J; Egeth, Howard E

2006-06-01

380

Texture segmentation and visual search for pop-out targets. An ERP study.  

PubMed

"Parallel" visual search and effortless texture segmentation were believed to rely on similar mechanisms until Wolfe [Vis. Res. 32 (1992) 757] demonstrated that efficient visual search and effortless texture segmentation are not always the same thing. In a recent study, Meinecke and Donk [Perception 31 (2002) 591] varied display size in a pop-out task and found that, albeit stimulus elements and the task remained the same, different set sizes led to different processing modes. These findings indicate that it may suffice to vary set size in an otherwise unchanged pop-out task to initiate different processing which may be similar to the processing in efficient visual search and in effortless texture segmentation. In four experiments, we further investigated this issue by presenting stimulus arrays of different set sizes while recording event-related brain potentials (ERPs). We found that when display size was increased, detection performance first decreased slightly before it then increased. ERP effects were observed for the posterior N2 (N2p), the N2pc and the P3 component. All three components showed variations with set size; N2p differential amplitude effects were confined to large set sizes, whereas an N2pc was obtained for a broader set size range except for very small set sizes and the largest set size (121 elements). We interpret both the non-monotonic relationship between set size and response data and the variations of ERP components with set size as evidence in favor of different processing occurring for stimulus arrays with small and large set sizes. PMID:15511648

Schubö, Anna; Schröger, Erich; Meinecke, Cristina

2004-11-01

381

Attention changes perceived size of moving visual patterns.  

PubMed

Spatial attention shifts receptive fields in monkey extrastriate visual cortex toward the focus of attention (S. Ben Hamed, J. R. Duhamel, F. Bremmer, & W. Graf, 2002; C. E. Connor, J. L. Gallant, D. C. Preddie, & D. C. Van Essen, 1996; C. E. Connor, D. C. Preddie, J. L. Gallant, & D. C. Van Essen, 1997; T. Womelsdorf, K. Anton-Erxleben, F. Pieper, & S. Treue, 2006). This distortion in the retinotopic distribution of receptive fields might cause distortions in spatial perception such as an increase of the perceived size of attended stimuli. Here we test for such an effect in human subjects by measuring the point of subjective equality (PSE) for the perceived size of a neutral and an attended stimulus when drawing automatic attention to one of two spatial locations. We found a significant increase in perceived size of attended stimuli. Depending on the absolute stimulus size, this effect ranged from 4% to 12% and was more pronounced for smaller than for larger stimuli. In our experimental design, an attentional effect on task difficulty or a cue bias might influence the PSE measure. We performed control experiments and indeed found such effects, but they could only account for part of the observed results. Our findings demonstrate that the allocation of transient spatial attention onto a visual stimulus increases its perceived size and additionally biases subjects to select this stimulus for a perceptual judgment. PMID:17997660

Anton-Erxleben, Katharina; Henrich, Christian; Treue, Stefan

2007-08-23

382

Low target prevalence is a stubborn source of errors in visual search tasks.  

PubMed

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 characteristic of important search tasks such as airport security and medical screening where miss errors are dangerous. A series of experiments show this prevalence effect is very robust. In signal detection terms, the prevalence effect can be explained as a criterion shift and not a change in sensitivity. Several efforts to induce observers to adopt a better criterion fail. However, a regime of brief retraining periods with high prevalence and full feedback allows observers to hold a good criterion during periods of low prevalence with no feedback. PMID:17999575

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

2007-11-01

383

Visual search for oriented lines: the role of angular relations between targets and distractors.  

PubMed

Subjects can perform parallel visual search for an item of unique orientation when it is presented on a background texture composed of lines of two other orientations. A number of cues can be used to speed this search. It helps if the target has a unique categorical status (e.g., it is the only 'steep' item) (Wolfe et al., J. Exp. Psychol. Hum. Percept. Perf. 18, 34-49 1992). It helps if the two background orientations are symmetrical about a vertical axis (Wolfe and Friedman-Hill, Psychol. Sci. 3, 194-198, 1992). The experiments presented here show that it helps if the angles formed by the target with one of the distractor types are smaller than the angles formed by the two distractor orientations. These results illustrate that stimulus similarity is a complex concept even for a simple feature like orientation. PMID:1419930

Wolfe, J M; Friedman-Hill, S R

1992-01-01

384

Low target prevalence is a stubborn source of errors in visual search tasks  

PubMed Central

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 characteristic of important search tasks like airport security and medical screening where miss errors are dangerous. A series of experiments show this prevalence effect is very robust. In signal detection terms, the prevalence effect can be explained as a criterion shift and not a change in sensitivity. Several efforts to induce observers to adopt a better criterion fail. However, a regime of brief retraining periods with high prevalence and full feedback allows observers to hold a good criterion during periods of low prevalence with no feedback.

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

2009-01-01

385

Effects of Retinal Image Degradation on Pre-Attentive Visual Search (PAVS) Efficiency for Flicker, Movment and Orientation Stimuli  

Microsoft Academic Search

Background: Previous research has shown that several clinical conditions cause increased pre-attentive visual search (PAVS) times, implying reduced parallel search capabilities in glaucoma and DLB dementia. The purpose of the research reported here was to examine for the first time the resistance of PAVS to dioptric blur using targets differing from the background in terms of flicker, vertical displacement, and

Peter Davison; James Loughman

2006-01-01

386

Effect of skill level on recall of visually presented patterns of musical notes.  

