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Sample records for reference visual field

  1. Visual field

    MedlinePlus

    Perimetry; Tangent screen exam; Automated perimetry exam; Goldmann visual field exam; Humphrey visual field exam ... Confrontation visual field exam : This is a quick and basic check of the visual field. The health care provider sits directly in front ...

  2. Visual field

    MedlinePlus

    Perimetry; Tangent screen exam; Automated perimetry exam; Goldmann visual field exam; Humphrey visual field exam ... Confrontation visual field exam : This is a quick and basic check of the visual field. The health care provider ...

  3. Visual field asymmetries in visual evoked responses

    PubMed Central

    Hagler, Donald J.

    2014-01-01

    Behavioral responses to visual stimuli exhibit visual field asymmetries, but cortical folding and the close proximity of visual cortical areas make electrophysiological comparisons between different stimulus locations problematic. Retinotopy-constrained source estimation (RCSE) uses distributed dipole models simultaneously constrained by multiple stimulus locations to provide separation between individual visual areas that is not possible with conventional source estimation methods. Magnetoencephalography and RCSE were used to estimate time courses of activity in V1, V2, V3, and V3A. Responses to left and right hemifield stimuli were not significantly different. Peak latencies for peripheral stimuli were significantly shorter than those for perifoveal stimuli in V1, V2, and V3A, likely related to the greater proportion of magnocellular input to V1 in the periphery. Consistent with previous results, sensor magnitudes for lower field stimuli were about twice as large as for upper field, which is only partially explained by the proximity to sensors for lower field cortical sources in V1, V2, and V3. V3A exhibited both latency and amplitude differences for upper and lower field responses. There were no differences for V3, consistent with previous suggestions that dorsal and ventral V3 are two halves of a single visual area, rather than distinct areas V3 and VP. PMID:25527151

  4. Global reference analysis and visualization environment (GRAVE)

    NASA Astrophysics Data System (ADS)

    Rodgers, Todd K.; Cochand, Jeffrey A.; Sivak, Joseph A.

    1993-03-01

    The Global Reference Analysis and Visualization Environment (GRAVE) is a research prototype multimedia system that manages a diverse variety of data types and presents them to the user in a format that is geographically referenced ton the surface of a globe. When the user interacts with the globe, the system automatically manages the `level-of-detail' issues to support these user actions (allowing flexible functionality without sacrificing speed or information content). To manage the complexity of the presentation of the (visual) information to the user, data instantiations may be represented in an iconified format. When the icons are picked, or selected, the data `reveal' themselves in their `native' format. Object-oriented programming and data type constructs were employed, allowing a single`look and feel' to be presented to the user for the different media types. GRAVE currently supports the following data types: imagery (from various sources of differing resolution, coverage, and projection); elevation data (from DMA and USGS); physical simulation results (atmospherics, geological, hydrologic); video acquisitions; vector data (geographical, political boundaries); and textual reports. GRAVE was developed in the Application Visualization System (AVS) Visual Programming Environment (VPE); as such it is easily modifiable and reconfigurable, supporting the integration of new processing techniques/approaches as they become available or are developed.

  5. Visual field defects in onchocerciasis.

    PubMed Central

    Thylefors, B; Tønjum, A M

    1978-01-01

    Lesions in the posterior segment of the eye in onchocerciasis may give visual field defects, but so far no detailed investigation has been done to determine the functional visual loss. Examination of the visual fields in 18 selected cases of onchocerciasis by means of a tangent screen test revealed important visual field defects associated with lesions in the posterior segment of the eye. Involvement of the optic nerve seemed to be important, giving rise to severely constricted visual fields. Cases of postneuritic optic atrophy showed a very uniform pattern of almost completely constricted visual fields, with only 5 to 10 degree central rest spared. Papillitis gave a similar severe constriction of the visual fields. The pattern of visual fields associated with optic neuropathy in onchocerciasis indicates that a progressive lesion of the optic nerve from the periphery may be responsible for the loss of vision. The visual field defects in onchocerciasis constitute a serious handicap, which must be taken into consideration when estimating the socioeconomic importance of the disease. Images PMID:678499

  6. 14 CFR 103.21 - Visual reference with the surface.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Visual reference with the surface. 103.21... (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES ULTRALIGHT VEHICLES Operating Rules § 103.21 Visual reference with the surface. No person may operate an ultralight vehicle except by visual reference with...

  7. 14 CFR 103.21 - Visual reference with the surface.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Visual reference with the surface. 103.21... (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES ULTRALIGHT VEHICLES Operating Rules § 103.21 Visual reference with the surface. No person may operate an ultralight vehicle except by visual reference with...

  8. Computer Visual System (CVS) reference manual

    SciTech Connect

    Snider, D.M.; Wagner, K.L.

    1985-01-01

    This is a reference manual for the Idaho National Engineering Laboratory (INEL) Computer Visual System (CVS). The manual contains a summary of the operation of the CVS program and describes the hardware requirements. It explains the main features and operation of the program as well as how to communicate with the host computer. CVS is a high performance color graphics system. This system enables color pictures to be generated and edited on a color raster terminal and subsequently output as 35mm color transparencies and gray-scale or black and white hard copies. CVS provides processors for the construction of word slides, tables, charts, and sketches. Commands for the creation and editing of images are entered by picking items from menus displayed on the terminal screen. The CVS program executes on a Control Data Corporation (CDC) CYBER 176 computer under the NOS operating system. The user interacts with CVS through a terminal, entering commands from a keyboard and tablet. Currently, only the Advanced Electronic Design (AED) line of color terminals are supported for graphic input to CVS. As other terminals become available, modules to drive these terminals will be included.

  9. [Visual field defects in hydrocephalus].

    PubMed

    Kojima, N; Tamaki, N; Hosoda, K; Matsumoto, S

    1985-03-01

    Eight patients representing visual field defects associated with hydrocephalus are reviewed. Seven cases had aqueductal stenosis and one had congenital communicating hydrocephalus. We found five cases of defects in visual field typical of a chiasmal or optic nerve lesion: (1) inferior altitudinal hemianopia with inferior nasal quadrantanopia in the opposite eye; (2) inferior binasal quadrantanopia; (3) unilateral inferior nasal depression; (4) unilateral temporal defect; (5) bilateral central scotoma. In these cases CT demonstrated moderate or marked symmetrical dilatation of the third and lateral ventricles. Four out of five cases showed bulging of the third ventricle anteriorly into the sella turcica on CT or ventriculography. Other three patients had incongruous homonymous hemianopia. Characteristic asymmetrical dilatation of the lateral ventricles was noted in all three cases. The more enlarged lateral ventricles were ipsilateral with the affected visual pathways. The sites of lesion responsible for these field defects seemed to be optic tract in one case and optic radiation in two cases. Ventriculoperitoneal shunt was placed in five out of seven cases. Impaired visual field improved in three patients after shunt insertion. A 28-year-old female who had history of blurred vision fos 14 days showed improvement in visual acuity and field when the enlarged ventricles became slit-like by shunting. In the other two patients defects in visual fields improved in spite of consistent ventriculomegaly. These facts suggested that not only the mechanical forces with distended third ventricle but also increased intracranial pressure played an important role in producing visual field defects in hydrocephalic patients. PMID:3874634

  10. Introduction to Vector Field Visualization

    NASA Technical Reports Server (NTRS)

    Kao, David; Shen, Han-Wei

    2010-01-01

    Vector field visualization techniques are essential to help us understand the complex dynamics of flow fields. These can be found in a wide range of applications such as study of flows around an aircraft, the blood flow in our heart chambers, ocean circulation models, and severe weather predictions. The vector fields from these various applications can be visually depicted using a number of techniques such as particle traces and advecting textures. In this tutorial, we present several fundamental algorithms in flow visualization including particle integration, particle tracking in time-dependent flows, and seeding strategies. For flows near surfaces, a wide variety of synthetic texture-based algorithms have been developed to depict near-body flow features. The most common approach is based on the Line Integral Convolution (LIC) algorithm. There also exist extensions of LIC to support more flexible texture generations for 3D flow data. This tutorial reviews these algorithms. Tensor fields are found in several real-world applications and also require the aid of visualization to help users understand their data sets. Examples where one can find tensor fields include mechanics to see how material respond to external forces, civil engineering and geomechanics of roads and bridges, and the study of neural pathway via diffusion tensor imaging. This tutorial will provide an overview of the different tensor field visualization techniques, discuss basic tensor decompositions, and go into detail on glyph based methods, deformation based methods, and streamline based methods. Practical examples will be used when presenting the methods; and applications from some case studies will be used as part of the motivation.

  11. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... meridians 221/2 degrees apart for each eye and indicate the Goldmann equivalent used. See Table III for the... visual fields. Determine the average concentric contraction of the visual field of each eye by measuring... defect are present in one or both eyes and are service connected, separately evaluate the visual...

  12. Visualizing second order tensor fields with hyperstreamlines

    NASA Technical Reports Server (NTRS)

    Delmarcelle, Thierry; Hesselink, Lambertus

    1993-01-01

    Hyperstreamlines are a generalization to second order tensor fields of the conventional streamlines used in vector field visualization. As opposed to point icons commonly used in visualizing tensor fields, hyperstreamlines form a continuous representation of the complete tensor information along a three-dimensional path. This technique is useful in visulaizing both symmetric and unsymmetric three-dimensional tensor data. Several examples of tensor field visualization in solid materials and fluid flows are provided.

  13. Complex visual hallucinations in the hemianopic field.

    PubMed Central

    Kölmel, H W

    1985-01-01

    From 120 patients with an homonymous hemianopia 16 experienced complex visual hallucinations in the hemianopic field. The brain lesion was located in the occipital lobe, though damage was not limited to this area. Complex hallucinations appeared after a latent period. They were weak in colour and stereotypical in appearance, which allowed differentiation from visual hallucinations of other causes. Different behaviour after saccadic eye movement differentiated between complex visual hallucinations in the hemianopic field and visual auras of an epileptic origin. PMID:3973619

  14. International Geomagnetic Reference Field: the third generation.

    USGS Publications Warehouse

    Peddie, N.W.

    1982-01-01

    In August 1981 the International Association of Geomagnetism and Aeronomy revised the International Geomagnetic Reference Field (IGRF). It is the second revision since the inception of the IGRF in 1968. The revision extends the earlier series of IGRF models from 1980 to 1985, introduces a new series of definitive models for 1965-1976, and defines a provisional reference field for 1975- 1980. The revision consists of: 1) a model of the main geomagnetic field at 1980.0, not continuous with the earlier series of IGRF models together with a forecast model of the secular variation of the main field during 1980-1985; 2) definitive models of the main field at 1965.0, 1970.0, and 1975.0, with linear interpolation of the model coefficients specified for intervening dates; and 3) a provisional reference field for 1975-1980, defined as the linear interpolation of the 1975 and 1980 main-field models.-from Author

  15. Mapping the Visual Communication Field.

    ERIC Educational Resources Information Center

    Moriarty, Sandra E.

    This paper discusses visual communication theory. After an examination of the literature, this study built a more extensive bibliography of visual communication in general--theory, research, teaching--as well as a taxonomy that was better grounded. A 95-page bibliography was developed for works from a number of scholarly journals dealing with…

  16. Visual Field Asymmetry in Attentional Capture

    ERIC Educational Resources Information Center

    Du, Feng; Abrams, Richard A.

    2010-01-01

    The present study examined the spatial distribution of involuntary attentional capture over the two visual hemi-fields. A new experiment, and an analysis of three previous experiments showed that distractors in the left visual field that matched a sought-for target in color produced a much larger capture effect than identical distractors in the…

  17. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... who are well adapted to intraocular lens implant or contact lens correction, visual field examinations.... For aphakic individuals not well adapted to contact lens correction or pseudophakic individuals not well adapted to intraocular lens implant, visual field examinations must be conducted using...

  18. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... who are well adapted to intraocular lens implant or contact lens correction, visual field examinations.... For aphakic individuals not well adapted to contact lens correction or pseudophakic individuals not well adapted to intraocular lens implant, visual field examinations must be conducted using...

  19. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... who are well adapted to intraocular lens implant or contact lens correction, visual field examinations.... For aphakic individuals not well adapted to contact lens correction or pseudophakic individuals not well adapted to intraocular lens implant, visual field examinations must be conducted using...

  20. 38 CFR 4.77 - Visual fields.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Visual fields. 4.77 Section 4.77 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS SCHEDULE FOR RATING DISABILITIES Disability Ratings The Organs of Special Sense § 4.77 Visual fields. (a) Examination of...

  1. EventRiver: visually exploring text collections with temporal references.

    PubMed

    Luo, Dongning; Yang, Jing; Krstajic, Milos; Ribarsky, William; Keim, Daniel A

    2012-01-01

    Many text collections with temporal references, such as news corpora and weblogs, are generated to report and discuss real life events. Thus, event-related tasks, such as detecting real life events that drive the generation of the text documents, tracking event evolutions, and investigating reports and commentaries about events of interest, are important when exploring such text collections. To incorporate and leverage human efforts in conducting such tasks, we propose a novel visual analytics approach named EventRiver. EventRiver integrates event-based automated text analysis and visualization to reveal the events motivating the text generation and the long term stories they construct. On the visualization, users can interactively conduct tasks such as event browsing, tracking, association, and investigation. A working prototype of EventRiver has been implemented for exploring news corpora. A set of case studies, experiments, and a preliminary user test have been conducted to evaluate its effectiveness and efficiency. PMID:22076487

  2. The International Geomagnetic Reference Field, 2005

    USGS Publications Warehouse

    Rukstales, Kenneth S.; Love, Jeffrey J.

    2007-01-01

    This is a set of five world charts showing the declination, inclination, horizontal intensity, vertical component, and total intensity of the Earth's magnetic field at mean sea level at the beginning of 2005. The charts are based on the International Geomagnetic Reference Field (IGRF) main model for 2005 and secular change model for 2005-2010. The IGRF is referenced to the World Geodetic System 1984 ellipsoid. Additional information about the USGS geomagnetism program is available at: http://geomag.usgs.gov/

  3. Uniformity of accommodation across the visual field.

    PubMed

    Liu, Tao; Sreenivasan, Vidhyapriya; Thibos, Larry N

    2016-01-01

    We asked the question: Does accommodation change the eye's focusing power equally over the central visual field in emmetropic and myopic adult eyes? To answer this question we modified our laboratory scanning wavefront aberrometer to rapidly measure ocular refractive state over the central 30° diameter of visual field as a function of foveal accommodative demand. On average, ocular refractive state changed uniformly over the central visual field as the eye accommodated up to 6 D. Visual field maps of accommodative error (relative to a spherical target surface of constant vergence) reveal subtle patterns of deviation on the order of ± 0.5 D that are unique to the individual and relatively invariant to changes in accommodative state. Population mean maps for accommodative error are remarkably uniform across the central visual field, indicating the retina of the hypothetical "average eye" is conjugate to a sphere of constant target vergence for all states of accommodation, even though individual eyes might deviate from the mean due to random variations. No systematic difference between emmetropic and myopic eyes was evident. Since accuracy of accommodation across the central visual field is similar to that measured in the fovea, loss of image quality due to accommodative errors, which potentially drives myopia and may affect many aspects of visual function, will be similar across the central retina. PMID:26842859

  4. Hemispace-visual field interactions in visual extinction.

    PubMed

    Rapcsak, S Z; Watson, R T; Heilman, K M

    1987-09-01

    Visual extinction was studied in a patient with neglect from a right hemispheric lesion. Extinction occurred during double simultaneous stimulation within the same visual hemi-field (VHF). This finding suggests that interhemispheric rivalry is not a critical factor. During double simultaneous stimulation within the same VHF as well as with stimuli in different VHFs, the severity of extinction was determined by both the retinotopic and the hemi-spatial position of the extinguished stimulus. The location of the other stimulus, however, did not seem relevant. It is proposed that damage to a corticolimbic-reticular system reduces attentional capacity and that extinction during double simultaneous stimulation in the visual modality reflects an inability to distribute the limited attentional resources equally to two different locations. The severity of extinction is a measure of an unequal distribution of attention along a gradient within visual space. PMID:3668561

  5. Visual field restorative rehabilitation after brain injury.

    PubMed

    Matteo, Barbara Maria; Viganò, Barbara; Cerri, Cesare Giuseppe; Perin, Cecilia

    2016-07-01

    About 20%-30% of patients undergoing neurological rehabilitation report visual field defects, one of the most frequent of which is homonymous hemianopsia (loss of the same half of the visual field in both eyes). There is still no consensus as to whether homonymous hemianopsia is best treated in a restorative or compensatory manner. The aim of this review is to describe the effects of restorative rehabilitation, whose long-term efficacy is still being debated. We analyzed 56 articles describing the use of various techniques used to promote visual field recovery but concentrating on two approaches: "border training," which involves exercising vision at the edge of the damaged visual field, and "blindsight training," which is based on exercising unconscious perceptual functions in the mild of the blind hemifield where the scotoma is deep. Both techniques have been supported by functional imaging studies showing evidence of cortical rearrangement (plasticity) after rehabilitation. Although no formal meta-analysis was possible, the results of a semiquantitative evaluation suggested that the improvement in visual skills obtained is related to the type of training used: Border rehabilitation seems to improve the detection of visual stimuli, whereas blindsight rehabilitation seems to improve their processing. Finally, the addition of transcranial direct current stimulation seems to enhance the effects of visual field rehabilitation. PMID:27472498

  6. Visualizing vector field topology in fluid flows

    NASA Technical Reports Server (NTRS)

    Helman, James L.; Hesselink, Lambertus

    1991-01-01

    Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.

  7. Simulating binocular vision for no-reference 3D visual quality measurement.

    PubMed

    Zhou, Wu-Jie; Yu, Lu; Wu, Ming-Wei

    2015-09-01

    Perceptual quality measurement of three-dimensional (3D) visual signals has become a fundamental challenge in 3D imaging fields. This paper proposes a novel no-reference (NR) 3D visual quality measurement (VQM) metric that uses simulations of the primary visual cortex (V1) of binocular vision. As the major technical contribution of this study, perceptual properties of simple and complex cells are considered for NR 3D-VQM. More specifically, the metric simulates the receptive fields of simple cells (one class of V1 neurons) using Gaussian derivative functions, and the receptive fields of complex cells (the other class of V1 neurons) using disparity energy responses and binocular rivalry responses. Subsequently, various quality-aware features are extracted from the primary visual cortex; these will change in the presence of distortions. Finally, those features are mapped to the subjective quality score of the distorted 3D visual signal by using support vector regression (SVR). Experiments on two publicly available 3D databases confirm the effectiveness of our proposed metric, compared to the relevant full-reference (FR) and NR metrics. PMID:26368467

  8. Automated objective characterization of visual field defects in 3D

    NASA Technical Reports Server (NTRS)

    Fink, Wolfgang (Inventor)

    2006-01-01

    A method and apparatus for electronically performing a visual field test for a patient. A visual field test pattern is displayed to the patient on an electronic display device and the patient's responses to the visual field test pattern are recorded. A visual field representation is generated from the patient's responses. The visual field representation is then used as an input into a variety of automated diagnostic processes. In one process, the visual field representation is used to generate a statistical description of the rapidity of change of a patient's visual field at the boundary of a visual field defect. In another process, the area of a visual field defect is calculated using the visual field representation. In another process, the visual field representation is used to generate a statistical description of the volume of a patient's visual field defect.