PubMed

Expertise effects in music were studied in a new task: the construction of mental representations from separate fragments. Groups of expert musicians and non-musicians were asked to recall note patterns presented visually note by note. Skill-level, musical well-formedness of the note patterns and presentation mode were varied. The musicians recalled note patterns better than the non-musicians, even though the presentation was visual and successive. Furthermore, only musicians' performance was affected by musical well-formedness of the note patterns when visual gestalt properties, verbal rehearsability, and familiarity of the stimuli were controlled. Musicians were also able to use letter names referring to notes as efficiently as visual notes, which indicates that the better recall of musicians cannot be explained by perceptual visual chunking. These results and the effect of skill level on the distribution of recall errors indicate that the ability to chunk incoming information into meaningful units does not require that complete familiar patterns are accessible to encoding processes, yet previous knowledge stored in long-term memory affects representation construction in working memory. The present method offers a new reliable tool, and its implications to the research on construction of representations and musical imagery are discussed. PMID:17430362

Kalakoski, Virpi

2007-04-01

387

Teaching social competence: in search of design patterns  

Microsoft Academic Search

COSPATIAL is a multi-disciplinary project that is using collaborative virtual reality and tabletop devices for training social competence within the theoretical framework of Cognitive-Behavioral Therapy. Our ultimate objective is to create a set of patterns for designing applications in collaborative technologies that are suitable for children with autism as well as typically developing children. We describe the rationale for CBT-informed

Massimo Zancanaro; Eynat Gal; Sarah Parsons; Nirit Bauminger; Sue Cobb

2010-01-01

388

Structural search and retrieval using a tableau representation of protein folding patterns  

Microsoft Academic Search

Comparison and classification of folding patterns from a database of protein structures is crucial to understand the principles of pro- tein architecture, evolution and function. Current search methods for proteins with similar folding patterns are slow and computationally intensive. The sharp growth in the number of known protein structures poses severe challenges for methods of structural comparison. There is a

Arun Siddharth Konagurthu; Peter J. Stuckey; Arthur M. Lesk

2008-01-01

389

Patterns and Sequences of Multiple Query Reformulations in Web Searching: A Preliminary Study.  

ERIC Educational Resources Information Center

|Reports on patterns and sequences of query reformulation based on query logs from a Web search engine. Results show that while most query reformulation involves content changes, about 15% of reformulation is related to format modifications. Six patterns of query reformulation emerged as a result of sequence analysis: specified, parallel,…

Rieh, Soo Young; Xie, Hong

2001-01-01

390

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

391

Pattern recognition with the optic nerve visual prosthesis.  

PubMed

A volunteer with retinitis pigmentosa and no residual vision was chronically implanted with an optic nerve electrode connected to an implanted neurostimulator and antenna. An external controller with telemetry was used for electrical activation of the nerve which resulted in phosphene perception. Open-loop stimulation allowed the collection of phosphene attributes and the ability to elicit perception of simple geometrical patterns. Low perception thresholds allowed for large current intensity range within safety limits. In a closed-loop paradigm, the volunteer was using a head-worn video camera to explore a projection screen. The volunteer underwent performance evaluation during the course of a training program with 45 simple patterns. After learning, the volunteer reached a recognition score of 63% with a processing time of 60 s. Mean performance in orientation discrimination reached 100% with a processing time of 8 s. PMID:14616518

Veraart, Claude; Wanet-Defalque, Marie-Chantal; Gérard, Benoît; Vanlierde, Annick; Delbeke, Jean

2003-11-01

392

Effect of a Concurrent Auditory Task on Visual Search Performance in a Driving-Related Image-Flicker Task  

Microsoft Academic Search

The effect of a concurrent auditory task on visual search was investigated using an image-flicker technique. Participants were undergraduate university students with normal or corrected-to-normal vision who searched for changes in images of driving scenes that involved either driving-related (e.g., traffic light) or driving-unrelated (e.g., mailbox) scene elements. The results indicated that response times were significantly slower if the search

Christian M. Richard; Richard D. Wright; Cheryl Ee; Steven L. Prime; Yujiro Shimizu; John Vavrik

2002-01-01

393

Local binary pattern based texture analysis for visual fire recognition  

Microsoft Academic Search

Color and shape features have difficulty to recognize fire from fire-colored, irregular-shaped and moving objects. An effective algorithm using texture analysis with the Local Binary Pattern (LBP) is proposed in our paper to help deal with this problem. Besides grayscale and rotation invariance, the ability of LBP operator for multi-resolution analysis is enhanced through multiple LBP operators with varying parameters

Jing Huang; Jianhui Zhao; Weiwei Gao; Chengjiang Long; Lu Xiong; Zhiyong Yuan; Shizhong Han

2010-01-01

394

Pattern-reversal electroretinograms for the diagnosis and management of disorders of the anterior visual pathway.  

PubMed

The pattern electroretinogram is an electrophysiological test that assesses the function of inner retinal layers, particularly the ganglion cells layer of retina, using a reversing checkerboard or grating pattern that produces no change in average luminance over time. The normal pattern electroretinogram is composed of a proeminent positive component (P50) and a large later negative component (N95). Since structural damage that compromises the retinal ganglion cell layer can lead to pattern electroretinogram changes, particularly in the N95 amplitude, the test can be useful in the treatment of a number of anterior visual pathway diseases. In this article, we review the methods for recording pattern electroretinogram and its usefulness in the diagnosis and management of diseases including inflammatory, hereditary, ischemic and compressive lesions of the anterior visual pathway. PMID:21915454

Hokazono, Kenzo; Oyamada, Maria Kiyoko; Monteiro, Mário Luiz Ribeiro

395

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

396

Irrelevant relations and the active search for pattern structure in rat serial pattern learning.  

PubMed

Hersh (Mem Cogn 2:771-774, 1974) investigated the role of irrelevant relations in college students' pattern learning and performance for letter series completion problems. He created irrelevant relations in sequences by inserting items to make pattern structure ambiguous such that it was open to multiple interpretations during initial pattern processing. He reported irrelevant relations impaired humans' performance more when placed at the beginning of patterns than at the end. However, once pattern structure was induced, irrelevant relations were not impairing. Here, we examined the impact on rat serial pattern learning of irrelevant relations positioned at the beginning or end of a serial pattern. Rats pressed levers in a circular array according to the same structured serial pattern, 123 234 345 456 567, where digits indicated the clockwise position of the correct lever. This structured serial pattern was interleaved with repeating responses on lever 2 to produce irrelevant relations at the beginning of the pattern (Beginning: 122232 223242 324252 425262 526272), on lever 6 to produce irrelevant relations at the end of the pattern (End: 162636 263646 364656 465666 566676), or on lever 8 to produce no irrelevant relations (No Irrelevant Relations: 182838 283848 384858 485868 586878. Irrelevant relations significantly retarded learning regardless of their placement within the pattern. However, irrelevant relations retarded learning significantly more when placed at the pattern beginning versus end. The results indicate that rats, like humans, process patterns from beginning to end. PMID:21246231

Kundey, Shannon M A; Fountain, Stephen B

2011-01-19

397

Irrelevant relations and the active search for pattern structure in rat serial pattern learning  

PubMed Central

Hersh (Mem Cogn 2:771–774, 1974) investigated the role of irrelevant relations in college students’ pattern learning and performance for letter series completion problems. He created irrelevant relations in sequences by inserting items to make pattern structure ambiguous such that it was open to multiple interpretations during initial pattern processing. He reported irrelevant relations impaired humans’ performance more when placed at the beginning of patterns than at the end. However, once pattern structure was induced, irrelevant relations were not impairing. Here, we examined the impact on rat serial pattern learning of irrelevant relations positioned at the beginning or end of a serial pattern. Rats pressed levers in a circular array according to the same structured serial pattern, 123 234 345 456 567, where digits indicated the clockwise position of the correct lever. This structured serial pattern was interleaved with repeating responses on lever 2 to produce irrelevant relations at the beginning of the pattern (Beginning: 122232 223242 324252 425262 526272), on lever 6 to produce irrelevant relations at the end of the pattern (End: 162636 263646 364656 465666 566676), or on lever 8 to produce no irrelevant relations (No Irrelevant Relations: 182838 283848 384858 485868 586878. Irrelevant relations significantly retarded learning regardless of their placement within the pattern. However, irrelevant relations retarded learning significantly more when placed at the pattern beginning versus end. The results indicate that rats, like humans, process patterns from beginning to end.

Kundey, Shannon M. A.; Fountain, Stephen B.

2012-01-01

398

Generation of initial stepping pattern of a biped robot with modular dynamic encoding algorithm for searches  

NASA Astrophysics Data System (ADS)

In this paper, a modified version of dynamic encoding algorithm for searches (DEAS) is proposed and applied to generate walking patterns of a biped humanoid robot. For the controller of each joint motor to generate optimal trajectories, mDEAS is developed from the previous versions of exhaustive DEAS (eDEAS) and univariate DEAS (uDEAS). Modular DEAS (mDEAS) searches optimal coefficients of polynomials whose trajectories are assigned to joint motors. Since the number of the coefficients amounts up to 16, sharing search space and optimizing independently is expected to search efficiently. For validation of mDEAS, a simulation result about initial stepping is provided.

Kim, Taegyu; Kim, Jong-Wook

2007-12-01

399

Differential Expression Patterns of occ1- Related Genes in Adult Monkey Visual Cortex  

Microsoft Academic Search

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 ,a nocc1-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

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

2008-01-01

400

Retinocortical conduction time in diabetics with abnormal pattern reversal electroretinograms and visual evoked potentials  

Microsoft Academic Search

Clinically evident retinal vascular disease in patients with diabetes mellitus may be preceded by an increase in visual evoked potential latency in electrophysiologic testing. This increase may indicate either retinal or optic nerve dysfunction. To determine the origin of the latency increase we initiated a cross-sectional study of simultaneous pattern-reversal electroretinograms and visual evoked potentials. We recorded transient (3.8 reversals\\/second)

Gary L. Trick; Ronald M. Burde; Mae O. Gordon; Charles Kilo; Julio V. Santiago

1988-01-01

401

Beneficial effects of the NMDA antagonist ketamine on decision processes in visual search.  

PubMed

The ability of sensory-motor circuits to integrate sensory evidence over time is thought to underlie the process of decision-making in perceptual discrimination. Recent work has suggested that the NMDA receptor contributes to mediating neural activity integration. To test this hypothesis, we trained three female rhesus monkeys (Macaca mulatta) to perform a visual search task, in which they had to make a saccadic eye movement to the location of a target stimulus presented among distracter stimuli of lower luminance. We manipulated NMDA-receptor function by administering an intramuscular injection of the noncompetitive NMDA antagonist ketamine and assessed visual search performance before and after manipulation. Ketamine was found to lengthen response latency in a dose-dependent fashion. Surprisingly, it was also observed that response accuracy was significantly improved when lower doses were administered. These findings suggest that NMDA receptors play a crucial role in the process of decision-making in perceptual discrimination. They also further support the idea that multiple neural representations compete with one another through mutual inhibition, which may explain the speed-accuracy trade-off rule that shapes discrimination behavior: lengthening integration time helps resolve small differences between choice alternatives, thereby improving accuracy. PMID:20660277

Shen, Kelly; Kalwarowsky, Sarah; Clarence, Wendy; Brunamonti, Emiliano; Paré, Martin

2010-07-21

402

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

403

Visual evoked electrical and magnetic response to half-field stimulation using pattern reversal stimulation.  