  9. Icy Schwedeneck field may provide reference

    SciTech Connect

    Not Available

    1985-05-01

    Situated in an icy region of the Baltic Sea, Germany's first offshore field may provide the nation with the reference needed to encroach the arctic market. Production began last winter from one platform in the Schwedeneck-See field, located about three miles off the Baltic Coast. Total reserves have been estimated at more than 18 million bbl. Yearly production by the end of 1986 has been estimated at 294,000 bbl. The first two production platforms were installed in late 1983 in water depths ranging from 50 to 80 ft. Because of the ice hazards inherent in the Baltic, the platforms are concrete designed with steel decks.

  10. No-reference visual quality assessment for image inpainting

    NASA Astrophysics Data System (ADS)

    Voronin, V. V.; Frantc, V. A.; Marchuk, V. I.; Sherstobitov, A. I.; Egiazarian, K.

    2015-03-01

    Inpainting has received a lot of attention in recent years and quality assessment is an important task to evaluate different image reconstruction approaches. In many cases inpainting methods introduce a blur in sharp transitions in image and image contours in the recovery of large areas with missing pixels and often fail to recover curvy boundary edges. Quantitative metrics of inpainting results currently do not exist and researchers use human comparisons to evaluate their methodologies and techniques. Most objective quality assessment methods rely on a reference image, which is often not available in inpainting applications. Usually researchers use subjective quality assessment by human observers. It is difficult and time consuming procedure. This paper focuses on a machine learning approach for no-reference visual quality assessment for image inpainting based on the human visual property. Our method is based on observation that Local Binary Patterns well describe local structural information of the image. We use a support vector regression learned on assessed by human images to predict perceived quality of inpainted images. We demonstrate how our predicted quality value correlates with qualitative opinion in a human observer study. Results are shown on a human-scored dataset for different inpainting methods.

  11. No-reference quality assessment based on visual perception

    NASA Astrophysics Data System (ADS)

    Li, Junshan; Yang, Yawei; Hu, Shuangyan; Zhang, Jiao

    2014-11-01

    The visual quality assessment of images/videos is an ongoing hot research topic, which has become more and more important for numerous image and video processing applications with the rapid development of digital imaging and communication technologies. The goal of image quality assessment (IQA) algorithms is to automatically assess the quality of images/videos in agreement with human quality judgments. Up to now, two kinds of models have been used for IQA, namely full-reference (FR) and no-reference (NR) models. For FR models, IQA algorithms interpret image quality as fidelity or similarity with a perfect image in some perceptual space. However, the reference image is not available in many practical applications, and a NR IQA approach is desired. Considering natural vision as optimized by the millions of years of evolutionary pressure, many methods attempt to achieve consistency in quality prediction by modeling salient physiological and psychological features of the human visual system (HVS). To reach this goal, researchers try to simulate HVS with image sparsity coding and supervised machine learning, which are two main features of HVS. A typical HVS captures the scenes by sparsity coding, and uses experienced knowledge to apperceive objects. In this paper, we propose a novel IQA approach based on visual perception. Firstly, a standard model of HVS is studied and analyzed, and the sparse representation of image is accomplished with the model; and then, the mapping correlation between sparse codes and subjective quality scores is trained with the regression technique of least squaresupport vector machine (LS-SVM), which gains the regressor that can predict the image quality; the visual metric of image is predicted with the trained regressor at last. We validate the performance of proposed approach on Laboratory for Image and Video Engineering (LIVE) database, the specific contents of the type of distortions present in the database are: 227 images of JPEG2000, 233

  12. Monoenergetic fast neutron reference fields: II. Field characterization

    NASA Astrophysics Data System (ADS)

    Nolte, Ralf; Thomas, David J.

    2011-12-01

    Monoenergetic neutron reference fields are required for the calibration of neutron detectors and dosemeters for various applications ranging from nuclear physics and nuclear data measurements to radiation protection. In a series of two separate publications the metrological aspects of the production and measurement of fast neutrons are reviewed. In the first part, requirements for the nuclear reactions used to produce neutron fields as well as methods for target characterization and the general layout of reference facilities were discussed. This second part focuses on the most important techniques for field characterization and includes the determination of the neutron fluence as well as the spectral neutron distribution and the determination of the fluence of contaminating photons. The measurements are usually carried out relative to reference cross sections which are reviewed in a separate contribution, but for certain conditions 'absolute' methods for neutron measurements can be used which are directly traceable to the international system of units (SI).

  13. Visual field testing with red targets.

    PubMed

    Mindel, J S; Safir, A; Schare, P W

    1983-06-01

    Ten patients with partial temporal visual field defects were examined with a modified tangent screen projection perimeter (Auto-Plot). Defects demonstrated with an isopter for chromatic recognition of a 3-mm red stimulus could always be reproduced with an isopter for achromatic recognition of a dim, 3-mm white stimulus. The red-white intensity ratio producing equivalent fields remained constant for a given patient but varied from subject to subject (range, 3.0 to 7.5; mean, 5.7; SD, 1.8). Thus, red functioned as dim white, but no single fixed ratio of intensities was applicable to all subjects. Visual field testing with 1 foot-candle of tangent screen illumination permitted subjects to adapt to dark. As retinal sensitivities increased, the corresponding visual field steadily enlarged for 30 minutes. This effect was greater in the pathologic temporal fields, which increased relatively more than intact nasal fields. The result was poor visual field reproducibility with time. PMID:6860207

  14. Visualization of 3-D tensor fields

    NASA Technical Reports Server (NTRS)

    Hesselink, L.

    1996-01-01

    Second-order tensor fields have applications in many different areas of physics, such as general relativity and fluid mechanics. The wealth of multivariate information in tensor fields makes them more complex and abstract than scalar and vector fields. Visualization is a good technique for scientists to gain new insights from them. Visualizing a 3-D continuous tensor field is equivalent to simultaneously visualizing its three eigenvector fields. In the past, research has been conducted in the area of two-dimensional tensor fields. It was shown that degenerate points, defined as points where eigenvalues are equal to each other, are the basic singularities underlying the topology of tensor fields. Moreover, it was shown that eigenvectors never cross each other except at degenerate points. Since we live in a three-dimensional world, it is important for us to understand the underlying physics of this world. In this report, we describe a new method for locating degenerate points along with the conditions for classifying them in three-dimensional space. Finally, we discuss some topological features of three-dimensional tensor fields, and interpret topological patterns in terms of physical properties.

  15. A computational theory of visual receptive fields.

    PubMed

    Lindeberg, Tony

    2013-12-01

    A receptive field constitutes a region in the visual field where a visual cell or a visual operator responds to visual stimuli. This paper presents a theory for what types of receptive field profiles can be regarded as natural for an idealized vision system, given a set of structural requirements on the first stages of visual processing that reflect symmetry properties of the surrounding world. These symmetry properties include (i) covariance properties under scale changes, affine image deformations, and Galilean transformations of space-time as occur for real-world image data as well as specific requirements of (ii) temporal causality implying that the future cannot be accessed and (iii) a time-recursive updating mechanism of a limited temporal buffer of the past as is necessary for a genuine real-time system. Fundamental structural requirements are also imposed to ensure (iv) mutual consistency and a proper handling of internal representations at different spatial and temporal scales. It is shown how a set of families of idealized receptive field profiles can be derived by necessity regarding spatial, spatio-chromatic, and spatio-temporal receptive fields in terms of Gaussian kernels, Gaussian derivatives, or closely related operators. Such image filters have been successfully used as a basis for expressing a large number of visual operations in computer vision, regarding feature detection, feature classification, motion estimation, object recognition, spatio-temporal recognition, and shape estimation. Hence, the associated so-called scale-space theory constitutes a both theoretically well-founded and general framework for expressing visual operations. There are very close similarities between receptive field profiles predicted from this scale-space theory and receptive field profiles found by cell recordings in biological vision. Among the family of receptive field profiles derived by necessity from the assumptions, idealized models with very good qualitative

  16. Visualization of tensor fields using superquadric glyphs.

    PubMed

    Ennis, Daniel B; Kindlman, Gordon; Rodriguez, Ignacio; Helm, Patrick A; McVeigh, Elliot R

    2005-01-01

    The spatially varying tensor fields that arise in magnetic resonance imaging are difficult to visualize due to the multivariate nature of the data. To improve the understanding of myocardial structure and function a family of objects called glyphs, derived from superquadric parametric functions, are used to create informative and intuitive visualizations of the tensor fields. The superquadric glyphs are used to visualize both diffusion and strain tensors obtained in canine myocardium. The eigensystem of each tensor defines the glyph shape and orientation. Superquadric functions provide a continuum of shapes across four distinct eigensystems (lambda(i), sorted eigenvalues), lambda(1) = lambda(2) = lambda(3) (spherical), lambda(1) < lambda(2) = lambda(3) (oblate), lambda(1) > lambda(2) = lambda(3) (prolate), and lambda(1) > lambda(2) > lambda(3) (cuboid). The superquadric glyphs are especially useful for identifying regions of anisotropic structure and function. Diffusion tensor renderings exhibit fiber angle trends and orthotropy (three distinct eigenvalues). Visualization of strain tensors with superquadric glyphs compactly exhibits radial thickening gradients, circumferential and longitudinal shortening, and torsion combined. The orthotropic nature of many biologic tissues and their DTMRI and strain data require visualization strategies that clearly exhibit the anisotropy of the data if it is to be interpreted properly. Superquadric glyphs improve the ability to distinguish fiber orientation and tissue orthotropy compared to ellipsoids. PMID:15690516

  17. Spatial invariance of visual receptive fields in parietal cortex neurons.

    PubMed

    Duhamel, J R; Bremmer, F; Ben Hamed, S; Graf, W

    1997-10-23

    Spatial information is conveyed to the primary visual cortex in retinal coordinates. Movement trajectory programming, however, requires a transformation from this sensory frame of reference into a frame appropriate for the selected part of the body, such as the eye, head or arms. To achieve this transformation, visual information must be combined with information from other sources: for instance, the location of an object of interest can be defined with respect to the observer's head if the position of the eyes in the orbit is known and is added to the object's retinal coordinates. Here we show that in a subdivision of the monkey parietal lobe, the ventral intraparietal area (VIP), the activity of visual neurons is modulated by eye-position signals, as in many other areas of the cortical visual system. We find that individual receptive fields of a population of VIP neurons are organized along a continuum, from eye to head coordinates. In the latter case, neurons encode the azimuth and/or elevation of a visual stimulus, independently of the direction in which the eyes are looking, thus representing spatial locations explicitly in at least a head-centred frame of reference. PMID:9349815

  18. Visualizing underwater acoustic matched-field processing

    NASA Astrophysics Data System (ADS)

    Rosenblum, Lawrence; Kamgar-Parsi, Behzad; Karahalios, Margarida; Heitmeyer, Richard

    1991-06-01

    Matched-field processing is a new technique for processing ocean acoustic data measured by an array of hydrophones. It produces estimates of the location of sources of acoustic energy. This method differs from source localization techniques in other disciplines in that it uses the complex underwater acoustic environment to improve the accuracy of the source localization. An unexplored problem in matched-field processing has been to separate multiple sources within a matched-field ambiguity function. Underwater acoustic processing is one of many disciplines where a synthesis of computer graphics and image processing is producing new insight. The benefits of different volume visualization algorithms for matched-field display are discussed. The authors show how this led to a template matching scheme for identifying a source within the matched-field ambiguity function that can help move toward an automated source localization process.

  19. Visualization of a changing dose field.

    SciTech Connect

    Helm, T. M; Kornreich, D. E.

    2002-01-01

    To help visualize the results of dose modeling for nuclear materials processing opcrations, we have developed an integrated model that uses a simple dosc calculation tool to obtain estimates of the dose field in a complex geomctry and then post-process the data to produce a video of the now time-dependent data. We generate two-dimensional radiation fields within an existing physical cnvironment and then analyze them using three-dimensional visualization techniques. The radiation fields are generated for both neutrons and photons. Standard monoenergetic diffusion theory is used to estimate the neutron dosc fields. The photon dose is estimated using a point-kernel formalism, with photon shielding effects and buildup taken into account. The radiation field dynamics are analyzed by interleaving individual 3D graphic 'snapshots' into a smoothed, lime dependent, video-based display. In-the-room workers are 'seen' in the radiation fields via a graphical, 3D fly-through rendering of the room. Worker dose levels can reveal surprising dependencies on operational source placement, source types, worker alignment, shielding alignments, and indirect operations from external workers.

  20. Visual cortex in aging and Alzheimer's disease: changes in visual field maps and population receptive fields

    PubMed Central

    Brewer, Alyssa A.; Barton, Brian

    2012-01-01

    Although several studies have suggested that cortical alterations underlie such age-related visual deficits as decreased acuity, little is known about what changes actually occur in visual cortex during healthy aging. Two recent studies showed changes in primary visual cortex (V1) during normal aging; however, no studies have characterized the effects of aging on visual cortex beyond V1, important measurements both for understanding the aging process and for comparison to changes in age-related diseases. Similarly, there is almost no information about changes in visual cortex in Alzheimer's disease (AD), the most common form of dementia. Because visual deficits are often reported as one of the first symptoms of AD, measurements of such changes in the visual cortex of AD patients might improve our understanding of how the visual system is affected by neurodegeneration as well as aid early detection, accurate diagnosis and timely treatment of AD. Here we use fMRI to first compare the visual field map (VFM) organization and population receptive fields (pRFs) between young adults and healthy aging subjects for occipital VFMs V1, V2, V3, and hV4. Healthy aging subjects do not show major VFM organizational deficits, but do have reduced surface area and increased pRF sizes in the foveal representations of V1, V2, and hV4 relative to healthy young control subjects. These measurements are consistent with behavioral deficits seen in healthy aging. We then demonstrate the feasibility and first characterization of these measurements in two patients with mild AD, which reveal potential changes in visual cortex as part of the pathophysiology of AD. Our data aid in our understanding of the changes in the visual processing pathways in normal aging and provide the foundation for future research into earlier and more definitive detection of AD. PMID:24570669

  1. Improved visualization of flow field measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1991-01-01

    A capability is proposed that makes it feasible to apply to measured flow field data the visualization tools developed to display numerical solutions for computational fluid dynamic problems. The measurement monitor surface (MMS) methodology was used for the analysis of flow field measurements within a low-aspect-ratio transonic axial-flow fan rotor acquired with two-dimensional laser anemometry. It is shown that the MMS method may be utilized to generate input for the multidimensional processing and analytical tools developed for numerical flow field simulation data. Thus an experimenter utilizing an interactive graphics program could illustrate scalar quantities such as Mach number by profiles, contour lines, carpet plots, and surfaces employing various color intensities. Also, flow directionality can be shown by the display of vector fields and particle traces.

  2. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  3. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  4. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  5. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  6. 21 CFR 886.1360 - Visual field laser instrument.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Visual field laser instrument. 886.1360 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1360 Visual field laser instrument. (a) Identification. A visual field laser instrument is an AC-powered device intended to...

  7. Flow field visualization about external axial corners

    NASA Technical Reports Server (NTRS)

    Talcott, N. A., Jr.

    1978-01-01

    An experimental investigation was conducted to visualize the flow field about external axial corners. The investigation was initiated to provide answers to questions about the inviscid flow pattern for continuing numerical investigations. Symmetrical and asymmetrical corner models were tested at a Reynolds number per meter of 60,700,000. Oil-flow and vapor-screen photographs were taken for both models at angle of attack and yaw. The paper presents the results of the investigation in the form of oil-flow photographs and the surrounding shock wave location obtained from the vapor screens.

  8. Visualization of circuit card electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Zwillinger, Daniel

    1995-01-01

    Circuit boards are used in nearly every electrical appliance. Most board failures cause differing currents in the circuit board traces and components. This causes the circuit board to radiate a differing electromagnetic field. Imaging this radiated field, which is equivalent to measuring the field, could be used for error detection. Using estimates of the fields radiated by a low power digital circuit board, properties of known materials, and available equipment, we determined how well the following technologies could be used to visualize circuit board electromagnetic fields (prioritized by promise): electrooptical techniques, magnetooptical techniques, piezoelectric techniques, thermal techniques, and electrodynamic force technique. We have determined that sensors using the electrooptical effect (Pockels effect) appear to be sufficiently sensitive for use in a circuit board imaging system. Sensors utilizing the magnetooptical effect may also be adequate for this purpose, when using research materials. These sensors appear to be capable of achieving direct broadband measurements. We also reviewed existing electromagnetic field sensors. Only one of the sensors (recently patented) was specifically designed for circuit board measurements.

  9. Visual field constriction as a cause of blindness or visual impairment.

    PubMed Central

    Murdoch, I. E.; Jones, B. R.; Cousens, S.; Liman, I.; Babalola, O. E.; Dauda, J.; Abiose, A.

    1997-01-01

    Reported are the results of a study of onchocerciasis in communities mesoendemic for savanna onchocerciasis in Kaduna State, northern Nigeria. The study involved 6831 individuals aged > or = 5 years who underwent an extensive screening examination for visual function including Friedmann field analysis. A total of 185 (2.7%) were bilaterally blind by acuity and an additional 28 (0.4%) were blind by visual field constriction. Also 118 (1.7%) individuals were visually impaired by acuity criteria. No criteria for visual impairment by field constriction have been established, and we therefore investigated three potential criteria. As a result, a further 60 (0.9%) individuals were identified with significant visual impairment due to field loss by the various definitions. Small islands of remaining peripheral field occurred in 50 individuals, while 40 individuals had marked reduction of binocular visual field below the horizontal meridian. Concentric visual field constriction to < 20 degrees was found in seven individuals. The WHO definition of blindness currently includes visual field damage criteria for blindness but not for visual impairment. Visual field loss is recognized as a major disability. We hope that these findings stimulate international discussion leading to the development of satisfactory definitions for visual impairment by visual field constriction. PMID:9185366

  10. Individual differences in visual field shape modulate the effects of attention on the lower visual field advantage in crowding

    PubMed Central

    Fortenbaugh, Francesca C.; Silver, Michael A.; Robertson, Lynn C.

    2015-01-01

    It has previously been reported that visual crowding of a target by flankers is stronger in the upper visual field than in the lower, and this finding has been attributed to greater attentional resolution in the lower hemifield (He, Cavanagh, & Intriligator, 1996). Here we show that the upper/lower asymmetry in visual crowding can be explained by natural variations in the borders of each individual's visual field. Specifically, asymmetry in crowding along the vertical meridian can be almost entirely accounted for by replacing the conventional definition of visual field location, in units of degrees of visual angle, with a definition based on the ratio of the extents of an individual's upper and lower visual field. We also show that the upper/lower crowding asymmetry is eliminated when stimulus eccentricity is expressed in units of percentage of visual field extent but is present when the conventional measure of visual angle is used. We further demonstrate that the relationship between visual field extent and perceptual asymmetry is most evident when participants are able to focus their attention on the target location. These results reveal important influences of visual field boundaries on visual perception, even for visual field locations far from those boundaries. PMID:25761337

  11. Anosognosia for obvious visual field defects in stroke patients.

    PubMed

    Baier, Bernhard; Geber, Christian; Müller-Forell, Wiebke; Müller, Notger; Dieterich, Marianne; Karnath, Hans-Otto

    2015-01-01

    Patients with anosognosia for visual field defect (AVFD) fail to recognize consciously their visual field defect. There is still unclarity whether specific neural correlates are associated with AVFD. We studied AVFD in 54 patients with acute stroke and a visual field defect. Nineteen percent of this unselected sample showed AVFD. By using modern voxelwise lesion-behaviour mapping techniques we found an association between AVFD and parts of the lingual gyrus, the cuneus as well as the posterior cingulate and corpus callosum. Damage to these regions appears to induce unawareness of visual field defects and thus may play a significant role for conscious visual perception. PMID:24652382

  12. The study on computer aided peripheral visual field diagnosis.

    PubMed

    Shuyi, Wang; Xingsan, Qian

    2005-01-01

    Background Despite the widespread adoption of automated perimetry, there is still a role for peripheral perimetry. So far there was no accurate quantitative analysis on the change of visual field, most analysis were qualitative and depend on doctor's experience. Method Computer aided diagnose system was designed to judge the accurate change in visual field. Tabu Seach technology was used to identify visual field from the result of Peripheral perimeter test, and accurate visual filed defect dimension can be concluded by compared with point to point. At the same time liable eye diseases were predicted by computer. Conclusion Computer aided peripheral visual field diagnose system can identify defect in visual field, and provide reliable clinical diagnosis. Key words peripheral visual field, Computer aided diagnose, tabu search. PMID:17282924

  13. Mechanisms Underlying Development of Visual Maps and Receptive Fields

    PubMed Central

    Huberman, Andrew D.; Feller, Marla B.; Chapman, Barbara

    2008-01-01

    Patterns of synaptic connections in the visual system are remarkably precise. These connections dictate the receptive field properties of individual visual neurons and ultimately determine the quality of visual perception. Spontaneous neural activity is necessary for the development of various receptive field properties and visual feature maps. In recent years, attention has shifted to understanding the mechanisms by which spontaneous activity in the developing retina, lateral geniculate nucleus, and visual cortex instruct the axonal and dendritic refinements that give rise to orderly connections in the visual system. Axon guidance cues and a growing list of other molecules, including immune system factors, have also recently been implicated in visual circuit wiring. A major goal now is to determine how these molecules cooperate with spontaneous and visually evoked activity to give rise to the circuits underlying precise receptive field tuning and orderly visual maps. PMID:18558864

  14. GlyphSea: Visualizing Vector Fields

    NASA Astrophysics Data System (ADS)

    McQuinn, Emmett; Chourasia, Amit; Schulze, Jürgen P.; Minster, Jean-Bernard

    2013-12-01

    Understanding vector fields is important in many science and engineering domains. Often glyphs are used to represent vector data as arrows, cones, ellipsoids, and other geometric shapes. When implemented using traditional 3D graphics, these glyphs have drawbacks of being view dependent, orientation ambiguous, and requiring specific geometric resolution. We propose a straightforward new method of procedural dipole texturing of glyph shapes, which overcomes these drawbacks and can enhance existing methods. We demonstrate our method with an interactive application (GlyphSea), which incorporates additional features such as screen space ambient occlusion, glyph displacement, lattices, halos and other contextual visual cues. We also discuss the results and informal feedback from scientists on insights gained by exploring time varying vector datasets in astrophysics and seismology.

  15. A reference guide for tree analysis and visualization

    PubMed Central

    2010-01-01

    The quantities of data obtained by the new high-throughput technologies, such as microarrays or ChIP-Chip arrays, and the large-scale OMICS-approaches, such as genomics, proteomics and transcriptomics, are becoming vast. Sequencing technologies become cheaper and easier to use and, thus, large-scale evolutionary studies towards the origins of life for all species and their evolution becomes more and more challenging. Databases holding information about how data are related and how they are hierarchically organized expand rapidly. Clustering analysis is becoming more and more difficult to be applied on very large amounts of data since the results of these algorithms cannot be efficiently visualized. Most of the available visualization tools that are able to represent such hierarchies, project data in 2D and are lacking often the necessary user friendliness and interactivity. For example, the current phylogenetic tree visualization tools are not able to display easy to understand large scale trees with more than a few thousand nodes. In this study, we review tools that are currently available for the visualization of biological trees and analysis, mainly developed during the last decade. We describe the uniform and standard computer readable formats to represent tree hierarchies and we comment on the functionality and the limitations of these tools. We also discuss on how these tools can be developed further and should become integrated with various data sources. Here we focus on freely available software that offers to the users various tree-representation methodologies for biological data analysis. PMID:20175922

  16. Vector Field Visual Data Analysis Technologies for Petascale Computational Science

    SciTech Connect

    Garth, Christoph; Deines, Eduard; Joy, Kenneth I.; Bethel, E. Wes; Childs, Hank; Weber, Gunther; Ahern, Sean; Pugmire, Dave; Sanderson, Allen; Johnson, Chris

    2009-11-13

    State-of-the-art computational science simulations generate large-scale vector field data sets. Visualization and analysis is a key aspect of obtaining insight into these data sets and represents an important challenge. This article discusses possibilities and challenges of modern vector field visualization and focuses on methods and techniques developed in the SciDAC Visualization and Analytics Center for Enabling Technologies (VACET) and deployed in the open-source visualization tool, VisIt.

  17. The Egocentric Reference for Visual Exploration and Orientation

    ERIC Educational Resources Information Center

    Nico, Daniele; Daprati, Elena

    2009-01-01

    Clinical signs of damage to the egocentric reference system range from the inability to detect stimuli in the real environment to a defect in recovering items from an internal representation. Despite clinical dissociations, current interpretations consider all symptoms as due to a single perturbation, differentially expressed according to the…

  18. Blindness and Visual Impairments: National Information and Advocacy Organizations. Reference Circular No. 90-2.

    ERIC Educational Resources Information Center

    Library of Congress, Washington, DC. National Library Service for the Blind and Physically Handicapped.

    This reference circular lists organizations that provide a variety of direct services to blind and visually impaired persons, including advocacy and employment programs, assistive devices, and publications offered in special format. Many of the organizations also offer guidance to families of blind and visually impaired persons and training for…

  19. Visualization of second order tensor fields and matrix data

    NASA Technical Reports Server (NTRS)

    Delmarcelle, Thierry; Hesselink, Lambertus

    1992-01-01

    We present a study of the visualization of 3-D second order tensor fields and matrix data. The general problem of visualizing unsymmetric real or complex Hermitian second order tensor fields can be reduced to the simultaneous visualization of a real and symmetric second order tensor field and a real vector field. As opposed to the discrete iconic techniques commonly used in multivariate data visualization, the emphasis is on exploiting the mathematical properties of tensor fields in order to facilitate their visualization and to produce a continuous representation of the data. We focus on interactively sensing and exploring real and symmetric second order tensor data by generalizing the vector notion of streamline to the tensor concept of hyperstreamline. We stress the importance of a structural analysis of the data field analogous to the techniques of vector field topology extraction in order to obtain a unique and objective representation of second order tensor fields.

  20. Methods of approximation of reference fields of different classes

    NASA Astrophysics Data System (ADS)

    Kolesova, Valentina I.

    1993-11-01

    The summary geomagnetic field on the reference field for the regional anomalies is surface of the Earth consists of the follow- the sum of the main geomagnetic field and ing components: the intermediate anomalies. Since the components mentioned above have the F0 = Fm + Fim + Fr + F1 + F (1) different space-spectral characteristics, different methods are used for the analytiwhere cal descriptions. The main geomagnetic field, being the global reference field, is approximated by F0 - the observed geomagnetic field the optimal way as a spherical harmonic Fm - the main geomagnetic field series [1]: Fim - the field of the intermediate anoma- n lies Fr - the field of the regional anomalies X = (g cosm\\ + n=i m=O F1 - the field of the local anomalies, - the external geomagnetic field.

  1. Enhanced visual fields in hammerhead sharks.

    PubMed

    McComb, D M; Tricas, T C; Kajiura, S M

    2009-12-01

    Several factors that influence the evolution of the unusual head morphology of hammerhead sharks (family Sphyrnidae) are proposed but few are empirically tested. In this study we tested the 'enhanced binocular field' hypothesis (that proposes enhanced frontal binocularity) by comparison of the visual fields of three hammerhead species: the bonnethead shark, Sphyrna tiburo, the scalloped hammerhead shark, Sphyrna lewini, and the winghead shark, Eusphyra blochii, with that of two carcharhinid species: the lemon shark, Negaprion brevirostris, and the blacknose shark, Carcharhinus acronotus. Additionally, eye rotation and head yaw were quantified to determine if species compensate for large blind areas anterior to the head. The winghead shark possessed the largest anterior binocular overlap (48 deg.) and was nearly four times larger than that of the lemon (10 deg.) and blacknose (11 deg.) sharks. The binocular overlap in the scalloped hammerhead sharks (34 deg.) was greater than the bonnethead sharks (13 deg.) and carcharhinid species; however, the bonnethead shark did not differ from the carcharhinids. These results indicate that binocular overlap has increased with lateral head expansion in hammerhead sharks. The hammerhead species did not demonstrate greater eye rotation in the anterior or posterior direction. However, both the scalloped hammerhead and bonnethead sharks exhibited greater head yaw during swimming (16.9 deg. and 15.6 deg., respectively) than the lemon (15.1 deg.) and blacknose (15.0 deg.) sharks, indicating a behavioral compensation for the anterior blind area. This study illustrates the larger binocular overlap in hammerhead species relative to their carcharhinid sister taxa and is consistent with the 'enhanced binocular field' hypothesis. PMID:19946079

  2. Red square test for visual field screening. A sensitive and simple bedside test.

    PubMed

    Mandahl, A

    1994-12-01

    A reliable bedside test for screening of visual field defects is a valuable tool in the examination of patients with a putative disease affecting the sensory visual pathways. Conventional methods such as Donders' confrontation method, counting fingers in the visual field periphery, of two-hand confrontation are not sufficiently sensitive to detect minor but nevertheless serious visual field defects. More sensitive methods requiring only simple tools are also described. In this study, a test card with four red squares surrounding a fixation target, a black dot, with a total test area of about 11 x 12.5 degrees at a distance of 30 cm, was designed for testing experience of red colour saturation in four quadrants, red square test. The Goldmann visual field was used as reference. 125 consecutive patients with pituitary adenoma (159 eyes), craniopharyngeoma (9 eyes), meningeoma (21 eyes), vascular hemisphere lesion (40 eyes), hemisphere tumour (10 eyes) and hemisphere abscess (2 eyes) were examined. The Goldmann visual field and red square test were pathological in pituitary adenomas in 35%, in craniopharyngeomas in 44%, in meningeomas in 52% and in hemisphere tumours or abscess in 100% of the eyes. Among these, no false-normal or false-pathological tests were found. However, in vascular hemisphere disease the corresponding figures were Goldmann visual field 90% and red square test 85%. The 5% difference (4 eyes) was due to Goldmann visual field defects strictly peripheral to the central 15 degrees. These defects were easily diagnosed with two-hand confrontation and PMID:7747575

  3. Visual field loss while wearing full-face respiratory protection.

    PubMed

    Zelnick, S D; McKay, R T; Lockey, J E

    1994-04-01

    The loss of visual field was quantified for 21 test subjects while they wore three full-face respirators. Changes in visual field were quantified for each type of respirator using a modified Goldmann projection perimeter. The loss of visual field was determined by calculating the area under the curve while wearing a respirator to that while wearing no respirator. Distinct patterns of visual field loss were apparent for the different style respirators. Analysis of the patterns could lead to the design of full-face respirators with improved visual qualities, which could improve worker safety for certain occupations. This technique also could be of help when selecting models of respiratory protection when certain visual fields must be maintained. PMID:8209836

  4. The Dynamics of Reference and Shared Visual Attention

    PubMed Central

    Dale, Rick; Kirkham, Natasha Z.; Richardson, Daniel C.

    2011-01-01

    In the tangram task, two participants are presented with the same set of abstract shapes portrayed in different orders. One participant must instruct the other to arrange their shapes so that the orders match. To do this, they must find a way to refer to the abstract shapes. In the current experiment, the eye movements of pairs of participants were tracked while they were engaged in a computerized version of the task. Results revealed the canonical tangram effect: participants became faster at completing the task from round 1 to round 3. Also, their eye-movements synchronized over time. Cross-recurrence analysis was used to quantify this coordination, and showed that as participants’ words coalesced, their actions approximated a single coordinated system. PMID:22164151

  5. A proposed International Geomagnetic Reference Field for 1965- 1985.

    USGS Publications Warehouse

    Peddie, N.W.; Fabiano, E.B.

    1982-01-01

    A set of spherical harmonic models describing the Earth's main magnetic field from 1965 to 1985 has been developed and is proposed as the next revision of the International Geomagnetic Reference Field (IGRF). A tenth degree and order spherical harmonic model of the main field was derived from Magsat data. A series of eighth degree and order spherical harmonic models of the secular variation of the main field was derived from magnetic observatory annual mean values. Models of the main field at 1965, 1970, 1975, and 1980 were obtained by extrapolating the main-field model using the secular variation models.-Authors spherical harmonic models Earth main magnetic field Magsat data

  6. Visual asymmetry revisited: Mind wandering preferentially disrupts processing in the left visual field.

    PubMed

    Kam, Julia W Y; Nagamatsu, Lindsay S; Handy, Todd C

    2014-10-29

    An emerging theory proposes that visual attention operates in parallel at two distinct time scales - a shorter one (<1s) associated with moment-to-moment orienting of selective visuospatial attention, and a longer one (>10s) associated with more global aspects of attention-to-task. Given their parallel nature, here we examined whether these comparatively slower fluctuations in task-related attention show the same visual field asymmetry - namely, a right visual field bias - as often reported for selective visual-spatial attention. Participants performed a target detection task at fixation while event-related potentials (ERP) time-locked to task-irrelevant visual probes presented in the left and right visual fields were recorded. At random intervals, participants were asked to report whether they were "on-task" or "mind wandering". Our results demonstrated that sensory attenuation during periods of "mind wandering" relative to "on-task", as measured by the visual P1 ERP component at electrodes sites contralateral to the stimulus, was only observed for probes presented in the left visual field. In contrast, the magnitude of sensory gain in the right visual field was insensitive to whether participants were "on-task" or "mind wandering". Taken together, our results support the notion that task-related attention at longer time scales and spatial attention at shorter time scales affect the same underlying mechanism in visual cortex. PMID:25463137

  7. Effect of visual stimulus using central and peripheral visual field on postural control of normal subjects

    PubMed Central

    Park, Du-Jin

    2016-01-01

    [Purpose] This study investigated the effects of visual stimulus using central and peripheral vision fields on postural control. [Subjects and Methods] The subjects consisted of 40 young adult volunteers (15 males, 25 females) who had been informed of the study purpose and procedure. The subjects were randomly divided into four groups of differing visual stimulus. Each group was given visual intervention in a standing position for 3 minutes. Postural control was evaluated before and after visual intervention. [Results] The results of the functional reach test and body sway test showed significant differences among the four groups. [Conclusion] The two-way peripheral vision-field group showed significantly more body sway after visual intervention than the other three groups. This finding may suggest two-way peripheral vision field is a more effective visual stimulus for training postural control and balance. PMID:27390412

  8. Visualization of 3 Dimensional Seismic Vector Fields

    NASA Astrophysics Data System (ADS)

    McQuinn, E.; Chourasia, A.; Minster, J. H.; Schulze, J.

    2009-12-01

    Earthquake simulations produce vast amounts of surface and volumetric temporal data. We have implemented methods to visualize scalar and vector data that allows comprehension of the large amount of information. We leverage advances in graphics processors to draw oriented and textured geometry interactively. We have developed four glyphs to depict the underlying vector data: spheres, ellipsoids, lines, and voxels. The glyphs can be switched interactively and offer multiple visual representations where each glyph enhances different underlying property. Additionally, we have developed highlighting mechanisms to enhance comprehension of direction of vector data. For instance, a sphere would ordinarily not provide directional cues but with our method of highlight the sphere can indicate the direction. We have also developed interactively tunable methods to resolve occlusion of volumetric data. We present multimodal visual representations that provide an array of interactive and flexible visualization techniques to the scientists for scientific investigation through visualization. The visualization tool can be run on a laptop, desktop or virtual reality (VR) environment. We are leveraging one such state-of-the-art system called “StarCAVE”. The StarCAVE surrounds the user with seamless, immersive and stereoscopic virtual environment. This VR environment provides the capability to view the volumetric data from inside the volume in an immersive manner, which is similar to witnessing the earthquake event from inside earth from any vantage point. Interactive visualization of the Terashake simulation allows scientists to flexibly explore existing data intuitively. This is a crop of the Terashake simulation containing the San Andreas near San Bernadino. Color represents velocity magnitude, while direction is that of the displacement vector.

  9. Functional organization of telencephalic visual association fields in pigeons.

    PubMed

    Stacho, Martin; Ströckens, Felix; Xiao, Qian; Güntürkün, Onur

    2016-04-15

    Birds show remarkable visual abilities that surpass most of our visual psychophysiological abilities. In this study, we investigated visual associative areas of the tectofugal visual system in pigeons. Similar to the condition in mammals, ascending visual pathways in birds are subdivided into parallel form/color vs. motion streams at the thalamic and primary telencephalic level. However, we know practically nothing about the functional organization of those telencephalic areas that receive input from the primary visual telencephalic fields. The current study therefore had two objectives: first, to reveal whether these visual associative areas of the tectofugal system are activated during visual discrimination tasks; second, to test whether separated form/color vs. motion pathways can be discerned among these association fields. To this end, we trained pigeons to discriminate either form/color or motion stimuli and used the immediate early gene protein ZENK to capture the activity of the visual associative areas during the task. We could indeed identify several visual associative telencephalic structures by activity pattern changes during discriminations. However, none of these areas displayed a difference between form/color vs. motion sessions. The presence of such a distinction in thalamo-telencephalic, but not in further downstream visual association areas opens the possibility that these separate streams converge very early in birds, which possibly minimizes long-range connections due to the evolutionary pressure toward miniaturized brains. PMID:26802723

  10. Location memory biases reveal the challenges of coordinating visual and kinesthetic reference frames

    PubMed Central

    Simmering, Vanessa R.; Peterson, Clayton; Darling, Warren; Spencer, John P.

    2008-01-01

    Five experiments explored the influence of visual and kinesthetic/proprioceptive reference frames on location memory. Experiments 1 and 2 compared visual and kinesthetic reference frames in a memory task using visually-specified locations and a visually-guided response. When the environment was visible, results replicated previous findings of biases away from the midline symmetry axis of the task space, with stability for targets aligned with this axis. When the environment was not visible, results showed some evidence of bias away from a kinesthetically-specified midline (trunk anterior–posterior [a–p] axis), but there was little evidence of stability when targets were aligned with body midline. This lack of stability may reflect the challenges of coordinating visual and kinesthetic information in the absence of an environmental reference frame. Thus, Experiments 3–5 examined kinesthetic guidance of hand movement to kinesthetically-defined targets. Performance in these experiments was generally accurate with no evidence of consistent biases away from the trunk a–p axis. We discuss these results in the context of the challenges of coordinating reference frames within versus between multiple sensori-motor systems. PMID:17703284

  11. Temperature compensated current sensor using reference magnetic field

    DOEpatents

    Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

    2007-10-09

    A method is described to provide temperature compensation and self-calibration of a current sensor based on a plurality of magnetic field sensors positioned around a current carrying conductor. A reference magnetic field generated within the current sensor housing is detected by a separate but identical magnetic field sensor and is used to correct variations in the output signal due to temperature variations and aging.