PubMed

The visual evoked magnetic response to half-field stimulation using pattern reversal was studied using a d.c. SQUID coupled to a second order gradiometer. The main component of the magnetic response consisted of a positive wave at around 100 ms (P100M). At the time this component was present the response to half-field stimulation consisted of an outgoing magnetic field contralateral and extending to the midline. When the left half field was stimulated the outgoing field was over the posterior right visual cortex and when the right half field was stimulated it was over the left anterior visual cortex. These findings would correctly identify a source located in the contralateral visual cortex. The orientation of the dipoles was not that previously assumed to explain the paradoxical lateralization of the visual evoked potential. The results are discussed in terms of both electrical and magnetic models of the calcarine fissure. PMID:1408167

Harding, G F; Armstrong, R A; Janday, B

1992-04-01

404

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

405

Pattern of visual field defects in normal-tension and high-tension glaucoma.  

PubMed

There are probably two major types of causative factors in open-angle glaucoma: pressure-dependent and pressure-independent. If clinical features such as the pattern of visual field defects differ between normal-tension and high-tension glaucoma, the differences may provide an insight for discriminating between the pressure-dependent and the pressure-independent damage in open-angle glaucoma. This article gives a brief review of the most recent studies including reports wherein progression or pattern of visual field defects in normal-tension and high-tension glaucoma or primary open-angle glaucoma are addressed. Further deterioration of the visual field in 5 years is expected in about 50% of eyes with normal-tension glaucoma in which intraocular pressure is one of the contributing factors. This figure may be greater than that seen in eyes with primary open-angle glaucoma where intraocular pressure is controlled with surgery in the middle teens. When eyes with normal-tension glaucoma and high-tension glaucoma or primary open-angle glaucoma were matched for extent of overall visual field loss, many studies noted a difference in the pattern of visual field defects between the two groups. Visual field defects in normal-tension glaucoma are relatively more localized and closer to fixation, especially in the nasal superior quadrant and may be more predominant in the lower hemifield. Results of other psychophysical tests also appear to support the above findings. PMID:10150856

Araie, M

1995-04-01

406

Optimised autonomous search pattern evaluation using the Cerberus framework  

NASA Astrophysics Data System (ADS)

There is an increasing emphasis on the intelligent use of multiple sensor assets within military applications which is driven by a number of factors. Firstly, the deployment of multiple, co-operative sensors can provide a much greater situational awareness which is a key factor in military decision making at both strategic and tactical levels. Secondly, through careful and timely asset management, military tempo and effectiveness can be maintained and even enhanced such that the mission objectives are optimally prosecuted. Thirdly, intrinsic limitations of individual sensors and their processing demands can be reduced or even eliminated. From a mission perspective, this renders the constraints and frailties of the associated with the sensor network transparent to the military end users. Underpinning all of these factors is the need to adaptively control and manipulate the various sensor search vectors in both space and time. Such a design and operational capability is provided through Cerberus, an advanced design tool developed by Waterfall Solutions Ltd. Within this paper, investigations into a range of different military applications using the Cerberus design environment are reported and assessed in terms of the associated military objectives. These applications include the use of both manned and uninhabited air vehicles as well as land and sea based sensor platforms. The use and benefits of available a priori knowledge such as digital terrain data and mission intelligence can also be exploited within the Cerberus environment to great military advantage.

Angell, C.; Bernhardt, M.

2008-05-01

407

Model of visual contrast gain control and pattern masking.  

PubMed

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. PMID:9291608

Watson, A B; Solomon, J A

1997-09-01

408

Beam angle optimization for intensity-modulated radiation therapy using a guided pattern search method.  

PubMed

Generally, the inverse planning of radiation therapy consists mainly of the fluence optimization. The beam angle optimization (BAO) in intensity-modulated radiation therapy (IMRT) consists of selecting appropriate radiation incidence directions and may influence the quality of the IMRT plans, both to enhance better organ sparing and to improve tumor coverage. However, in clinical practice, most of the time, beam directions continue to be manually selected by the treatment planner without objective and rigorous criteria. The goal of this paper is to introduce a novel approach that uses beam's-eye-view dose ray tracing metrics within a pattern search method framework in the optimization of the highly non-convex BAO problem. Pattern search methods are derivative-free optimization methods that require a few function evaluations to progress and converge and have the ability to better avoid local entrapment. The pattern search method framework is composed of a search step and a poll step at each iteration. The poll step performs a local search in a mesh neighborhood and ensures the convergence to a local minimizer or stationary point. The search step provides the flexibility for a global search since it allows searches away from the neighborhood of the current iterate. Beam's-eye-view dose metrics assign a score to each radiation beam direction and can be used within the pattern search framework furnishing a priori knowledge of the problem so that directions with larger dosimetric scores are tested first. A set of clinical cases of head-and-neck tumors treated at the Portuguese Institute of Oncology of Coimbra is used to discuss the potential of this approach in the optimization of the BAO problem. PMID:23574810

Rocha, Humberto; Dias, Joana M; Ferreira, Brígida C; Lopes, Maria C

2013-04-11

409

Both egocentric and allocentric cues support spatial priming in visual search.  

PubMed

The perception-action model proposes that vision for perception and vision for action are subserved by two separate cortical systems, the ventral and dorsal streams, respectively [Milner, A. D., & Goodale, M. A. (1995). The visual brain in action (1st ed.). Oxford: Oxford University Press; Milner, A. D., & Goodale, M. A. (2006). The visual brain in action (2nd ed.). Oxford: Oxford University Press Inc.]. The dorsal stream codes spatial information egocentrically, that is, relative to the observer. Egocentric representations are argued to be highly transient; therefore, it might be expected that egocentric information cannot be used for spatial memory tasks, even when the visual information only needs to be retained for a few seconds. Here, by applying a spatial priming paradigm to a visual search task, we investigated whether short-term spatial memory can use egocentric information. Spatial priming manifests itself in speeded detection times for a target when that target appears in the same location it previously appeared in. Target locations can be defined in either egocentric or allocentric (i.e. relative to other items in the display) frames of reference; however, it is unclear which of these are used in spatial priming, or if both are. Our results show that both allocentric and egocentric cues were used in spatial priming, and that egocentric cues were in fact more effective than allocentric cues for short-term priming. We conclude that egocentric information can persist for several seconds; a conclusion which is at odds with the assumption of the perception-action model that egocentric representations are highly transient. PMID:19084545

Ball, Keira; Smith, Daniel; Ellison, Amanda; Schenk, Thomas

2008-11-24

410

Incidental learning speeds visual search by lowering response thresholds, not by improving efficiency: Evidence from eye movements  

PubMed Central

When observers search for a target object, they incidentally learn the identities and locations of “background” objects in the same display. This learning can facilitate search performance, eliciting faster reaction times for repeated displays (Hout & Goldinger, 2010). Despite these findings, visual search has been successfully modeled using architectures that maintain no history of attentional deployments; they are amnesic (e.g., Guided Search Theory; Wolfe, 2007). In the current study, we asked two questions: 1) under what conditions does such incidental learning occur? And 2) what does viewing behavior reveal about the efficiency of attentional deployments over time? In two experiments, we tracked eye movements during repeated visual search, and we tested incidental memory for repeated non-target objects. Across conditions, the consistency of search sets and spatial layouts were manipulated to assess their respective contributions to learning. Using viewing behavior, we contrasted three potential accounts for faster searching with experience. The results indicate that learning does not result in faster object identification or greater search efficiency. Instead, familiar search arrays appear to allow faster resolution of search decisions, whether targets are present or absent.

Hout, Michael C.; Goldinger, Stephen D.

2011-01-01

411

Search of Possible Triggered Seismicity Patterns of Northern Tien Shan  

NASA Astrophysics Data System (ADS)

Statistical analysis of the Northern Tien Shan seismicity was performed considering the possible triggering impacts of natural and man-made mechanical and electromagnetic factors on seismic activity. Strong distant earthquakes, lunar-solar tides, and magnetic storms are considered as natural triggering factors. The man-made factors include underground nuclear explosions (UNE) and electromagnetic impacts provided by high-power magnetohydrodynamic pulsed (MHD) generators. The representative local earthquake catalog of the region under study (41°-46° N, 74°-82° E) includes 15577 events of M>1.67 from 1975 to 2000. Within this time period 330 UNE and 109 firing runs of MHD generators, which are considered as the possible man-made earthquake triggering factors, have been performed within or adjacent to the analyzed region. Various statistical methods (cross-correlation, spectral analysis, RTL-analysis, etc.) were employed. For the used statement of problem and applied initial data the statistically significant patterns of triggered seismicity of the Northern Tien-Shan due to impacts of UNE and MHD generators were not found. Large common periods of seismicity variation for time series of distant strong earthquakes and local seismic events were selected. There is significant number of common periods (7, 9, 14, 28, 186, and 16384 days) for variation of z-component of the earth tide and release of seismic energy that may point to an influence of the earth tides on the local seismicity.

Novikov, V.; Vorontsova, E.

2007-12-01

412

Flexible Feature-Based Inhibition in Visual Search Mediates Magnified Impairments of Selection: Evidence from Carry-Over Effects under Dynamic Preview-Search Conditions  

ERIC Educational Resources Information Center

|Evidence for inhibitory processes in visual search comes from studies using preview conditions, where responses to new targets are delayed if they carry a featural attribute belonging to the old distractor items that are currently being ignored--the negative carry-over effect (Braithwaite, Humphreys, & Hodsoll, 2003). We examined whether…

Andrews, Lucy S.; Watson, Derrick G.; Humphreys, Glyn W.; Braithwaite, Jason J.

2011-01-01

413

Functional connectivity for an "island of sparing" in autism spectrum disorder: an fMRI study of visual search.  

PubMed

Although autism is usually characterized with respect to sociocommunicative impairments, visual search is known as a domain of relative performance strength in this disorder. This study used functional MRI during visual search in children with autism spectrum disorder (n = 19; mean age = 13;10) and matched typically developing children (n = 19; mean age = 14;0). We selected regions of interest within two attentional networks known to play a crucial role in visual search processes, such as goal-directed selective attention, filtering of irrelevant distractors, and detection of behaviorally-relevant information, and examined activation and connectivity within and between these attentional networks. Additionally, based on prior research suggesting links between visual search abilities and autism symptomatology, we tested for correlations between sociocommunicative impairments and behavioral and neural indices of search. Contrary to many previous functional connectivity magnetic resonance imaging studies of autism that reported functional underconnectivity for task domains of weakness, we found atypically increased connectivity within and between attentional networks in autism. Additionally, we found increased functional connectivity for occipital regions, both locally and for long-distance connections with frontal regions. Both behavioral and neural indices of search were correlated with sociocommunicative impairment in children with autism. This association suggests that strengths in nonsocial visuospatial processing may be related to the development of core autistic sociocommunicative impairments. PMID:22495745

Keehn, Brandon; Shih, Patricia; Brenner, Laurie A; Townsend, Jeanne; Müller, Ralph-Axel

2012-04-12

414

Irrelevant relations and the active search for pattern structure in rat serial pattern learning  