  12. Topiramate associated non-glaucomatous visual field defects.

    PubMed

    Haque, Sameen; Shaffi, Mohamed; Tang, Kong C

    2016-09-01

    We report a 34-years-old woman who presented with bilateral incongruous inferior visual field defects after the commencement of topiramate for management of migraine. Investigations did not reveal any underlying angle closure glaucoma, reported in current literature to be associated commonly with topiramate associated visual field defects. The changes in the peripheral visual fields gradually improved over several months after the medication was withdrawn. There were only minor changes persistent on the left side on a background of pre-existing myopia and keratoconus. Visual field deficits secondary to topiramate are more commonly attributed to angle closure glaucoma due to ciliochoroidal effusion syndrome. In such instance, the visual field defects are associated with considerable pain due to raised intra-ocular pressure. There have also been reports of visual scotomas due to retinal damage and maculopathy in patients taking topiramate. It is worthwhile to obtain a baseline perimetry in patients being considered for topiramate therapy in order to gauge any changes in their peripheral field of vision during the treatment. Changes in visual fields during the course of medication use and after cessation can be easily compared especially if there are other possible confounders such as refractive errors or a history of migraine. PMID:27229356

  13. Large Field Visualization with Demand-Driven Calculation

    NASA Technical Reports Server (NTRS)

    Moran, Patrick J.; Henze, Chris

    1999-01-01

    We present a system designed for the interactive definition and visualization of fields derived from large data sets: the Demand-Driven Visualizer (DDV). The system allows the user to write arbitrary expressions to define new fields, and then apply a variety of visualization techniques to the result. Expressions can include differential operators and numerous other built-in functions, ail of which are evaluated at specific field locations completely on demand. The payoff of following a demand-driven design philosophy throughout becomes particularly evident when working with large time-series data, where the costs of eager evaluation alternatives can be prohibitive.

  14. Visualization of Force Fields in Protein Structure Prediction

    SciTech Connect

    Crawford, Clark; Kreylos, Oliver; Hamann, Bernd; Crivelli, Silvia

    2005-04-26

    The force fields used in molecular computational biology are not mathematically defined in such a way that their mathematical representation would facilitate the straightforward application of volume visualization techniques. To visualize energy, it is necessary to define a spatial mapping for these fields. Equipped with such a mapping, we can generate volume renderings of the internal energy states in a molecule. We describe our force field, the spatial mapping that we used for energy, and the visualizations that we produced from this mapping. We provide images and animations that offer insight into the computational behavior of the energy optimization algorithms that we employ.

  15. Animation of orthogonal texture patterns for vector field visualization.

    PubMed

    Bachthaler, Sven; Weiskopf, Daniel

    2008-01-01

    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

  16. Reference Valence Effects of Affective S–R Compatibility: Are Visual and Auditory Results Consistent?

    PubMed Central

    Xiaojun, Zhao; Xuqun, You; Changxiu, Shi; Shuoqiu, Gan; Chaoyi, Hu

    2014-01-01

    Humans may be faster to avoid negative words than to approach negative words, and faster to approach positive words than to avoid positive words. That is an example of affective stimulus–response (S–R) compatibility. The present study identified the reference valence effects of affective stimulus–response (S–R) compatibility when auditory stimulus materials are used. The researchers explored the reference valence effects of affective S–R compatibility using a mixed-design experiment based on visual words, visual pictures and audition. The study computed the average compatibility effect size. A t-test based on visual pictures showed that the compatibility effect size was significantly different from zero, t (22) = 2.43, p<.05 (M = 485 ms). Smaller compatibility effects existed when switching the presentation mode from visual stimuli to auditory stimuli. This study serves as an important reference for the auditory reference valence effects of affective S–R compatibility. PMID:24743797

  17. Blindness and Visual Impairments: Information and Advocacy Organizations. Reference Circular No. 96-01.

    ERIC Educational Resources Information Center

    Library of Congress, Washington, DC. National Library Service for the Blind and Physically Handicapped.

    This reference circular lists organizations that provide a variety of direct services to persons who are blind and visually impaired, including advocacy and advisory services, information and consultation, counseling and employment programs, assistive devices, and publications in special format. Many of the organizations offer guidance to families…

  18. Blindness and Visual Impairments: Information and Advocacy Organizations. Reference Circular No. 01-01.

    ERIC Educational Resources Information Center

    Library of Congress, Washington, DC. National Library Service for the Blind and Physically Handicapped.

    The organizations listed in this reference circular provide a variety of direct services to persons who are blind and visually impaired, including advocacy and advisory services, information and referral, counseling and employment programs, assistive devices, and publications in special format. Many of the organizations also offer guidance to…

  19. EEG can Track the Time Course of Successful Reference Resolution in Small Visual Worlds

    PubMed Central

    Brodbeck, Christian; Gwilliams, Laura; Pylkkänen, Liina

    2015-01-01

    Previous research has shown that language comprehenders resolve reference quickly and incrementally, but not much is known about the neural processes and representations that are involved. Studies of visual short-term memory suggest that access to the representation of an item from a previously seen display is associated with a negative evoked potential at posterior electrodes contralateral to the spatial location of that item in the display. In this paper we demonstrate that resolving the reference of a noun phrase in a recently seen visual display is associated with an event-related potential that is analogous to this effect. Our design was adapted from the visual world paradigm: in each trial, participants saw a display containing three simple objects, followed by a question about the objects, such as Was the pink fish next to a boat?, presented word by word. Questions differed in whether the color adjective allowed the reader to identify the referent of the noun phrase or not (i.e., whether one or more objects of the named color were present). Consistent with our hypothesis, we observed that reference resolution by the adjective was associated with a negative evoked potential at posterior electrodes contralateral to spatial location of the referent, starting approximately 333 ms after the onset of the adjective. The fact that the laterality of the effect depended upon the location of the referent within the display suggests that reference resolution in visual domains involves, at some level, a modality-specific representation. In addition, the effect gives us an estimate of the time course of processing from perception of the written word to the point at which its meaning is brought into correspondence with the referential domain. PMID:26635689

  20. Visual verification of linac light and radiation fields coincidence

    SciTech Connect

    Monti, Angelo F.; Frigerio, Milena; Frigerio, Giovanna

    2003-06-30

    X-ray and light field alignment evaluation is carried out during linac quality assurance programs. In this paper, we compare the size of the light field measured by a photodiode and by a more traditional visual observation with the size of the x-ray field. The comparison between actual light field size, measured with the photodiode, and light field size measured by human eye allow us to verify the reliability of human eye in the evaluation of this parameter. The visual field is always larger than real light field; however, it agrees better with the x-ray field. It matches the light field if we take into account the 25% ({+-} 1%) of the decrement line of the maximum central lightening; however, this method simulates better the actual field employed in radiation treatments.

  1. [Diagnostic difficulties in a case of constricted tubular visual field].

    PubMed

    Dogaru, Oana-Mihaela; Rusu, Monica; Hâncu, Dacia; Horvath, Kárin

    2013-01-01

    In the paper below we present the clinical case of a 48 year old female with various symptoms associated with functional visual disturbance -constricted tubular visual fields, wich lasts from 6 years; the extensive clinical and paraclinical ophthalmological investigations ruled out the presence of an organic disorder. In the present, we suspect a diagnosis of hysteria, still uncertain, wich represented over time a big challenge in psychology and ophthalmology. The mechanisms and reasons for hysteria are still not clear and it could represent a fascinating research theme. The tunnel, spiral or star-shaped visual fields are specific findings in hysteria for patients who present visual disturbance. The question of whether or not a patient with hysterical visual impairment can or cannot "see" is still unresolved. PMID:24701812

  2. Lateralized visual behavior in bottlenose dolphins (Tursiops truncatus) performing audio-visual tasks: the right visual field advantage.

    PubMed

    Delfour, F; Marten, K

    2006-01-10

    Analyzing cerebral asymmetries in various species helps in understanding brain organization. The left and right sides of the brain (lateralization) are involved in different cognitive and sensory functions. This study focuses on dolphin visual lateralization as expressed by spontaneous eye preference when performing a complex cognitive task; we examine lateralization when processing different visual stimuli displayed on an underwater touch-screen (two-dimensional figures, three-dimensional figures and dolphin/human video sequences). Three female bottlenose dolphins (Tursiops truncatus) were submitted to a 2-, 3- or 4-, choice visual/auditory discrimination problem, without any food reward: the subjects had to correctly match visual and acoustic stimuli together. In order to visualize and to touch the underwater target, the dolphins had to come close to the touch-screen and to position themselves using monocular vision (left or right eye) and/or binocular naso-ventral vision. The results showed an ability to associate simple visual forms and auditory information using an underwater touch-screen. Moreover, the subjects showed a spontaneous tendency to use monocular vision. Contrary to previous findings, our results did not clearly demonstrate right eye preference in spontaneous choice. However, the individuals' scores of correct answers were correlated with right eye vision, demonstrating the advantage of this visual field in visual information processing and suggesting a left hemispheric dominance. We also demonstrated that the nature of the presented visual stimulus does not seem to have any influence on the animals' monocular vision choice. PMID:16246503

  3. RF Field Visualization of RF Ablation at the Larmor Frequency

    PubMed Central

    Stang, Pascal; Kerr, Adam; Pauly, John; Scott, Greig

    2012-01-01

    Radiofrequency ablation is an effective minimally invasive treatment for tumors. One primary source of difficulty is monitoring and controlling the ablation region. Currently, RF ablation is performed at 460 kHz, for which MRI could play a role given its capability for temperature monitoring and tumor visualization. If instead the ablation were to be performed at the MRI Larmor frequency, then the MR capability for B1 field mapping could be used to directly visualize the RF fields created by the ablation currents. Visualizing the RF fields may enable better control of the ablation currents, enabling better control of lesion shape and size and improving repeatability. We demonstrate the feasibility of performing RF ablations at 64 MHz and show preliminary results from imaging the RF fields from the ablation. The post-ablation RF fields show an increase in current density in the ablated region, consistent with an increase in conductivity of the ablated tissue. PMID:21775256

  4. Recognizing patterns of visual field loss using unsupervised machine learning

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  5. Spatiotemporal structure of visual receptive fields in macaque superior colliculus.

    PubMed

    Churan, Jan; Guitton, Daniel; Pack, Christopher C

    2012-11-01

    Saccades are useful for directing the high-acuity fovea to visual targets that are of behavioral relevance. The selection of visual targets for eye movements involves the superior colliculus (SC), where many neurons respond to visual stimuli. Many of these neurons are also activated before and during saccades of specific directions and amplitudes. Although the role of the SC in controlling eye movements has been thoroughly examined, far less is known about the nature of the visual responses in this area. We have, therefore, recorded from neurons in the intermediate layers of the macaque SC, while using a sparse-noise mapping procedure to obtain a detailed characterization of the spatiotemporal structure of visual receptive fields. We find that SC responses to flashed visual stimuli start roughly 50 ms after the onset of the stimulus and last for on average ~70 ms. About 50% of these neurons are strongly suppressed by visual stimuli flashed at certain locations flanking the excitatory center, and the spatiotemporal pattern of suppression exerts a predictable influence on the timing of saccades. This suppression may, therefore, contribute to the filtering of distractor stimuli during target selection. We also find that saccades affect the processing of visual stimuli by SC neurons in a manner that is quite similar to the saccadic suppression and postsaccadic enhancement that has been observed in the cortex and in perception. However, in contrast to what has been observed in the cortex, decreased visual sensitivity was generally associated with increased firing rates, while increased sensitivity was associated with decreased firing rates. Overall, these results suggest that the processing of visual stimuli by SC receptive fields can influence oculomotor behavior and that oculomotor signals originating in the SC can shape perisaccadic visual perception. PMID:22933722

  6. Visual Experience Determines the Use of External Reference Frames in Joint Action Control

    PubMed Central

    Dolk, Thomas; Liepelt, Roman; Prinz, Wolfgang; Fiehler, Katja

    2013-01-01

    Vision plays a crucial role in human interaction by facilitating the coordination of one's own actions with those of others in space and time. While previous findings have demonstrated that vision determines the default use of reference frames, little is known about the role of visual experience in coding action-space during joint action. Here, we tested if and how visual experience influences the use of reference frames in joint action control. Dyads of congenitally-blind, blindfolded-sighted, and seeing individuals took part in an auditory version of the social Simon task, which required each participant to respond to one of two sounds presented to the left or right of both participants. To disentangle the contribution of external—agent-based and response-based—reference frames during joint action, participants performed the task with their respective response (right) hands uncrossed or crossed over one another. Although the location of the auditory stimulus was completely task-irrelevant, participants responded overall faster when the stimulus location spatially corresponded to the required response side than when they were spatially non-corresponding: a phenomenon known as the social Simon effect (SSE). In sighted participants, the SSE occurred irrespective of whether hands were crossed or uncrossed, suggesting the use of external, response-based reference frames. Congenitally-blind participants also showed an SSE, but only with uncrossed hands. We argue that congenitally-blind people use both agent-based and response-based reference frames resulting in conflicting spatial information when hands are crossed and, thus, canceling out the SSE. These results imply that joint action control functions on the basis of external reference frames independent of the presence or (transient/permanent) absence of vision. However, the type of external reference frames used for organizing motor control in joint action seems to be determined by visual experience. PMID

  7. Testing of Visual Field with Virtual Reality Goggles in Manual and Visual Grasp Modes

    PubMed Central

    Wroblewski, Dariusz; Francis, Brian A.; Sadun, Alfredo; Vakili, Ghazal; Chopra, Vikas

    2014-01-01

    Automated perimetry is used for the assessment of visual function in a variety of ophthalmic and neurologic diseases. We report development and clinical testing of a compact, head-mounted, and eye-tracking perimeter (VirtualEye) that provides a more comfortable test environment than the standard instrumentation. VirtualEye performs the equivalent of a full threshold 24-2 visual field in two modes: (1) manual, with patient response registered with a mouse click, and (2) visual grasp, where the eye tracker senses change in gaze direction as evidence of target acquisition. 59 patients successfully completed the test in manual mode and 40 in visual grasp mode, with 59 undergoing the standard Humphrey field analyzer (HFA) testing. Large visual field defects were reliably detected by VirtualEye. Point-by-point comparison between the results obtained with the different modalities indicates: (1) minimal systematic differences between measurements taken in visual grasp and manual modes, (2) the average standard deviation of the difference distributions of about 5 dB, and (3) a systematic shift (of 4–6 dB) to lower sensitivities for VirtualEye device, observed mostly in high dB range. The usability survey suggested patients' acceptance of the head-mounted device. The study appears to validate the concepts of a head-mounted perimeter and the visual grasp mode. PMID:25050326

  8. Torsional ARC Effectively Expands the Visual Field in Hemianopia

    PubMed Central

    Satgunam, PremNandhini; Peli, Eli

    2012-01-01

    Purpose Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonios anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion we documented torsional strabismus and torsional HARC. Methods Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter (DVF). The DVF was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared to that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. Results Torsional ARC documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit. Conclusions Torsional strabismus with ARC, when occurring with homonymous hemianopia provides useful field expansion in the lower and upper fields. Dichoptic perimetry permits documentation of ocular alignment (lateral, vertical and torsional) and perceived visual direction under binocular and monocular viewing conditions. Evaluating patients with congenital or early strabismus for HARC is useful when considering surgical correction, particularly in the presence of congenital homonymous hemianopia. PMID:22885782

  9. Sensitivity to the visual field origin of natural image patches in human low-level visual cortex

    PubMed Central

    2015-01-01

    Asymmetries in the response to visual patterns in the upper and lower visual fields (above and below the centre of gaze) have been associated with ecological factors relating to the structure of typical visual environments. Here, we investigated whether the content of the upper and lower visual field representations in low-level regions of human visual cortex are specialised for visual patterns that arise from the upper and lower visual fields in natural images. We presented image patches, drawn from above or below the centre of gaze of an observer navigating a natural environment, to either the upper or lower visual fields of human participants (n = 7) while we used functional magnetic resonance imaging (fMRI) to measure the magnitude of evoked activity in the visual areas V1, V2, and V3. We found a significant interaction between the presentation location (upper or lower visual field) and the image patch source location (above or below fixation); the responses to lower visual field presentation were significantly greater for image patches sourced from below than above fixation, while the responses in the upper visual field were not significantly different for image patches sourced from above and below fixation. This finding demonstrates an association between the representation of the lower visual field in human visual cortex and the structure of the visual input that is likely to be encountered below the centre of gaze. PMID:26131378

  10. Visual Sample Plan (VSP) - FIELDS Integration

    SciTech Connect

    Pulsipher, Brent A.; Wilson, John E.; Gilbert, Richard O.; Hassig, Nancy L.; Carlson, Deborah K.; Bing-Canar, John; Cooper, Brian; Roth, Chuck

    2003-04-19

    Two software packages, VSP 2.1 and FIELDS 3.5, are being used by environmental scientists to plan the number and type of samples required to meet project objectives, display those samples on maps, query a database of past sample results, produce spatial models of the data, and analyze the data in order to arrive at defensible decisions. VSP 2.0 is an interactive tool to calculate optimal sample size and optimal sample location based on user goals, risk tolerance, and variability in the environment and in lab methods. FIELDS 3.0 is a set of tools to explore the sample results in a variety of ways to make defensible decisions with quantified levels of risk and uncertainty. However, FIELDS 3.0 has a small sample design module. VSP 2.0, on the other hand, has over 20 sampling goals, allowing the user to input site-specific assumptions such as non-normality of sample results, separate variability between field and laboratory measurements, make two-sample comparisons, perform confidence interval estimation, use sequential search sampling methods, and much more. Over 1,000 copies of VSP are in use today. FIELDS is used in nine of the ten U.S. EPA regions, by state regulatory agencies, and most recently by several international countries. Both software packages have been peer-reviewed, enjoy broad usage, and have been accepted by regulatory agencies as well as site project managers as key tools to help collect data and make environmental cleanup decisions. Recently, the two software packages were integrated, allowing the user to take advantage of the many design options of VSP, and the analysis and modeling options of FIELDS. The transition between the two is simple for the user – VSP can be called from within FIELDS, automatically passing a map to VSP and automatically retrieving sample locations and design information when the user returns to FIELDS. This paper will describe the integration, give a demonstration of the integrated package, and give users download

  11. Use of computer graphics for visualization of flow fields

    NASA Technical Reports Server (NTRS)

    Watson, Val; Buning, Pieter; Choi, Diana; Bancroft, Gordon; Merritt, Fergus; Rogers, Stuart

    1987-01-01

    A high-performance graphics workstation has been combined with software developed for flow-field visualization to yield a highly effective tool for analysis of fluid-flow dynamics. After the flow fields are obtained from experimental measurements or computer simulations, the workstation permits one to interactively view the dynamics of the flow fields; e.g., the viewer can zoom into a region or rotate his viewing position about the region to study it in more detail. Several techniques for visualization of flow fields with this workstation are described in this paper and illustrated with a videotape available from the authors. The computer hardware and software required to create effective flow visualization displays are discussed. Additional software and hardware required to create videotapes or 16mm movies are also described. Limitations imposed by current workstation performance is addressed and future workstation performance is forecast.

  12. Hierarchical streamline bundles for visualizing 2D flow fields.

    SciTech Connect

    Shene, Ching-Kuang; Wang, Chaoli; Yu, Hongfeng; Chen, Jacqueline H.