Microsoft Academic Search

Hersh (Mem Cogn 2:771–774, 1974) investigated the role of irrelevant relations in college students’ pattern learning and performance for letter series completion\\u000a problems. He created irrelevant relations in sequences by inserting items to make pattern structure ambiguous such that it\\u000a was open to multiple interpretations during initial pattern processing. He reported irrelevant relations impaired humans’\\u000a performance more when placed at

Shannon M. A. Kundey; Stephen B. Fountain

2011-01-01

415

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

416

How patterns of bleached rods and cones become visual perceptual experiences: A proposal  

PubMed Central

In an attempt to increase information about how mammalian visual systems create a perceptual experience out of a retinal photochemical bleach pattern, this article brings together recent rat physiological data acquired with large electrodes, an old cat behavioral experiment, and two complex human behaviors: reading and the reversible blindness people experience when the scene being viewed is stabilized on the retinal surface. The outcome suggests this juxtaposition of disparate data sets has been logical, reasonable, and informative. The link between rats and reading is the fact that both rat and human retinas convert bleach patterns into ganglion cell volleys 3 times a second. The probable trigger for these episodic retinal volleys is a more or less abrupt change in the pattern of bleached rods and cones, and we claim the absence of this trigger when the image is stabilized is responsible for the blindness. The cat behavioral experiment correlates performance on visual discrimination tasks with the number of nerve fibers remaining after lesions of the optic tract. The analysis of the result, which shows that as few as 2% of the normal number of nerve fibers supports perfect performance of such tasks, prompts the concept of a second dynamic visual system, operating in parallel with the anatomical nervous system pictured in the textbooks. The dynamic visual system model, which brings into the foreground important old facts that have been neglected and integrates them with new data, offers a synthesis that may be useful in interpreting classical visual behavioral phenomena.

Galambos, Robert; Juhasz, Gabor

2001-01-01

417

Visualization of Flow Patterns in the Bonneville 2nd Powerhouse Forebay  

SciTech Connect

Three-dimensional (3D) computational fluid dynamics (CFD) models are increasingly being used to study forebay and tailrace flow systems associated with hydroelectric projects. This paper describes the fundamentals of creating effective 3D data visualizations from CFD model results using a case study from the Bonneville Dam. These visualizations enhance the utility of CFD models by helping the researcher and end user better understand the model results. To develop visualizations for the Bonneville Dam forebay model, we used specialized, but commonly available software and a standard high-end microprocessor workstation. With these tools we were able to compare flow patterns among several operational scenarios by producing a variety of contour, vector, stream-trace, and vortex-core plots. The differences in flow patterns we observed could impact efforts to divert downstream-migrating fish around powerhouse turbines.

Serkowski, John A.; Rakowski, Cynthia L.; Ebner, Laurie L.

2002-12-31

418

On Assisting a Visual-Facial Affect Recognition System with Keyboard-Stroke Pattern Information  

NASA Astrophysics Data System (ADS)

Towards realizing a multimodal affect recognition system, we are considering the advantages of assisting a visual-facial expression recognition system with keyboard-stroke pattern information. Our work is based on the assumption that the visual-facial and keyboard modalities are complementary to each other and that their combination can significantly improve the accuracy in affective user models. Specifically, we present and discuss the development and evaluation process of two corresponding affect recognition subsystems, with emphasis on the recognition of 6 basic emotional states, namely happiness, sadness, surprise, anger and disgust as well as the emotion-less state which we refer to as neutral. We find that emotion recognition by the visual-facial modality can be aided greatly by keyboard-stroke pattern information and the combination of the two modalities can lead to better results towards building a multimodal affect recognition system.

Stathopoulou, I.-O.; Alepis, E.; Tsihrintzis, G. A.; Virvou, M.

419

Visual scanning patterns and executive function in relation to facial emotion recognition in aging  

Microsoft Academic Search

Objective: The ability to perceive facial emotion varies with age. Relative to younger adults (YA), older adults (OA) are less accurate at identifying fear, anger, and sadness, and more accurate at identifying disgust. Because different emotions are conveyed by different parts of the face, changes in visual scanning patterns may account for age-related variability. We investigated the relation between scanning

Karishma S. Circelli; Uraina S. Clark; Alice Cronin-Golomb

2012-01-01

420

On the Possibility of Automatically Recognizing Certain Visual Patterns (Vozmozhnosti Avtomaticheskogo Raspoznavaniya Nekotorykh Vizualnykh Obrazov).  

National Technical Information Service (NTIS)

The report states that the recognition of such visual recognition objects as human faces can play some role in problems of automatic pattern recognition, in spite of the apparent complexity of the recognition of faces as compared, for example, with recogn...

G. S. Ramishvili

1967-01-01

421

Spatial patterns of visual cortical fast EEG during conditioned reflex in a rhesus monkey  

Microsoft Academic Search

A preliminary assay was made of the existence of time-space coherence patterns of fast EEG activity in the visual cortex of a Rhe- sus monkey. The primary intent of the present study was to evaluate the similarities and differences in relation to the olfactorybutb. where such eoherences have been described and have been demonstrated to be associated with behaviour. Segments

Walter J. Freeman; B VANDIJK

1987-01-01

422

Nurses' Behaviors and Visual Scanning Patterns May Reduce Patient Identification Errors  

Microsoft Academic Search

Patient identification (ID) errors occurring during the medication administration process can be fatal. The aim of this study is to determine whether differences in nurses' behaviors and visual scanning patterns during the medication administration process influence their capacities to identify patient ID errors. Nurse participants (n = 20) administered medications to 3 patients in a simulated clinical setting, with 1

Jenna L. Marquard; Philip L. Henneman; Ze He; Junghee Jo; Donald L. Fisher; Elizabeth A. Henneman

2011-01-01

423

Using Interactive Visualizations of WWW Log Data To Characterize Access Patterns and Inform Site Design.  