    2010-08-01

    We present hierarchical streamline bundles, a new approach to simplifying and visualizing 2D flow fields. Our method first densely seeds a flow field and produces a large number of streamlines that capture important flow features such as critical points. Then, we group spatially neighboring and geometrically similar streamlines to construct a hierarchy from which we extract streamline bundles at different levels of detail. Streamline bundles highlight multiscale flow features and patterns through a clustered yet non-cluttered display. This selective visualization strategy effectively accentuates visual foci and therefore is able to convey the desired insight into the flow fields. The hierarchical streamline bundles we have introduced offer a new way to characterize and visualize the flow structure and patterns in multiscale fashion. Streamline bundles highlight critical points clearly and concisely. Exploring the hierarchy allows a complete visualization of important flow features. Thanks to selective streamline display and flexible LOD refinement, our multiresolution technique is scalable and is promising for viewing large and complex flow fields. In the future, we would like to seek a cost-effective way to generate streamlines without enforcing the dense seeding condition. We will also extend this approach to handle real-world 3D complex flow fields.

  13. International Geomagnetic Reference Field: the 12th generation

    NASA Astrophysics Data System (ADS)

    Thébault, Erwan; Finlay, Christopher C.; Beggan, Ciarán D.; Alken, Patrick; Aubert, Julien; Barrois, Olivier; Bertrand, Francois; Bondar, Tatiana; Boness, Axel; Brocco, Laura; Canet, Elisabeth; Chambodut, Aude; Chulliat, Arnaud; Coïsson, Pierdavide; Civet, François; Du, Aimin; Fournier, Alexandre; Fratter, Isabelle; Gillet, Nicolas; Hamilton, Brian; Hamoudi, Mohamed; Hulot, Gauthier; Jager, Thomas; Korte, Monika; Kuang, Weijia; Lalanne, Xavier; Langlais, Benoit; Léger, Jean-Michel; Lesur, Vincent; Lowes, Frank J.; Macmillan, Susan; Mandea, Mioara; Manoj, Chandrasekharan; Maus, Stefan; Olsen, Nils; Petrov, Valeriy; Ridley, Victoria; Rother, Martin; Sabaka, Terence J.; Saturnino, Diana; Schachtschneider, Reyko; Sirol, Olivier; Tangborn, Andrew; Thomson, Alan; Tøffner-Clausen, Lars; Vigneron, Pierre; Wardinski, Ingo; Zvereva, Tatiana

    2015-05-01

    The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth's magnetic field.

  14. A reference web architecture and patterns for real-time visual analytics on large streaming data

    NASA Astrophysics Data System (ADS)

    Kandogan, Eser; Soroker, Danny; Rohall, Steven; Bak, Peter; van Ham, Frank; Lu, Jie; Ship, Harold-Jeffrey; Wang, Chun-Fu; Lai, Jennifer

    2013-12-01

    Monitoring and analysis of streaming data, such as social media, sensors, and news feeds, has become increasingly important for business and government. The volume and velocity of incoming data are key challenges. To effectively support monitoring and analysis, statistical and visual analytics techniques need to be seamlessly integrated; analytic techniques for a variety of data types (e.g., text, numerical) and scope (e.g., incremental, rolling-window, global) must be properly accommodated; interaction, collaboration, and coordination among several visualizations must be supported in an efficient manner; and the system should support the use of different analytics techniques in a pluggable manner. Especially in web-based environments, these requirements pose restrictions on the basic visual analytics architecture for streaming data. In this paper we report on our experience of building a reference web architecture for real-time visual analytics of streaming data, identify and discuss architectural patterns that address these challenges, and report on applying the reference architecture for real-time Twitter monitoring and analysis.

  15. Graphics and Flow Visualization of Computer Generated Flow Fields

    NASA Technical Reports Server (NTRS)

    Kathong, M.; Tiwari, S. N.

    1987-01-01

    Flow field variables are visualized using color representations described on surfaces that are interpolated from computational grids and transformed to digital images. Techniques for displaying two and three dimensional flow field solutions are addressed. The transformations and the use of an interactive graphics program for CFD flow field solutions, called PLOT3D, which runs on the color graphics IRIS workstation are described. An overview of the IRIS workstation is also described.

  16. Expansion of Severely Constricted Visual Field Using Google Glass.

    PubMed

    Trese, Matthew G J; Khan, Naheed W; Branham, Kari; Conroy, Erin Brown; Moroi, Sayoko E

    2016-05-01

    Google Glass (Google, Mountain View, CA) is a wearable technology with a computer and camera mounted on an eyeglass frame. The camera captures wide-angle video and projects it onto a prism located in the right superior temporal quadrant of the wearer's visual field. The authors present a case of an individual who used Google Glass' video projection feature to expand his severely constricted right visual field. This patient reported improved ambulatory navigation. Using Google Glass, the patient's peripheral vision, measured using Goldmann kinetic perimetry, expanded impressively. Based on these preliminary results, the authors propose further characterization on the potential utility of such head-mount display technology as a tool to improve the lives of patients with severely constricted visual fields. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:486-489.]. PMID:27183556

  17. Visual field influence on manual roll and pitch stabilization

    NASA Technical Reports Server (NTRS)

    Huang, J.-K.; Young, L. R.

    1988-01-01

    Human control performance in nulling perceived tilt angles was investigated for combinations of pseudo-random vestibular disturbances and different waveforms of low frequency wide visual field motions. For both roll and pitch axes, subjects tilted the trainer in which they were seated in the direction of field rotation. This visual bias was much stronger for pitch backwards with upward field rotation. Frequency response analysis showed the dominance of visual cues at low frequencies (below 0.06 Hz) and the reliance on vestibular information in the high frequency range for both axes. Models suggest that operator balancing responses at high frequencies are mainly processed by the semicircular canals rather than the otolith organs. The results also suggest that the subject tends to rely less on the otolith organs for pitch perception than for roll.

  18. Visualizing the blind brain: brain imaging of visual field defects from early recovery to rehabilitation techniques

    PubMed Central

    Urbanski, Marika; Coubard, Olivier A.; Bourlon, Clémence

    2014-01-01

    Visual field defects (VFDs) are one of the most common consequences observed after brain injury, especially after a stroke in the posterior cerebral artery territory. Less frequently, tumors, traumatic brain injury, brain surgery or demyelination can also determine various visual disabilities, from a decrease in visual acuity to cerebral blindness. Visual field defects is a factor of bad functional prognosis as it compromises many daily life activities (e.g., obstacle avoidance, driving, and reading) and therefore the patient’s quality of life. Spontaneous recovery seems to be limited and restricted to the first 6 months, with the best chance of improvement at 1 month. The possible mechanisms at work could be partly due to cortical reorganization in the visual areas (plasticity) and/or partly to the use of intact alternative visual routes, first identified in animal studies and possibly underlying the phenomenon of blindsight. Despite processes of early recovery, which is rarely complete, and learning of compensatory strategies, the patient’s autonomy may still be compromised at more chronic stages. Therefore, various rehabilitation therapies based on neuroanatomical knowledge have been developed to improve VFDs. These use eye-movement training techniques (e.g., visual search, saccadic eye movements), reading training, visual field restitution (the Vision Restoration Therapy, VRT), or perceptual learning. In this review, we will focus on studies of human adults with acquired VFDs, which have used different imaging techniques (Positron Emission Tomography, PET; Diffusion Tensor Imaging, DTI; functional Magnetic Resonance Imaging, fMRI; Magneto Encephalography, MEG) or neurostimulation techniques (Transcranial Magnetic Stimulation, TMS; transcranial Direct Current Stimulation, tDCS) to show brain activations in the course of spontaneous recovery or after specific rehabilitation techniques. PMID:25324739

  19. [Visual fields defects in cerebral hemorrhagic vascular accident].

    PubMed

    Nenciu, A; Stefan, C; Cucea, R; Neacşu, Alina; Balaş, Mihaela; Muşat, Alina; Dachin, Luminiţa; Sîrbu, Carmen

    2003-01-01

    Interpretation of the fields of vision forms a key part of ophthalmic and neurologic examinations. The homonymous hemianopa is a hallmark of a retrochiasmal lesion. Postchiasmal lesions that interrupt the visual pathway may have multiple causes which the circulatory disturbances is one of the most important. The authors present the case of a woman who has an isolated homonymous hemianopa produced by a vascular accident of occipital lobe, dwell upon the only manifestation of the cerebral acute hemorrhagic vascular accident was represented by an visual field defect. PMID:12974025

  20. A reference-free micro defect visualization using pulse laser scanning thermography and image processing

    NASA Astrophysics Data System (ADS)

    Yang, Jinyeol; Choi, Jaemook; Hwang, Soonkyu; An, Yun-Kyu; Sohn, Hoon

    2016-08-01

    As quality control of micro devices and early detection of micro defects in these devices are becoming increasingly important, the demand for a fast and automated online inspection technique to detect micro defects with high spatial resolution is increasing. In this study, a reference-free micro defect visualization algorithm is developed based on laser scanning thermography to detect micro defects in devices instantaneously and automatically with high spatial resolution. A pulse modulated continuous wave laser generates thermal waves in a target device, and the corresponding thermal responses are recorded by an infrared (IR) camera. When the thermal wave encounters a micro defect, the propagation of the thermal wave is blocked at the interface of the micro defect. The blockage of the thermal wave is detected by the proposed reference-free micro defect visualization algorithm. First, an edge detection algorithm is applied to a raw thermal image obtained at a specific time point to extract the thermal discontinuities formed at the boundaries of the defect. The edge images obtained from all time sequences are then assembled into a single accumulated edge image to accentuate defect-induced thermal disturbances in the form of edge features. Finally, the accumulated edge image is automatically processed using a binary imaging algorithm to visualize the micro defect in the target device. The performance of the proposed reference-free micro defect visualization algorithm is examined using two types of specimens, semiconductor chips and ceramic-epoxy composites. The proposed algorithm successfully diagnoses micro defects ranging from 4 μm to 40 μm in width.

  1. Multiresolution and Explicit Methods for Vector Field Analysis and Visualization

    NASA Technical Reports Server (NTRS)

    Nielson, Gregory M.

    1997-01-01

    This is a request for a second renewal (3d year of funding) of a research project on the topic of multiresolution and explicit methods for vector field analysis and visualization. In this report, we describe the progress made on this research project during the second year and give a statement of the planned research for the third year. There are two aspects to this research project. The first is concerned with the development of techniques for computing tangent curves for use in visualizing flow fields. The second aspect of the research project is concerned with the development of multiresolution methods for curvilinear grids and their use as tools for visualization, analysis and archiving of flow data. We report on our work on the development of numerical methods for tangent curve computation first.

  2. Combined influences of gravitoinertial force level and visual field pitch on visually perceived eye level

    NASA Technical Reports Server (NTRS)

    DiZio, P.; Li, W.; Lackner, J. R.; Matin, L.

    1997-01-01

    Psychophysical measurements of the level at which observers set a small visual target so as to appear at eye level (VPEL) were made on 13 subjects in 1.0 g and 1.5 g environments in the Graybiel Laboratory rotating room while they viewed a pitched visual field or while in total darkness. The gravitoinertial force was parallel to the z-axis of the head and body during the measurements. The visual field consisted of two 58 degrees high, luminous, pitched-from-vertical, bilaterally symmetric, parallel lines, viewed in otherwise total darkness. The lines were horizontally separated by 53 degrees and presented at each of 7 angles of pitch ranging from 30 degrees with the top of the visual field turned away from the subject (top backward) to 30 degrees with the top turned toward the subject (top forward). At 1.5 g, VPEL changed linearly with the pitch of the 2-line stimulus and was depressed with top backward pitch and elevated with top forward pitch as had been reported previously at 1.0 g (1,2); however, the slopes of the VPEL-vs-pitch functions at 1.0 g and 1.5 g were indistinguishable. As reported previously also (3,4), the VPEL in darkness was considerably lower at 1.5 g than at 1.0 g; however, although the y-intercept of the VPEL-vs-pitch function in the presence of the 2-line visual field (visual field erect) was also lower at 1.5 g than at 1.0 g as it was in darkness, the G-related difference was significantly attenuated by the presence of the visual field. The quantitative characteristics of the results are consistent with a model in which VPEL is treated as a consequence of an algebraic weighted average or a vector sum of visual and nonvisual influences although the two combining rules lead to fits that are equally good.

  3. Dose homogeneity specification for reference dosimetry of nonstandard fields

    SciTech Connect

    Chung, Eunah; Soisson, Emilie; Seuntjens, Jan

    2012-01-15

    Purpose: To investigate the sensitivity of the plan-class specific correction factor to dose distributions in composite nonstandard field dosimetry. Methods: A cylindrical water-filled PMMA phantom was constructed at the center of which reference absorbed dose could be measured. Ten different TomoTherapy-based IMRT fields were created on the CT images of the phantom. The dose distribution for each IMRT field was estimated at the position of a radiation detector or ionization chamber. The dose in each IMRT field normalized to that in a reference 10 x 10 cm{sup 2} field was measured using a PTW micro liquid ion chamber. Based on the new dosimetry formalism, a plan-class specific correction factor k{sub Q{sub p{sub c{sub s{sub r,Q}{sup f{sub p}{sub c}{sub s}{sub r},f{sub r}{sub e}{sub f}}}}}} for each field was measured for two Farmer-type chambers, Exradin A12 and NE2571, as well as for a smaller Exradin A1SL chamber. The dependence of the measured correction factor on parameters characterizing dose distribution was analyzed. Results: Uncertainty on the plan-class specific correction factor measurement was in the range of 0.3%-0.5% and 0.3%-0.8% for the Farmer-type chambers and the Exradin A1SL, respectively. When the heterogeneity of the central region of the target volume was less than 5%, the correction factor did not differ from unity by more than 0.7% for the three air-filled ionization chambers. For more heterogeneous dose deliveries, the correction factor differed from unity by up to 2.4% for the Farmer-type chambers. For the Exradin A1SL, the correction factor was closer to unity due to the reduced effect of dose gradients, while it was highly variable in different IMRT fields because of a more significant impact of positioning uncertainties on the response of this chamber. Conclusions: The authors have shown that a plan-class specific correction factor can be specified as a function of plan evaluation parameters especially for Farmer-type chambers. This work

  4. Comparison of visual receptive field properties of the superior colliculus and primary visual cortex in rats.

    PubMed

    Li, Xiaoyuan; Sun, Chaokui; Shi, Li

    2015-08-01

    The rat visual system comprises cortical and subcortical pathways. The receptive field properties of cells in the visual cortex have been extensively studied; however, the fundamental roles of the two circuits in visual information processing are not well understood. To address this question, we have applied quantitative methods to compare and characterize the spatiotemporal receptive field (RF) properties of neurons in primary visual cortex (V1) cells and superficial layers of the superior colliculus (SC) in rats by means of extracellular recordings. An analysis of visual stimulus processing revealed distinct functional characteristics of the two visual circuits. RF diameters of SC neurons were significantly larger than those of V1 cells. Most cells in both regions had high orientation selectivity, but the mean orientation bandwidth of the SC was broader than that of V1 cells (101.5° vs. 60.2°). The mean optimal spatial frequency (SF) of SC cells was lower but had a broader bandwidth than that of V1 cells (0.03 vs. 0.068 cpd). The majority of SC and V1 cells (70% and 68%, respectively) had RFs with band-pass temporal frequency (TF) tuning profiles and similar optimal TFs. However, temporal band-pass profiles of the SC showed narrower mean temporal bandwidths than those of V1 cells (1.42 vs. 2.36 octaves). The majority of neurons in visual cortical and subcortical structures were activated in response to high-contrast, drifting gratings in the preferred orientation. The percentage of V1 neurons with a low-contrast threshold was larger than the proportion of SC neurons (45.6% vs. 30%), indicating that the former adapt better to contrast. The substantial overlap in latency distributions between SC and V1 areas suggests that the two visual systems process and analyze visual signals in parallel. However, the two areas use different neural encoding mechanisms based on different latency distribution trends. These results indicate that SC cells have poor spatial acuity

  5. Modified visual field test for ptosis surgery (Leicester Peripheral Field Test)

    PubMed Central

    Ho, S F; Morawski, A; Sampath, R; Burns, J

    2011-01-01

    Introduction There is lack of consensus among Primary Health Care Trusts (PCTs) and health insurers on how to reimburse ptosis surgery and upper lid blepharoplasty, as these procedures can be regarded as cosmetic. Standardised photographs are expensive and difficult to achieve, whilst the routine 24-2 visual field lacks the range to detect visually significant superior field defects. Aim To introduce a modified visual field designed to assess the functional disability associated with ptosis and dermatochalasis and to demonstrate the effectiveness of surgery in improving the visual field. Methods Patients who had surgery for ptosis or dermatochalasis between January 2006 and December 2009 were prospectively invited to perform a modified visual field test pre- and post-operatively. Results In total, 97 patients amounting to 194 eyes were included in the study. Ninety five eyes had aponeurotic repair with or without blepharoplasty and 77 eyes had blepharoplasty alone. This modified test has a sensitivity of 98.8% of detecting ptosis. For patients who underwent ptosis surgery with or without blepharoplasty, 84.2% recorded an improvement in points seen with the test and 81% recorded an improvement in visual field height. For those who had blepharoplasty alone, 90.9% recorded an improvement in points seen in the modified visual field test and 80.6% had improvement in visual field height. Conclusion Our modified visual field assessment is a quick and easy way to assess patient disability associated with ptosis and dermatochalasis. Surgery improves the demonstrated defect, confirming that ptosis and dermatochalasis can be considered a functional rather than cosmetic issue. PMID:21252946

  6. Relationship between visual field loss and contrast threshold elevation in glaucoma

    PubMed Central

    Tochel, CM; Morton, JS; Jay, JL; Morrison, JD

    2005-01-01

    Background There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients. Methods Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg-1 which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20° from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained. Results Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients. Conclusion While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye

  7. The global structure of the visual light field and its relation to the physical light field.

    PubMed

    Kartashova, Tatiana; Sekulovski, Dragan; de Ridder, Huib; Pas, Susan F Te; Pont, Sylvia C

    2016-08-01

    Human observers have been demonstrated to be sensitive to the local (physical) light field, or more precisely, to the primary direction, intensity, and diffuseness of the light at a point in a space. In the present study we focused on the question of whether it is possible to reconstruct the global visual light field, based on observers' inferences of the local light properties. Observers adjusted the illumination on a probe in order to visually fit it in three diversely lit scenes. For each scene they made 36 settings on a regular grid. The global structure of the first order properties of the light field could then indeed be reconstructed by interpolation of light vectors coefficients representing the local settings. We demonstrate that the resulting visual light fields (individual and averaged) can be visualized and we show how they can be compared to physical measurements in the same scenes. Our findings suggest that human observers have a robust impression of the light field that is simplified with respect to the physical light field. In particular, the subtle spatial variations of the physical light fields are largely neglected and the visual light fields were more similar to simple diverging fields than to the actual physical light fields. PMID:27548087

  8. Visual evoked responses to sinusoidal gratings presented in central and right visual fields: I

    SciTech Connect

    George, J.S.; Aine, C.J.; Flynn, E.R.