ERIC Educational Resources Information Center

|Discusses the use of Web log analysis to help understand user visit patterns to Web sites and describes the use of computer software to generate a variety of interactive visualizations of log data that can be used to explore server data across various dimensions. Explores difficulties of data collection, presentation, and interpretation.…

Hochheiser, Harry; Shneiderman, Ben

2001-01-01

424

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

425

An integrative and interactive framework for improving biomedical pattern discovery and visualization  

Microsoft Academic Search

Recent progress in medical sciences has led to an explosive growth of data. Due to its inherent complexity and diversity, mining such volumes of data to extract relevant knowledge represents an enormous challenge and opportunity. Interactive pattern discovery and visualization systems for biomedical data mining have received relatively little attention. Emphasis has been traditionally placed on automation and supervised classification

Haiying Wang; Francisco Azuaje; Norman D. Black

2004-01-01

426

Nurses' Behaviors and Visual Scanning Patterns May Reduce Patient Identification Errors  

ERIC Educational Resources Information Center

|Patient identification (ID) errors occurring during the medication administration process can be fatal. The aim of this study is to determine whether differences in nurses' behaviors and visual scanning patterns during the medication administration process influence their capacities to identify patient ID errors. Nurse participants (n = 20)…

Marquard, Jenna L.; Henneman, Philip L.; He, Ze; Jo, Junghee; Fisher, Donald L.; Henneman, Elizabeth A.

2011-01-01

427

Action Patterns for the Incremental Specification of the Execution Semantics of Visual Languages  

Microsoft Academic Search

We present a new approach - based on graph transformation - to incremental specification of the operational (execution) semantics of visual languages. The approach combines editing rules with two meta-models: one to define the concrete syntax and one for the static semantics. We introduce the notion of action patterns, defining basic actions (e.g. consuming or producing a token in transition-based

Paolo Bottoni; Juan de Lara; E. Guerra

2007-01-01

428

Flexibility and Coordination among Acts of Visualization and Analysis in a Pattern Generalization Activity  

ERIC Educational Resources Information Center

|This study aims at exploring processes of flexibility and coordination among acts of visualization and analysis in students' attempt to reach a general formula for a three-dimensional pattern generalizing task. The investigation draws on a case-study analysis of two 15-year-old girls working together on a task in which they are asked to calculate…

Nilsson, Per; Juter, Kristina

2011-01-01

429

Nurses' Behaviors and Visual Scanning Patterns May Reduce Patient Identification Errors  

ERIC Educational Resources Information Center

Patient identification (ID) errors occurring during the medication administration process can be fatal. The aim of this study is to determine whether differences in nurses' behaviors and visual scanning patterns during the medication administration process influence their capacities to identify patient ID errors. Nurse participants (n = 20)…

Marquard, Jenna L.; Henneman, Philip L.; He, Ze; Jo, Junghee; Fisher, Donald L.; Henneman, Elizabeth A.

2011-01-01

430

Cognitive Neuropsychology: Patterns of Co-occurrence Among the Associative Agnosias: Implications for Visual Object Representation  

Microsoft Academic Search

The patterns of co-occurrence among associative agnosia for faces, words and other objects are analysed and found to be consistent with the existence of two, rather than three, underlying visual recognition capacities. Different degrees and combinations of damage to these two capacities can account for the five different combinations of word, face, and object agnosia that are found, as well

Martha J. Farah

1991-01-01

431

Prognostic significance of the pattern visual evoked potential in ocular hypertension  

Microsoft Academic Search

This paper reports a prospective study on 49 ocular hypertensive patients to evaluate the prognostic significance of transient abnormalities in the pattern visual evoked potential (VEP) in the development of glaucoma. Seven of 24 patients with VEP abnormalities at diagnosis of ocular hypertension developed glaucomatous field defects in the follow-up period as compared with none of 25 patients with normal

L C Bray; K W Mitchell; J W Howe

1991-01-01

432

Two-Phase Pattern Search-based Learning Method for Multi-layer Neural Network  

NASA Astrophysics Data System (ADS)

A new multi-layer artificial neural network learning algorithm based on pattern search method is proposed. The learning model has two phases-a pattern search phase, and a local minimum-escaping phase. In the pattern search phase, our method performs local search iteratively and minimize the error measure function along with the set of descent directions of the error measure directly and finds the nearest minima efficiently. When the network gets stuck in local minima, the local minimum-escaping phase attempts to fill up the valley by modifying temperature parameters in ascent direction of the error measure. Thus, the two phases are repeated until the network gets out of local minima. The learning model is designed to provide a very simple and effective means of searching the minima of objective function directly without any knowledge of its derivatives. We test this algorithm on benchmark problems, such as exclusive-or (XOR), parity, Arabic numerals recognition, function approximation problems and a real world classification task. For all problems, the systems are shown be trained efficiently by our method. As a simple direct search method, it can be applied in hardware implementations easily.

Wang, Xugang; Tang, Zheng; Tamura, Hiroki; Ishii, Masahiro

433

Visual map development depends on the temporal pattern of binocular activity in mice.  

PubMed

Binocular competition is thought to drive eye-specific segregation in the developing visual system, potentially through Hebbian synaptic learning rules that are sensitive to correlations in afferent activity. Altering retinal activity can disrupt eye-specific segregation, but little is known about the temporal features of binocular activity that modulate visual map development. We used optogenetic techniques to directly manipulate retinal activity in vivo and identified a critical period before eye opening in mice when specific binocular features of retinal activity drive visual map development. Synchronous activation of both eyes disrupted segregation, whereas asynchronous stimulation enhanced segregation. The optogenetic stimulus applied was spatially homogenous; accordingly, retinotopy of ipsilateral projections was markedly perturbed, but contralateral retinotopy was unaffected or even improved. These results provide direct evidence that the synchrony and precise temporal pattern of binocular retinal activity during a critical period in development regulates eye-specific segregation and retinotopy in the developing visual system. PMID:22179110

Zhang, Jiayi; Ackman, James B; Xu, Hong-Ping; Crair, Michael C

2011-11-18

434

Been There, Seen That: A Neural Mechanism for Performing Efficient Visual Search  

PubMed Central

In everyday life, we efficiently find objects in the world by moving our gaze from one location to another. The efficiency of this process is brought about by ignoring items that are dissimilar to the target and remembering which target-like items have already been examined. We trained two animals on a visual foraging task in which they had to find a reward-loaded target among five task-irrelevant distractors and five potential targets. We found that both animals performed the task efficiently, ignoring the distractors and rarely examining a particular target twice. We recorded the single unit activity of 54 neurons in the lateral intraparietal area (LIP) while the animals performed the task. The responses of the neurons differentiated between targets and distractors throughout the trial. Further, the responses marked off targets that had been fixated by a reduction in activity. This reduction acted like inhibition of return in saliency map models; items that had been fixated would no longer be represented by high enough activity to draw an eye movement. This reduction could also be seen as a correlate of reward expectancy; after a target had been identified as not containing the reward the activity was reduced. Within a trial, responses to the remaining targets did not increase as they became more likely to yield a result, suggesting that only activity related to an event is updated on a moment-by-moment bases. Together, our data show that all the neural activity required to guide efficient search is present in LIP. Because LIP activity is known to correlate with saccade goal selection, we propose that LIP plays a significant role in the guidance of efficient visual search.

Arcizet, Fabrice; Ong, Wei Song; Bisley, James W.

2009-01-01

435

Efficiency of visual time-sharing behavior: the effects of menu structure on POI search tasks while driving  

Microsoft Academic Search

In this paper, the effects of two user interface menu structures on a mobile device display, list and grid, are compared in a driving simulation with the measures of visual time-sharing efficiency, visual load, driving performance and secondary task performance. Eighteen participants conducted a set of eight Point-of-Interest (POI) search tasks with the grid- or list-style menus on navigation software

Tuomo Kujala

2009-01-01

436

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

437

Sequence of pattern onset responses in the human visual areas: an fMRI constrained VEP source analysis  

Microsoft Academic Search

We measured the timing of activity in distinct functional areas of the human visual cortex after onset of a visual pattern. This is not possible with visual evoked potentials (VEPs) or magnetic fields alone, and direct combination of functional magnetic resonance imaging (fMRI) with electromagnetic data has turned out to be difficult. We tested a relatively new approach, where both

S. Vanni; J. Warnking; M. Dojat; C. Delon-Martin; J. Bullier; C. Segebarthb

2004-01-01

438

Child Looking Patterns: A Sudden Change in Visual Information Pick-Up at 32 Month of Age.  

ERIC Educational Resources Information Center

|This study examined infants' change in visual information pick-up, from an infant-like stimulus-locked visual scanning pattern to an adult-like cognitive control of visual information pick-up. Subjects were 21 children between 25 and 42 months of age. Eye movements were videotaped in a preferential looking situation and later analyzed as still…

Jacobsen, Karl; And Others

439

Multiscale pattern analysis of orientation-selective activity in the primary visual cortex  

PubMed Central

Although orientation columns are less than a millimeter in width, recent neuroimaging studies indicate that viewed orientations can be decoded from cortical activity patterns sampled at relatively coarse resolutions of several millimeters. One proposal is that these differential signals arise from random spatial irregularities in the columnar map. However, direct support for this hypothesis has yet to be obtained. Here, we used high-field, high-resolution functional magnetic resonance imaging (fMRI) and multivariate pattern analysis to determine the spatial scales at which orientation-selective information can be found in the primary visual cortex (V1) of cats and humans. We applied a multiscale pattern analysis approach in which fine- and coarse-scale signals were first removed by ideal spatial lowpass and highpass filters, and the residual activity patterns then analyzed by linear classifiers. Cat visual cortex, imaged at 0.3125mm resolution, showed a strong orientation signal at the scale of individual columns. Nonetheless, reliable orientation bias could still be found at spatial scales of several millimeters. In the human visual cortex, imaged at 1mm resolution, a majority of orientation information was found on scales of millimeters, with small contributions from global spatial biases exceeding ~1cm. Our high-resolution imaging results demonstrate a reliable millimeters-scale orientation signal, likely emerging from irregular spatial arrangements of orientation columns and their supporting vasculature. fMRI pattern analysis methods are thus likely to be sensitive to signals originating from other irregular columnar structures elsewhere in the brain.

Swisher, Jascha D.; Gatenby, J. Christopher; Gore, John C.; Wolfe, Benjamin A.; Moon, Chan-Hong; Kim, Seong-Gi; Tong, Frank

2010-01-01

440

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

441

Here Today, Gone Tomorrow - Adaptation to Change in Memory-Guided Visual Search  

PubMed Central

Visual search for a target object can be facilitated by the repeated presentation of an invariant configuration of nontargets (‘contextual cueing’). Here, we tested adaptation of learned contextual associations after a sudden, but permanent, relocation of the target. After an initial learning phase targets were relocated within their invariant contexts and repeatedly presented at new locations, before they returned to the initial locations. Contextual cueing for relocated targets was neither observed after numerous presentations nor after insertion of an overnight break. Further experiments investigated whether learning of additional, previously unseen context-target configurations is comparable to adaptation of existing contextual associations to change. In contrast to