    1987-01-01

    The present study applies neuromagnetic measurement techniques to probe the neurophysiological processing of spatial frequency (SF) by normal human observers. By exploiting the temporal and spatial resolution of neuromagnetic measurements, we hope to discriminate and characterize underlying neural functions and explore their correlation with perceptual or behavioral performance measures. Spatial frequency analysis has proven a useful paradigm for the study of visual perception and has been applied in psychophysical studies as well as invasive anatomical and physiological studies of experimental animals. These approaches have produced evidence of specialized neural activity and network structure for the analysis of spatial frequency information. Because the encoding of spatial frequency is a function of neuronal receptive-field size and since receptive-field size varies as a function of retinal location, we have also examined effects of visual field on responses to stimuli of defined spatial frequency content. 10 refs., 3 figs.

  9. Visualizing Vector Fields Using Line Integral Convolution and Dye Advection

    NASA Technical Reports Server (NTRS)

    Shen, Han-Wei; Johnson, Christopher R.; Ma, Kwan-Liu

    1996-01-01

    We present local and global techniques to visualize three-dimensional vector field data. Using the Line Integral Convolution (LIC) method to image the global vector field, our new algorithm allows the user to introduce colored 'dye' into the vector field to highlight local flow features. A fast algorithm is proposed that quickly recomputes the dyed LIC images. In addition, we introduce volume rendering methods that can map the LIC texture on any contour surface and/or translucent region defined by additional scalar quantities, and can follow the advection of colored dye throughout the volume.

  10. Reducing Visual Discomfort with HMDs Using Dynamic Depth of Field.

    PubMed

    Carnegie, Kieran; Rhee, Taehyun

    2015-01-01

    Although head-mounted displays (HMDs) are ideal devices for personal viewing of immersive stereoscopic content, exposure to VR applications on them results in significant discomfort for the majority of people, with symptoms including eye fatigue, headaches, nausea, and sweating. A conflict between accommodation and vergence depth cues on stereoscopic displays is a significant cause of visual discomfort. This article describes the results of an evaluation used to judge the effectiveness of dynamic depth-of-field (DoF) blur in an effort to reduce discomfort caused by exposure to stereoscopic content on HMDs. Using a commercial game engine implementation, study participants report a reduction of visual discomfort on a simulator sickness questionnaire when DoF blurring is enabled. The study participants reported a decrease in symptom severity caused by HMD exposure, indicating that dynamic DoF can effectively reduce visual discomfort. PMID:26416360

  11. Visualizing electromagnetic fields at the nanoscale by single molecule localization.

    PubMed

    Steuwe, Christian; Erdelyi, Miklos; Szekeres, G; Csete, M; Baumberg, Jeremy J; Mahajan, Sumeet; Kaminski, Clemens F

    2015-05-13

    Coupling of light to the free electrons at metallic surfaces allows the confinement of electric fields to subwavelength dimensions, far below the optical diffraction limit. While this is routinely used to manipulate light at the nanoscale, in electro-optic devices and enhanced spectroscopic techniques, no characterization technique for imaging the underlying nanoscopic electromagnetic fields exists, which does not perturb the field or employ complex electron beam imaging. Here, we demonstrate the direct visualization of electromagnetic fields on patterned metallic substrates at nanometer resolution, exploiting a strong "autonomous" fluorescence-blinking behavior of single molecules within the confined fields allowing their localization. Use of DNA-constructs for precise positioning of fluorescence dyes on the surface induces this distance-dependent autonomous blinking thus completely obviating the need for exogenous agents or switching methods. Mapping such electromagnetic field distributions at nanometer resolution aids the rational design of nanometals for diverse photonic applications. PMID:25915093

  12. Visualization of geomagnetic field for education and outreach

    NASA Astrophysics Data System (ADS)

    Hatakeyama, T.

    2010-12-01

    Since April 2007 in the project "MAGE" (Mapping Applications to Geomagnetic Environments) we publish tools for visualization of the geomagnetic field on the web. Now five kinds of the geomagnetic field flucuation (from observations and paleomagnetic results) and geodynamo models are freely downloadable from our website, http://mage-p.org/. Access the webpage, download the KML files and open them from Google Earth, then you can experience changing geomagnetic field lines and observations, inclinations, declination, field strength and others, on the Earth's surface. One of our actions in the project is preparation of the documentations of the geomagnetic field and its fluctuations for education and outreach. Especially in Japan, there are poor treatments in the education during elementary and high schools, and the expository writing of the geomagnetic field and concerned articles are also scarce. Moreover, we provide the movie files and stereoscopic visions for the user experiences of the 3D images.

  13. Population receptive field analysis of the primary visual cortex complements perimetry in patients with homonymous visual field defects

    PubMed Central

    Papanikolaou, Amalia; Keliris, Georgios A.; Papageorgiou, T. Dorina; Shao, Yibin; Krapp, Elke; Papageorgiou, Eleni; Stingl, Katarina; Bruckmann, Anna; Schiefer, Ulrich; Logothetis, Nikos K.; Smirnakis, Stelios M.

    2014-01-01

    Injury to the primary visual cortex (V1) typically leads to loss of conscious vision in the corresponding, homonymous region of the contralateral visual hemifield (scotoma). Several studies suggest that V1 is highly plastic after injury to the visual pathways, whereas others have called this conclusion into question. We used functional magnetic resonance imaging (fMRI) to measure area V1 population receptive field (pRF) properties in five patients with partial or complete quadrantic visual field loss as a result of partial V1+ or optic radiation lesions. Comparisons were made with healthy controls deprived of visual stimulation in one quadrant [“artificial scotoma” (AS)]. We observed no large-scale changes in spared-V1 topography as the V1/V2 border remained stable, and pRF eccentricity versus cortical-distance plots were similar to those of controls. Interestingly, three observations suggest limited reorganization: (i) the distribution of pRF centers in spared-V1 was shifted slightly toward the scotoma border in 2 of 5 patients compared with AS controls; (ii) pRF size in spared-V1 was slightly increased in patients near the scotoma border; and (iii) pRF size in the contralesional hemisphere was slightly increased compared with AS controls. Importantly, pRF measurements yield information about the functional properties of spared-V1 cortex not provided by standard perimetry mapping. In three patients, spared-V1 pRF maps overlapped significantly with dense regions of the perimetric scotoma, suggesting that pRF analysis may help identify visual field locations amenable to rehabilitation. Conversely, in the remaining two patients, spared-V1 pRF maps failed to cover sighted locations in the perimetric map, indicating the existence of V1-bypassing pathways able to mediate useful vision. PMID:24706881

  14. Semantic Data And Visualization Techniques Applied To Geologic Field Mapping

    NASA Astrophysics Data System (ADS)

    Houser, P. I. Q.; Royo-Leon, M.; Munoz, R.; Estrada, E.; Villanueva-Rosales, N.; Pennington, D. D.

    2015-12-01

    Geologic field mapping involves the use of technology before, during, and after visiting a site. Geologists utilize hardware such as Global Positioning Systems (GPS) connected to mobile computing platforms such as tablets that include software such as ESRI's ArcPad and other software to produce maps and figures for a final analysis and report. Hand written field notes contain important information and drawings or sketches of specific areas within the field study. Our goal is to collect and geo-tag final and raw field data into a cyber-infrastructure environment with an ontology that allows for large data processing, visualization, sharing, and searching, aiding in connecting field research with prior research in the same area and/or aid with experiment replication. Online searches of a specific field area return results such as weather data from NOAA and QuakeML seismic data from USGS. These results that can then be saved to a field mobile device and searched while in the field where there is no Internet connection. To accomplish this we created the GeoField ontology service using the Web Ontology Language (OWL) and Protégé software. Advanced queries on the dataset can be made using reasoning capabilities can be supported that go beyond a standard database service. These improvements include the automated discovery of data relevant to a specific field site and visualization techniques aimed at enhancing analysis and collaboration while in the field by draping data over mobile views of the site using augmented reality. A case study is being performed at University of Texas at El Paso's Indio Mountains Research Station located near Van Horn, Texas, an active multi-disciplinary field study site. The user can interactively move the camera around the study site and view their data digitally. Geologist's can check their data against the site in real-time and improve collaboration with another person as both parties have the same interactive view of the data.

  15. Categorically distinct types of receptive fields in early visual cortex.

    PubMed

    Talebi, Vargha; Baker, Curtis L

    2016-05-01

    In the visual cortex, distinct types of neurons have been identified based on cellular morphology, response to injected current, or expression of specific markers, but neurophysiological studies have revealed visual receptive field (RF) properties that appear to be on a continuum, with only two generally recognized classes: simple and complex. Most previous studies have characterized visual responses of neurons using stereotyped stimuli such as bars, gratings, or white noise and simple system identification approaches (e.g., reverse correlation). Here we estimate visual RF models of cortical neurons using visually rich natural image stimuli and regularized regression system identification methods and characterize their spatial tuning, temporal dynamics, spatiotemporal behavior, and spiking properties. We quantitatively demonstrate the existence of three functionally distinct categories of simple cells, distinguished by their degree of orientation selectivity (isotropic or oriented) and the nature of their output nonlinearity (expansive or compressive). In addition, these three types have differing average values of several other properties. Cells with nonoriented RFs tend to have smaller RFs, shorter response durations, no direction selectivity, and high reliability. Orientation-selective neurons with an expansive output nonlinearity have Gabor-like RFs, lower spontaneous activity and responsivity, and spiking responses with higher sparseness. Oriented RFs with a compressive nonlinearity are spatially nondescript and tend to show longer response latency. Our findings indicate multiple physiologically defined types of RFs beyond the simple/complex dichotomy, suggesting that cortical neurons may have more specialized functional roles rather than lying on a multidimensional continuum. PMID:26936978

  16. Interactive Visualization of Rotational Symmetry Fields on Surfaces.

    PubMed

    Palacios, Jonathan; Zhang, Eugene

    2011-07-01

    Rotational symmetries (RoSys) have found uses in several computer graphics applications, such as global surface parameterization, geometry remeshing, texture and geometry synthesis, and nonphotorealistic visualization of surfaces. The visualization of N-way rotational symmetry (N-RoSy) fields is a challenging problem due to the ambiguities in the N directions represented by an N-way symmetry. We provide an algorithm that allows faithful and interactive representation of N-RoSy fields in the plane and on surfaces, by adapting the well-known line integral convolution (LIC) technique from vector and second-order tensor fields. Our algorithm captures N directions associated with each point in a given field by decomposing the field into multiple different vector fields, generating LIC images of these fields, and then blending the results. To address the loss of contrast caused by the blending of images, we observe that the pixel values in LIC images closely approximate normally distributed random variables. This allows us to use concepts from probability theory to correct the loss of contrast without the need to perform any image analysis at each frame. PMID:20855918

  17. [How to assess the stability of glaucoma? Visual field].

    PubMed

    Nordmann, J-P

    2006-05-01

    Visual field results are subject to fluctuations in glaucoma and it is important to evaluate them to differentiate fluctuation and progression. Three visual fields are thus required for the determination of progression because of these short or long term fluctuations. During each measurement, some points are tested twice in order to assess short term fluctuation. Other fluctuations are simply due to technical difficulties like a change of position of the head from one examination to the next one. Learning effect is in fact the more important factor which may improve results. However some real long term fluctuations exist, mainly as a function of the general health of the patient. Progression of the visual field is usually assessed by subjective analysis of the fields with an evaluation of the intensity and the size of scotomas and a comparison of global indices. A more objective analysis can be obtain by the use of specific programs like the "Glaucoma Progression Analysis" with the Humphrey Perimeter or the "Progressor" with the Octopus Perimeter. PMID:17072217

  18. The left visual field attentional advantage: No evidence of different speeds of processing across visual hemifields.

    PubMed

    García-Pérez, Miguel A; Alcalá-Quintana, Rocío

    2015-12-01

    Temporal-order judgment (TOJ) and simultaneity judgment (SJ) tasks are used to study differences in speed of processing across sensory modalities, stimulus types, or experimental conditions. Matthews and Welch (2015) reported that observed performance in SJ and TOJ tasks is superior when visual stimuli are presented in the left visual field (LVF) compared to the right visual field (RVF), revealing an LVF advantage presumably reflecting attentional influences. Because observed performance reflects the interplay of perceptual and decisional processes involved in carrying out the tasks, analyses that separate out these influences are needed to determine the origin of the LVF advantage. We re-analyzed the data of Matthews and Welch (2015) using a model of performance in SJ and TOJ tasks that separates out these influences. Parameter estimates capturing the operation of perceptual processes did not differ between hemifields by these analyses, whereas parameter estimates capturing the operation of decisional processes differed. In line with other evidence, perceptual processing also did not differ between SJ and TOJ tasks. Thus, the LVF advantage occurs with identical speeds of processing in both visual hemifields. If attention is responsible for the LVF advantage, it does not exert its influence via prior entry. PMID:26261896

  19. New techniques in 3D scalar and vector field visualization

    SciTech Connect

    Max, N.; Crawfis, R.; Becker, B.

    1993-05-05

    At Lawrence Livermore National Laboratory (LLNL) we have recently developed several techniques for volume visualization of scalar and vector fields, all of which use back-to-front compositing. The first renders volume density clouds by compositing polyhedral volume cells or their faces. The second is a ``splatting`` scheme which composites textures used to reconstruct the scalar or vector fields. One version calculates the necessary texture values in software, and another takes advantage of hardware texture mapping. The next technique renders contour surface polygons using semi-transparent textures, which adjust appropriately when the surfaces deform in a flow, or change topology. The final one renders the ``flow volume`` of smoke or dye tracer swept out by a fluid flowing through a small generating polygon. All of these techniques are applied to a climate model data set, to visualize cloud density and wind velocity.

  20. Patterns in the sky: Natural visualization of aircraft flow fields

    NASA Technical Reports Server (NTRS)

    Campbell, James F.; Chambers, Joseph R.

    1994-01-01

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

  1. Visualizing 3D velocity fields near contour surfaces

    SciTech Connect

    Max, N.; Crawfis, R.; Grant, C.

    1994-03-01

    Vector field rendering is difficult in 3D because the vector icons overlap and hide each other. We propose four different techniques for visualizing vector fields only near surfaces. The first uses motion blurred particles in a thickened region around the surface. The second uses a voxel grid to contain integral curves of the vector field. The third uses many antialiased lines through the surface, and the fourth uses hairs sprouting from the surface and then bending in the direction of the vector field. All the methods use the graphite pipeline, allowing real time rotation and interaction, and the first two methods can animate the texture to move in the flow determined by the velocity field.

  2. Texture splats for 3D vector and scalar field visualization

    SciTech Connect

    Crawfis, R.A.; Max, N.

    1993-04-06

    Volume Visualization is becoming an important tool for understanding large 3D datasets. A popular technique for volume rendering is known as splatting. With new hardware architectures offering substantial improvements in the performance of rendering texture mapped objects, we present textured splats. An ideal reconstruction function for 3D signals is developed which can be used as a texture map for a splat. Extensions to the basic splatting technique are then developed to additionally represent vector fields.

  3. Neural attractor network for application in visual field data classification

    NASA Astrophysics Data System (ADS)

    Fink, Wolfgang

    2004-07-01

    The purpose was to introduce a novel method for computer-based classification of visual field data derived from perimetric examination, that may act as a ' counsellor', providing an independent 'second opinion' to the diagnosing physician. The classification system consists of a Hopfield-type neural attractor network that obtains its input data from perimetric examination results. An iterative relaxation process determines the states of the neurons dynamically. Therefore, even 'noisy' perimetric output, e.g., early stages of a disease, may eventually be classified correctly according to the predefined idealized visual field defect (scotoma) patterns, stored as attractors of the network, that are found with diseases of the eye, optic nerve and the central nervous system. Preliminary tests of the classification system on real visual field data derived from perimetric examinations have shown a classification success of over 80%. Some of the main advantages of the Hopfield-attractor-network-based approach over feed-forward type neural networks are: (1) network architecture is defined by the classification problem; (2) no training is required to determine the neural coupling strengths; (3) assignment of an auto-diagnosis confidence level is possible by means of an overlap parameter and the Hamming distance. In conclusion, the novel method for computer-based classification of visual field data, presented here, furnishes a valuable first overview and an independent 'second opinion' in judging perimetric examination results, pointing towards a final diagnosis by a physician. It should not be considered a substitute for the diagnosing physician. Thanks to the worldwide accessibility of the Internet, the classification system offers a promising perspective towards modern computer-assisted diagnosis in both medicine and tele-medicine, for example and in particular, with respect to non-ophthalmic clinics or in communities where perimetric expertise is not readily available.

  4. Neural attractor network for application in visual field data classification.

    PubMed

    Fink, Wolfgang

    2004-07-01

    The purpose was to introduce a novel method for computer-based classification of visual field data derived from perimetric examination, that may act as a 'counsellor', providing an independent 'second opinion' to the diagnosing physician. The classification system consists of a Hopfield-type neural attractor network that obtains its input data from perimetric examination results. An iterative relaxation process determines the states of the neurons dynamically. Therefore, even 'noisy' perimetric output, e.g., early stages of a disease, may eventually be classified correctly according to the predefined idealized visual field defect (scotoma) patterns, stored as attractors of the network, that are found with diseases of the eye, optic nerve and the central nervous system. Preliminary tests of the classification system on real visual field data derived from perimetric examinations have shown a classification success of over 80%. Some of the main advantages of the Hopfield-attractor-network-based approach over feed-forward type neural networks are: (1) network architecture is defined by the classification problem; (2) no training is required to determine the neural coupling strengths; (3) assignment of an auto-diagnosis confidence level is possible by means of an overlap parameter and the Hamming distance. In conclusion, the novel method for computer-based classification of visual field data, presented here, furnishes a valuable first overview and an independent 'second opinion' in judging perimetric examination results, pointing towards a final diagnosis by a physician. It should not be considered a substitute for the diagnosing physician. Thanks to the worldwide accessibility of the Internet, the classification system offers a promising perspective towards modern computer-assisted diagnosis in both medicine and tele-medicine, for example and in particular, with respect to non-ophthalmic clinics or in communities where perimetric expertise is not readily available

  5. Invariance of visual operations at the level of receptive fields.

    PubMed

    Lindeberg, Tony

    2013-01-01

    The brain is able to maintain a stable perception although the visual stimuli vary substantially on the retina due to geometric transformations and lighting variations in the environment. This paper presents a theory for achieving basic invariance properties already at the level of receptive fields. Specifically, the presented framework comprises (i) local scaling transformations caused by objects of different size and at different distances to the observer, (ii) locally linearized image deformations caused by variations in the viewing direction in relation to the object, (iii) locally linearized relative motions between the object and the observer and (iv) local multiplicative intensity transformations caused by illumination variations. The receptive field model can be derived by necessity from symmetry properties of the environment and leads to predictions about receptive field profiles in good agreement with receptive field profiles measured by cell recordings in mammalian vision. Indeed, the receptive field profiles in the retina, LGN and V1 are close to ideal to what is motivated by the idealized requirements. By complementing receptive field measurements with selection mechanisms over the parameters in the receptive field families, it is shown how true invariance of receptive field responses can be obtained under scaling transformations, affine transformations and Galilean transformations. Thereby, the framework provides a mathematically well-founded and biologically plausible model for how basic invariance properties can be achieved already at the level of receptive fields and support invariant recognition of objects and events under variations in viewpoint, retinal size, object motion and illumination. The theory can explain the different shapes of receptive field profiles found in biological vision, which are tuned to different sizes and orientations in the image domain as well as to different image velocities in space-time, from a requirement that the

  6. Neutron Reference Benchmark Field Specification: ACRR Free-Field Environment (ACRR-FF-CC-32-CL).

    SciTech Connect

    Vega, Richard Manuel; Parma, Edward J.; Griffin, Patrick J.; Vehar, David W.

    2015-07-01

    This report was put together to support the International Atomic Energy Agency (IAEA) REAL- 2016 activity to validate the dosimetry community’s ability to use a consistent set of activation data and to derive consistent spectral characterizations. The report captures details of integral measurements taken in the Annular Core Research Reactor (ACRR) central cavity free-field reference neutron benchmark field. The field is described and an “a priori” calculated neutron spectrum is reported, based on MCNP6 calculations, and a subject matter expert (SME) based covariance matrix is given for this “a priori” spectrum. The results of 31 integral dosimetry measurements in the neutron field are reported.

  7. The role of the brain's frontal eye fields in constructing frame of reference.

    PubMed

    Wallentin, Mikkel

    2012-08-01

    Establishing contextual reference during discourse is a vital part of language function. Personal pronouns (e.g., he/she/it) are used to refer to previously experienced objects, utterances and events. These items, however, are often no longer present in the environment and have to be maintained and manipulated in working memory (WM). One aspect of this is the construction of a spatial frame of reference (e.g., "He was in front of it" where "he" is established as figure and "it" is the ground). The WM processes underlying this function may be different from those involved in establishing a non-spatial relation (e.g., "He was older than her"). The brain's frontal eye fields (FEFs), responsible for eye movement control, are known to be involved in processing spatial WM. This paper reviews both functional magnetic resonance imaging experiments and a subsequent behavioral interference study demonstrating a specific role for the FEFs and the brain's eye movement control system in manipulation of WM content for establishing object-centered spatial reference frames during verbally cued recall of recent visual and linguistic experiences. PMID:22806655

  8. Visual navigation in desert ants Cataglyphis fortis: are snapshots coupled to a celestial system of reference?

    PubMed

    Akesson, Susanne; Wehner, Rüdiger

    2002-07-01

    Central-place foraging insects such as desert ants of the genus Cataglyphis use both path integration and landmarks to navigate during foraging excursions. The use of landmark information and a celestial system of reference for nest location was investigated by training desert ants returning from an artificial feeder to find the nest at one of four alternative positions located asymmetrically inside a four-cylinder landmark array. The cylindrical landmarks were all of the same size and arranged in a square, with the nest located in the southeast corner. When released from the compass direction experienced during training (southeast), the ants searched most intensely at the fictive nest position. When instead released from any of the three alternative directions of approach (southwest, northwest or northeast), the same individuals instead searched at two of the four alternative positions by initiating their search at the position closest to the direction of approach when entering the landmark square and then returning to the position at which snapshot, current landmark image and celestial reference information were in register. The results show that, in the ants' visual snapshot memory, a memorized landmark scene can temporarily be decoupled from a memorized celestial system of reference. PMID:12089203

  9. Suitability of the Visual Field Index according to Glaucoma Severity

    PubMed Central

    Sousa, Marina CC; Biteli, Luis G; Maslin, Jessica S; Leite, Mauro T; Prata, Tiago S

    2015-01-01

    ABSTRACT Purpose: To investigate the suitability of the visual field index (VFI) in different degrees of disease severity in glaucoma patients. Methods: In this cross-sectional study, we consecutively enrolled patients with primary open-angle glaucoma and glaucoma suspects (ocular hypertension). All eyes required a reliable standard automated perimetry (SAP) test to be included. Subjects were categorized into five groups based on glaucoma severity using SAP’s mean deviation (MD). To evaluate the correlation among VFI, MD and pattern standard deviation (PSD), a linear regression model was built. To evaluate the nature of the correlation (i.e. linear vs nonlinear), results were plotted in a scatterplot graph. Results: One hundred and twenty-two eyes of 81 patients (mean age, 59.8 ± 14.5 years) were included. A strong, positive association was found between MD and VFI values (R2 = 0.98, p < 0.001), showing a 3.2% reduction in the VFI for each dB loss in the MD index. It was noticed that 15% of eyes with mild glaucoma (average MD of -3.1 dB) had VFI > 99%. Considering only the eyes with mild and moderate damage in the regression, we found a weaker (nonlinear) correlation than the one we found using all eyes (R2 = 0.85, p < 0.001). There was also a significant, nonlinear correlation between VFI and PSD (R2 = 0.85, p < 0.001). Although higher PSD values were found with increasing visual field damage, this initial trend was reversed when VFI became smaller than 50%, approximately. Conclusion: Visual field index had a strong correlation with MD; however, this correlation was weaker in mild disease, as some patients with early disease had very high VFI values (ceiling effect). Therefore, initial deterioration in visual field status (as assessed by MD values) in patients with early disease may not be detectable using the VFI alone. How to cite this article: Sousa MCC, Biteli LG, Dorairaj S, Maslin JS, Leite M, Prata TS. Suitability of the Visual Field Index according to

  10. 3-D Flow Visualization with a Light-field Camera

    NASA Astrophysics Data System (ADS)

    Thurow, B.

    2012-12-01

    Light-field cameras have received attention recently due to their ability to acquire photographs that can be computationally refocused after they have been acquired. In this work, we describe the development of a light-field camera system for 3D visualization of turbulent flows. The camera developed in our lab, also known as a plenoptic camera, uses an array of microlenses mounted next to an image sensor to resolve both the position and angle of light rays incident upon the camera. For flow visualization, the flow field is seeded with small particles that follow the fluid's motion and are imaged using the camera and a pulsed light source. The tomographic MART algorithm is then applied to the light-field data in order to reconstruct a 3D volume of the instantaneous particle field. 3D, 3C velocity vectors are then determined from a pair of 3D particle fields using conventional cross-correlation algorithms. As an illustration of the concept, 3D/3C velocity measurements of a turbulent boundary layer produced on the wall of a conventional wind tunnel are presented. Future experiments are planned to use the camera to study the influence of wall permeability on the 3-D structure of the turbulent boundary layer.Schematic illustrating the concept of a plenoptic camera where each pixel represents both the position and angle of light rays entering the camera. This information can be used to computationally refocus an image after it has been acquired. Instantaneous 3D velocity field of a turbulent boundary layer determined using light-field data captured by a plenoptic camera.

  11. The Effect of Visualization on Field-Dependent and Field-Independent Learners.

    ERIC Educational Resources Information Center

    Al-Saai, Ahmad J.; Dwyer, Francis M.

    1993-01-01

    A study of 279 females at the University of Qatar that received the Group Embedded Figure Test (GEFT) indicated no interaction between learning style (field independent FID/FD field dependent) and three visual treatment types. Findings indicate the possibility of designing instructional materials to reduce achievement differences between FID and…

  12. Three-dimensional imaging in degraded visual field

    NASA Astrophysics Data System (ADS)

    Oran, A.; Ozharar, S.; Ozdur, I.

    2016-04-01

    Imaging at degraded visual environments is one of the biggest challenges in today’s imaging technologies. Especially military and commercial rotary wing aviation is suffering from impaired visual field in sandy, dusty, marine and snowy environments. For example during landing the rotor churns up the particles and creates dense clouds of highly scattering medium, which limits the vision of the pilot and may result in an uncontrolled landing. The vision in such environments is limited because of the high ratio of scattered photons over the ballistic photons which have the image information. We propose to use optical spatial filtering (OSF) method in order to eliminate the scattered photons and only collect the ballistic photons at the receiver. OSF is widely used in microscopy, to the best of our knowledge this will be the first application of OSF for macroscopic imaging. Our experimental results show that most of the scattered photons are eliminated using the spatial filtering in a highly scattering impaired visual field. The results are compared with a standard broad area photo detector which shows the effectiveness of spatial filtering.

  13. A No-Reference Texture Regularity Metric Based on Visual Saliency.

    PubMed

    Varadarajan, Srenivas; Karam, Lina J

    2015-09-01

    This paper presents a no-reference perceptual metric that quantifies the degree of perceived regularity in textures. The metric is based on the similarity of visual attention (VA) of the textural primitives and the periodic spatial distribution of foveated fixation regions throughout the image. A ground-truth eye-tracking database for textures is also generated as part of this paper and is used to evaluate the performance of the most popular VA models. Using the saliency map generated by the best VA model, the proposed texture regularity metric is computed. It is shown through subjective testing that the proposed metric has a strong correlation with the mean opinion score for the perceived regularity of textures. The proposed texture regularity metric can be used to improve the quality and performance of many image processing applications like texture synthesis, texture compression, and content-based image retrieval. PMID:25826803

  14. Visual Field Usage as an Indicator of Right or Left Hemispheric Information Processing of Gifted Students

    ERIC Educational Resources Information Center

    Olson Meredith B.

    1978-01-01

    The relationship of visual field to brain function is examined in research, and the correlation of gifted students' use of visual field of Piagetian theories of formal logical thought is analyzed. (C L)

  15. The Effects of Augmented Levels of Stress on Reaction Time in the Peripheral Visual Field

    ERIC Educational Resources Information Center

    Reynolds, Harriet L.

    1976-01-01

    The purpose of this study was to determine if reaction time in the peripheral visual field and size of the functional visual field were altered by augmented levels of physical stress while performing on a bicycle ergometer. (JD)

  16. Efficient visualization of unsteady and huge scalar and vector fields

    NASA Astrophysics Data System (ADS)

    Vetter, Michael; Olbrich, Stephan

    2016-04-01

    and methods, we are developing a stand-alone post-processor, adding further data structures and mapping algorithms, and cooperating with the ICON developers and users. With the implementation of a DSVR-based post-processor, a milestone was achieved. By using the DSVR post-processor the mentioned 3 processes are completely separated: the data set is processed in a batch mode - e.g. on the same supercomputer, which the data is generated on - and the interactive 3D rendering is done afterwards on the scientist's local system. At the actual status of implementation the DSVR post-processor supports the generation of isosurfaces and colored slicers on volume data set time series based on rectilinear grids as well as the visualization of pathlines on time varying flow fields based on either rectilinear grids or prism grids. The software implementation and evaluation is done on the supercomputers at DKRZ, including scalability tests using ICON output files in NetCDF format. The next milestones will be (a) the in-situ integration of the DSVR library in the ICON model and (b) the implementation of an isosurface algorithm for prism grids.

  17. An Interactive Visual Analytics Framework for Multi-Field Data in a Geo-Spatial Context

    SciTech Connect

    Zhang, Zhiyuan; Tong, Xiaonan; McDonnell, Kevin T.; Zelenyuk, Alla; Imre, D.; Mueller, Klaus

    2013-04-01

    Climate research produces a wealth of multivariate data. These data often have a geospatial reference and so it is of interest to show them within their geospatial context. One can consider this configuration as a multi field visualization problem, where the geospace provides the expanse of the field. However, there is a limit on the amount of multivariate information that can be fit within a certain spatial location, and the use of linked multivari ate information displays has previously been devised to bridge this gap. In this paper we focus on the interactions in the geographical display, present an implementation that uses Google Earth, and demonstrate it within a tightly linked parallel coordinates display. Several other visual representations, such as pie and bar charts are integrated into the Google Earth display and can be interactively manipulated. Further, we also demonstrate new brushing and visualization techniques for parallel coordinates, such as fixedwindow brushing and correlationenhanced display. We conceived our system with a team of climate researchers, who already made a few important discov eries using it. This demonstrates our system’s great potential to enable scientific discoveries, possibly also in oth er domains where data have a geospatial reference.

  18. Simulation and visualization of velocity fields in simple electrokinetic devices

    NASA Astrophysics Data System (ADS)

    Mahanti, Prasun; Taylor, Thomas; Cochran, Douglas; Keebaugh, Michael; Hayes, Mark A.

    2013-12-01

    Capillary electrophoresis and similar techniques which use an electrified contracting-flow interface (gradient elution moving boundary electrophoresis, electrophoretic exclusion, for examples) are widely used, but the detailed flow dynamics and local electric field effects within this zone have only recently been quantitatively investigated. The motivating force behind this work is establishing particle flow based visualization tools enabling advances for arbitrary interfacial designs beyond this traditional flow/electric field interface. These tools work with pre-computed 2-dimensional fundamental interacting fields which govern particle and(or) fluid flow and can now be obtained from various computational fluid dynamics (CFD) software packages. The particle-flow visualization calculations implemented in the tool and are built upon a solid foundation in fluid dynamics. The module developed in here provides a simulated video particle observation tool which generates a fast check for legitimacy. Further, estimating the accuracy and precision of full 2-D and 3-D simulation is notoriously difficult and a centerline estimation is used to quickly and easily quantitate behaviors in support of decision points. This tool and the recent quantitative assessment of particle behavior within the interfacial area have set the stage for new designs which can emphasize advantageous behaviors not offered by the traditional configuration.

  19. Representation of the visual field in the occipital striate cortex.

    PubMed Central

    McFadzean, R; Brosnahan, D; Hadley, D; Mutlukan, E

    1994-01-01

    The representation of the field of vision in the human striate cortex is based on the Holmes map in which about 25% of the surface area of the striate cortex is allocated to the central 15 degrees of vision. Following the introduction of computed tomography of the brain, the accuracy of the Holmes map was apparently confirmed by clinical/radiological correlation, but a revision has been proposed by Horton and Hoyt based on a magnetic resonance imaging study of three patients with visual field defects due to striate lesions. They propose that the central cortical representation of vision occupies a much larger area. This study reviews the perimetric and imaging findings in a larger series of patients with striate cortical disease and provides support for the revised representation. The clinical phenomenon of macular sparing and its relation to representation of the macula at the occipital pole is also discussed. Images PMID:8148333

  20. Upper visual field distractors preferentially bias attention to the left.

    PubMed

    Thomas, Nicole A; Castine, Benjamin R; Loetscher, Tobias; Nicholls, Michael E R

    2015-03-01

    Pseudoneglect is influenced by vertical visual field stimulation, such that attentional biases are stronger for upper space distractors. Leftward biases result from right hemisphere visuospatial processing, and may be accentuated by additional right hemisphere activation during upper space distraction. Three experiments examined potential explanations for this finding. Experiment 1 controlled for perceptual grouping and leftward biases remained stronger in upper space. Experiment 2 used peripheral distractors to eliminate two further potential explanations: centre-of-mass and framing effects. Eye tracking was included to compare overt and covert attention. Findings supported the occurrence of a stronger leftward attentional bias during upper space distraction. Distractors were rarely fixated, suggesting covert attentional mechanisms are preferentially drawn toward upper space distractors. Experiment 3 employed a cueing paradigm that purposefully directed attention away from centre to determine whether pseudoneglect was influenced by overt attentional orienting. Results indicated that when attention was overtly directed away from centre, the strength of pseudoneglect did not differ based on visual field. It is concluded that covert attention toward upper space distractors recruits additional right hemisphere activation, leading existing leftward biases to be accentuated. PMID:25437374

  1. Incorporating Spatial Models in Visual Field Test Procedures

    PubMed Central

    Rubinstein, Nikki J.; McKendrick, Allison M.; Turpin, Andrew

    2016-01-01

    Purpose To introduce a perimetric algorithm (Spatially Weighted Likelihoods in Zippy Estimation by Sequential Testing [ZEST] [SWeLZ]) that uses spatial information on every presentation to alter visual field (VF) estimates, to reduce test times without affecting output precision and accuracy. Methods SWeLZ is a maximum likelihood Bayesian procedure, which updates probability mass functions at VF locations using a spatial model. Spatial models were created from empirical data, computational models, nearest neighbor, random relationships, and interconnecting all locations. SWeLZ was compared to an implementation of the ZEST algorithm for perimetry using computer simulations on 163 glaucomatous and 233 normal VFs (Humphrey Field Analyzer 24-2). Output measures included number of presentations and visual sensitivity estimates. Results There was no significant difference in accuracy or precision of SWeLZ for the different spatial models relative to ZEST, either when collated across whole fields or when split by input sensitivity. Inspection of VF maps showed that SWeLZ was able to detect localized VF loss. SWeLZ was faster than ZEST for normal VFs: median number of presentations reduced by 20% to 38%. The number of presentations was equivalent for SWeLZ and ZEST when simulated on glaucomatous VFs. Conclusions SWeLZ has the potential to reduce VF test times in people with normal VFs, without detriment to output precision and accuracy in glaucomatous VFs. Translational Relevance SWeLZ is a novel perimetric algorithm. Simulations show that SWeLZ can reduce the number of test presentations for people with normal VFs. Since many patients have normal fields, this has the potential for significant time savings in clinical settings. PMID:26981329

  2. Detection of glaucomatous visual field defect using a screening program of Humphrey Field Analyzer.

    PubMed

    Hong, C; Song, K Y; Youn, D H; Park, W H

    1990-06-01

    To evaluate its clinical efficacy, we report the results of Armaly central field screening test in comparison with those of central 30-2 threshold test of Humphrey Field Analyzer. In 83 cases of normotensives, ocular hypertensives, and glaucoma patients with open-angle or narrow-angle enrolled in this study, a total of 143 eyes were examined. Fifty-four out of 61 patients (88.5%) and 73 out of 81 eyes (90.1%) with visual field defects were detected by the Humphrey Field Analyzer screening test. Eight eyes out of 81(9.9%) with visual field defects detected by the screening test were confirmed as false positive. All points of false positive were solitary, which tended to occur more frequently on superior visual field. A false negative of eight eyes out of 62 (12.9%) detected by the screening test was confirmed by the threshold test, which was more frequent on superior field and shown to be located more peripherally from the fixation point. There was no significant difference in either central sensitivity or age of the false positive and negative. PMID:2214247

  3. Visual-field superiority as a function of stimulus type and content.

    PubMed

    Dutta, Tanusree; Mandal, Manas K

    2002-08-01

    The objective of this study was to examine whether hemispheric superiority is determined more by stimulus type (facial, lexical) or content (neutral, emotional). A split, visual-field experiment was designed using a computer-based program with bilateral presentation (left visual-field, right visual-field) for four sets of stimuli: face (neutral, emotional) x word (neutral, emotional), N = 40. The dependent measures were the frequency of correct response and response latency of correct responses. The visual-field effect was nonsignificant for correct responses; however, the interaction of stimulus type x content was found significant. The interaction of visual-field x stimulus type was significant with response time as the dependent measure. Facial stimuli were processed faster in the left visual-field (a right hemispheric function) and lexical stimuli were processed faster in the right visual-field (a left hemispheric function). No hemispheric effect was observed for stimulus content. PMID:12448834

  4. Near-field visualization of plasmonic lenses: an overall analysis of characterization errors

    PubMed Central

    Wang, Jing; Xu, Zongwei; Fang, Fengzhou

    2015-01-01

    Summary Many factors influence the near-field visualization of plasmonic structures that are based on perforated elliptical slits. Here, characterization errors are experimentally analyzed in detail from both fabrication and measurement points of view. Some issues such as geometrical parameter, probe–sample surface interaction, misalignment, stigmation, and internal stress, have influence on the final near-field probing results. In comparison to the theoretical ideal case of near-field probing of the structures, numerical calculation is carried out on the basis of a finite-difference and time-domain (FDTD) algorithm so as to support the error analyses. The analyses performed on the basis of both theoretical calculation and experimental probing can provide a helpful reference for the researchers probing their plasmonic structures and nanophotonic devices. PMID:26665078

  5. Visual field preferences of object analysis for grasping with one hand.

    PubMed

    Le, Ada; Niemeier, Matthias

    2014-01-01

    When we grasp an object using one hand, the opposite hemisphere predominantly guides the motor control of grasp movements (Davare et al., 2007; Rice et al., 2007). However, it is unclear whether visual object analysis for grasp control relies more on inputs (a) from the contralateral than the ipsilateral visual field, (b) from one dominant visual field regardless of the grasping hand, or (c) from both visual fields equally. For bimanual grasping of a single object we have recently demonstrated a visual field preference for the left visual field (Le and Niemeier, 2013a,b), consistent with a general right-hemisphere dominance for sensorimotor control of bimanual grasps (Le et al., 2014). But visual field differences have never been tested for unimanual grasping. Therefore, here we asked right-handed participants to fixate to the left or right of an object and then grasp the object either with their right or left hand using a precision grip. We found that participants grasping with their right hand performed better with objects in the right visual field: maximum grip apertures (MGAs) were more closely matched to the object width and were smaller than for objects in the left visual field. In contrast, when people grasped with their left hand, preferences switched to the left visual field. What is more, MGA scaling with the left hand showed greater visual field differences compared to right-hand grasping. Our data suggest that, visual object analysis for unimanual grasping shows a preference for visual information from the ipsilateral visual field, and that the left hemisphere is better equipped to control grasps in both visual fields. PMID:25324766

  6. Mass Charge Interactions for Visualizing the Quantum Field

    NASA Astrophysics Data System (ADS)

    Baer, Wolfgang

    Our goal is to integrate the objective and subjective aspects of our personal experience into a single complete theory of reality. To further this endeavor we replace elementary particles with elementary events as the building blocks of an event oriented description of that reality. The simplest event in such a conception is an adaptation of A. Wheeler's primitive explanatory--measurement cycle between internal observations experienced by an observer and their assumed physical causes. We will show how internal forces between charge and mass are required to complete the cyclic sequence of activity. This new formulation of internal material is easier to visualize and map to cognitive experiences than current formulations of sub-atomic physics. In our formulation, called Cognitive Action Theory, such internal forces balance the external forces of gravity-inertia and electricity-magnetism. They thereby accommodate outside influences by adjusting the internal structure of material from which all things are composed. Such accommodation is interpreted as the physical implementation of a model of the external physical world in the brain of a cognitive being or alternatively the response mechanism to external influences in the material of inanimate objects. We adopt the deBroglie-Bohm causal interpretation of QT to show that the nature of space in our model is mathematically equivalent to a field of clocks. Within this field small oscillations form deBroglie waves. This interpretation allows us to visualize the underlying structure of empty space with a charge-mass separation field in equilibrium, and objects appearing in space with quantum wave disturbances to that equilibrium occurring inside material. Space is thereby associated with the internal structure of material and quantum mechanics is shown to be, paraphrasing Heisenberg, the physics of the material that knows the world.

  7. FIELD VALIDATION OF EPA (ENVIRONMENTAL PROTECTION AGENCY) REFERENCE METHOD 23

    EPA Science Inventory

    The accuracy and precision of U.S. Environmental Protection Agency Reference Method 23 was evaluated at a trichloroethylene degreasing facility and an ethylene dichloride plant. The method consists of a procedure for obtaining an integrated sample followed by gas chromatographic ...

  8. Characterization of neutron reference fields at US Department of Energy calibration fields.

    PubMed

    Olsher, R H; McLean, T D; Mallett, M W; Seagraves, D T; Gadd, M S; Markham, Robin L; Murphy, R O; Devine, R T

    2007-01-01

    The Health Physics Measurements Group at the Los Alamos National Laboratory (LANL) has initiated a study of neutron reference fields at selected US Department of Energy (DOE) calibration facilities. To date, field characterisation has been completed at five facilities. These fields are traceable to the National Institute for Standards and Technology (NIST) through either a primary calibration of the source emission rate or through the use of a secondary standard. However, neutron spectral variation is caused by factors such as room return, scatter from positioning tables and fixtures, source anisotropy and spectral degradation due to source rabbits and guide tubes. Perturbations from the ideal isotropic point source field may impact the accuracy of instrument calibrations. In particular, the thermal neutron component of the spectrum, while contributing only a small fraction of the conventionally true dose, can contribute a significant fraction of a dosemeter's response with the result that the calibration becomes facility-specific. A protocol has been developed to characterise neutron fields that relies primarily on spectral measurements with the Bubble Technology Industries (BTI) rotating neutron spectrometer (ROSPEC) and the LANL Bonner sphere spectrometer. The ROSPEC measurements were supplemented at several sites by the BTI Simple Scintillation Spectrometer probe, which is designed to extend the ROSPEC upper energy range from 5 to 15 MeV. In addition, measurements were performed with several rem meters and neutron dosemeters. Detailed simulations were performed using the LANL MCNPX Monte Carlo code to calculate the magnitude of source anisotropy and scatter factors. PMID:17496290

  9. Division of labor in frontal eye field neurons during presaccadic remapping of visual receptive fields

    PubMed Central

    Shin, SooYoon

    2012-01-01

    Our percept of visual stability across saccadic eye movements may be mediated by presaccadic remapping. Just before a saccade, neurons that remap become visually responsive at a future field (FF), which anticipates the saccade vector. Hence, the neurons use corollary discharge of saccades. Many of the neurons also decrease their response at the receptive field (RF). Presaccadic remapping occurs in several brain areas including the frontal eye field (FEF), which receives corollary discharge of saccades in its layer IV from a collicular-thalamic pathway. We studied, at two levels, the microcircuitry of remapping in the FEF. At the laminar level, we compared remapping between layers IV and V. At the cellular level, we compared remapping between different neuron types of layer IV. In the FEF in four monkeys (Macaca mulatta), we identified 27 layer IV neurons with orthodromic stimulation and 57 layer V neurons with antidromic stimulation from the superior colliculus. With the use of established criteria, we classified the layer IV neurons as putative excitatory (n = 11), putative inhibitory (n = 12), or ambiguous (n = 4). We found that just before a saccade, putative excitatory neurons increased their visual response at the RF, putative inhibitory neurons showed no change, and ambiguous neurons increased their visual response at the FF. None of the neurons showed presaccadic visual changes at both RF and FF. In contrast, neurons in layer V showed full remapping (at both the RF and FF). Our data suggest that elemental signals for remapping are distributed across neuron types in early cortical processing and combined in later stages of cortical microcircuitry. PMID:22815407

  10. Analysis and visualization of exact solutions to Einstein's field equations

    NASA Astrophysics Data System (ADS)

    Abdelqader, Majd

    Einstein's field equations are extremely difficult to solve, and when solved, the solutions are even harder to understand. In this thesis, two analysis tools are developed to explore and visualize the curvature of spacetimes. The first tool is based on a thorough examination of observer independent curvature invariants constructed from different contractions of the Riemann curvature tensor. These invariants are analyzed through their gradient fields, and attention is given to the resulting flow and critical points. Furthermore, we propose a Newtonian analog to some general relativistic invariants based on the underlying physical meaning of these invariants, where they represent the cumulative tidal and frame-dragging effects of the spacetime. This provides us with a novel and intuitive tool to compare Newtonian gravitational fields to exact solutions of Einstein's field equations on equal footing. We analyze the obscure Curzon-Chazy solution using the new approach, and reveal rich structure that resembles the Newtonian gravitational field of a non-rotating ring, as it has been suspected for decades. Next, we examine the important Kerr solution, which describes the gravitational field of rotating black holes. We discover that the observable part of the geometry outside the black hole's event horizon depends significantly on its angular momentum. The fields representing the cumulative tidal and frame-dragging forces change qualitatively at seven specific values of the dimensionless spin parameter of the black hole. The second tool we develop in this thesis is the accurate construction of the Penrose conformal diagrams. These diagrams are a valuable tool to explore the causal structure of spacetimes, where the entire spacetime is compactified to a finite size, and the coordinate choice is fixed such that light rays are straight lines on the diagram. However, for most spacetimes these diagrams can only be constructed as a qualitative guess, since their null geodesics

  11. Mapping of Visual Receptive Fields by Tomographic Reconstruction

    PubMed Central

    Pipa, Gordon; Chen, Zhe; Neuenschwander, Sergio; Lima, Bruss; Brown, Emery N.

    2014-01-01

    The moving bar experiment is a classic paradigm for characterizing the receptive field (RF) properties of neurons in primary visual cortex (V1). Current approaches for analyzing neural spiking activity recorded from these experiments do not take into account the point process nature of these data and the circular geometry of the stimulus presentation. We present a novel analysis approach to mapping V1 receptive fields that combines point process generalized linear models (PPGLM) with tomographic reconstruction computed by filtered-back projection. We use the method to map the RF sizes and orientations of 251 V1 neurons recorded from two macaque monkeys during a moving bar experiment. Our cross-validated goodness-of-fit analyses show that the PPGLM provides a more accurate characterization of spike train data than analyses based on rate functions computed by the methods of spike triggered averages or first-order Wiener-Volterra kernel. Our analysis leads to a new definition of RF size as the spatial area over which the spiking activity is significantly greater than baseline activity. Our approach yields larger RF sizes and sharper orientation tuning estimates. The tomographic reconstruction paradigm further suggests an efficient approach to choosing the number of directions and the number of trials per direction in designing moving bar experiments. Our results demonstrate that standard tomographic principles for image reconstruction can be adapted to characterize V1 RFs and that two fundamental properties, size and orientation, may be substantially different from what is currently reported. PMID:22734491

  12. Splitting Attention across the Two Visual Fields in Visual Short-Term Memory

    ERIC Educational Resources Information Center

    Delvenne, Jean-Francois; Holt, Jessica L.

    2012-01-01

    Humans have the ability to attentionally select the most relevant visual information from their extrapersonal world and to retain it in a temporary buffer, known as visual short-term memory (VSTM). Research suggests that at least two non-contiguous items can be selected simultaneously when they are distributed across the two visual hemifields. In…

  13. Plate Scattering Visualization: Images, Near Fields, Currents, and Far Field Patterns

    NASA Technical Reports Server (NTRS)

    Shaeffer, John; Hom, Kam

    2004-01-01

    This paper presents a case study of a simple yet robust target for demonstration of the EM visualization process. A five lambda square plate exhibits many scattering mechanisms depending on excitation angle and polarization: specular scattering, leading and trailing edge diffraction, traveling wave, and edge wave scattering. Bistatic k space radiation images, currents maps, and near scattered / total fields are examined for each of these scattering mechanisms.

  14. Visual processing of coherent rotation in the central visual field: an fMRI study.

    PubMed

    Könönen, Mervi; Pääkkönen, Ari; Pihlajamäki, Maija; Partanen, Kaarina; Karjalainen, Pasi A; Soimakallio, Seppo; Aronen, Hannu J

    2003-01-01

    Functional magnetic resonance imaging was used to determine the brain areas that process coherent motion. To reduce the activity related to eye-movement planning and self-motion perception, rotation was used as coherent motion and the stimulus was restricted to the central visual field. Coherent rotation relative to incoherent random-dot motion resulted in consistent activation in the superior parietal lobule (SPL), in the lateral occipital gyrus (presumptive kinetic occipital region, KO), and in the fusiform gyrus (FG). The main novel finding in present study is the bilateral SPL activation, which has not been found in any previous study contrasting coherent and incoherent motion. It is suggested that the SPL activation is related to form-from-motion processing. The stimulus modification that prevented abrupt appearances of dots at the borders of the stimulus field increased the strength of rolling disk-like percept of the coherent stimulus. This perception of form may also be at least partly responsible for the activation in KO and FG. With this explanation, our three consistent activation areas are in line with previous findings. Furthermore, these results demonstrate that even delicate changes in some stimulus aspects can lead to significant changes in the activation of the brain. PMID:14700259

  15. Effects of Field of View and Visual Complexity on Virtual Reality Training Effectiveness for a Visual Scanning Task.

    PubMed

    Ragan, Eric D; Bowman, Doug A; Kopper, Regis; Stinson, Cheryl; Scerbo, Siroberto; McMahan, Ryan P

    2015-07-01

    Virtual reality training systems are commonly used in a variety of domains, and it is important to understand how the realism of a training simulation influences training effectiveness. We conducted a controlled experiment to test the effects of display and scenario properties on training effectiveness for a visual scanning task in a simulated urban environment. The experiment varied the levels of field of view and visual complexity during a training phase and then evaluated scanning performance with the simulator's highest levels of fidelity and scene complexity. To assess scanning performance, we measured target detection and adherence to a prescribed strategy. The results show that both field of view and visual complexity significantly affected target detection during training; higher field of view led to better performance and higher visual complexity worsened performance. Additionally, adherence to the prescribed visual scanning strategy during assessment was best when the level of visual complexity during training matched that of the assessment conditions, providing evidence that similar visual complexity was important for learning the technique. The results also demonstrate that task performance during training was not always a sufficient measure of mastery of an instructed technique. That is, if learning a prescribed strategy or skill is the goal of a training exercise, performance in a simulation may not be an appropriate indicator of effectiveness outside of training-evaluation in a more realistic setting may be necessary. PMID:26357242

  16. Effects of Field of View and Visual Complexity on Virtual Reality Training Effectiveness for a Visual Scanning Task

    DOE PAGESBeta

    Ragan, Eric D.; Bowman, Doug A.; Kopper, Regis; Stinson, Cheryl; Scerbo, Siroberto; McMahan, Ryan P.

    2015-02-13

    Virtual reality training systems are commonly used in a variety of domains, and it is important to understand how the realism of a training simulation influences training effectiveness. The paper presents a framework for evaluating the effects of virtual reality fidelity based on an analysis of a simulation’s display, interaction, and scenario components. Following this framework, we conducted a controlled experiment to test the effects of fidelity on training effectiveness for a visual scanning task. The experiment varied the levels of field of view and visual realism during a training phase and then evaluated scanning performance with the simulator’s highestmore » level of fidelity. To assess scanning performance, we measured target detection and adherence to a prescribed strategy. The results show that both field of view and visual realism significantly affected target detection during training; higher field of view led to better performance and higher visual realism worsened performance. Additionally, the level of visual realism during training significantly affected learning of the prescribed visual scanning strategy, providing evidence that high visual realism was important for learning the technique. The results also demonstrate that task performance during training was not always a sufficient measure of mastery of an instructed technique. That is, if learning a prescribed strategy or skill is the goal of a training exercise, performance in a simulation may not be an appropriate indicator of effectiveness outside of training—evaluation in a more realistic setting may be necessary.« less

  17. Effects of Field of View and Visual Complexity on Virtual Reality Training Effectiveness for a Visual Scanning Task

    SciTech Connect

    Ragan, Eric D.; Bowman, Doug A.; Kopper, Regis; Stinson, Cheryl; Scerbo, Siroberto; McMahan, Ryan P.

    2015-02-13

    Virtual reality training systems are commonly used in a variety of domains, and it is important to understand how the realism of a training simulation influences training effectiveness. The paper presents a framework for evaluating the effects of virtual reality fidelity based on an analysis of a simulation’s display, interaction, and scenario components. Following this framework, we conducted a controlled experiment to test the effects of fidelity on training effectiveness for a visual scanning task. The experiment varied the levels of field of view and visual realism during a training phase and then evaluated scanning performance with the simulator’s highest level of fidelity. To assess scanning performance, we measured target detection and adherence to a prescribed strategy. The results show that both field of view and visual realism significantly affected target detection during training; higher field of view led to better performance and higher visual realism worsened performance. Additionally, the level of visual realism during training significantly affected learning of the prescribed visual scanning strategy, providing evidence that high visual realism was important for learning the technique. The results also demonstrate that task performance during training was not always a sufficient measure of mastery of an instructed technique. That is, if learning a prescribed strategy or skill is the goal of a training exercise, performance in a simulation may not be an appropriate indicator of effectiveness outside of training—evaluation in a more realistic setting may be necessary.

  18. Progress in Scientific Visualization

    SciTech Connect

    Max, N

    2004-11-15

    Visualization of observed data or simulation output is important to science and engineering. I have been particularly interested in visualizing 3-D structures, and report here my personal impressions on progress in the last 20 years in visualizing molecules, scalar fields, and vector fields and their associated flows. I have tried to keep the survey and list of references manageable, so apologize to those authors whose techniques I have not mentioned, or have described without a reference citation.

  19. Frames of Reference for the Light-from-Above Prior in Visual Search and Shape Judgements

    ERIC Educational Resources Information Center

    Adams, Wendy J.

    2008-01-01

    Faced with highly complex and ambiguous visual input, human observers must rely on prior knowledge and assumptions to efficiently determine the structure of their surroundings. One of these assumptions is the "light-from-above" prior. In the absence of explicit light-source information, the visual system assumes that the light-source is roughly…

  20. Attention in Schizophrenia: An Analysis of Selectivity in the Functional Visual Field

    ERIC Educational Resources Information Center

    Cegalis, John A.; And Others

    1977-01-01

    A visual-spatial approach to the study of attention dysfunction was presented. The hypotheses of broadened and narrowed attention were tested by comparing peripheral visual discrimination of acute schizophrenic, chronic schizophrenic, and normal subjects within two regions of the functional visual field. (Editor)

  1. Flow charts: visualization of vector fields on arbitrary surfaces.

    PubMed

    Li, Guo-Shi; Tricoche, Xavier; Weiskopf, Daniel; Hansen, Charles

    2008-01-01

    We introduce a novel flow visualization method called Flow Charts, which uses a texture atlas approach for the visualization of flows defined over curved surfaces. In this scheme the surface and its associated flow are segmented into overlapping patches which are then parameterized and packed in the texture domain. This scheme allows accurate particle advection across multiple charts in the texture domain, providing a flexible framework that supports various flow visualization techniques. The use of surface parameterization enables flow visualization techniques requiring the global view of the surface over long time spans, such as Unsteady Flow LIC (UFLIC), particle-based Unsteady Flow Advection-Convolution (UFAC), or dye advection. It also prevents visual artifacts normally associated with view-dependent methods. Represented as textures, Flow Charts can be naturally integrated into GPU flow visualization techniques for interactive performance. PMID:18599918

  2. Flow Charts: Visualization of Vector Fields on Arbitrary Surfaces

    PubMed Central

    Li, Guo-Shi; Tricoche, Xavier; Weiskopf, Daniel; Hansen, Charles

    2009-01-01

    We introduce a novel flow visualization method called Flow Charts, which uses a texture atlas approach for the visualization of flows defined over curved surfaces. In this scheme, the surface and its associated flow are segmented into overlapping patches, which are then parameterized and packed in the texture domain. This scheme allows accurate particle advection across multiple charts in the texture domain, providing a flexible framework that supports various flow visualization techniques. The use of surface parameterization enables flow visualization techniques requiring the global view of the surface over long time spans, such as Unsteady Flow LIC (UFLIC), particle-based Unsteady Flow Advection Convolution (UFAC), or dye advection. It also prevents visual artifacts normally associated with view-dependent methods. Represented as textures, Flow Charts can be naturally integrated into hardware accelerated flow visualization techniques for interactive performance. PMID:18599918

  3. Response time to colored stimuli in the full visual field

    NASA Technical Reports Server (NTRS)

    Haines, R. F.; Dawson, L. M.; Galvan, T.; Reid, L. M.

    1975-01-01

    Peripheral visual response time was measured in seven dark adapted subjects to the onset of small (45' arc diam), brief (50 msec), colored (blue, yellow, green, red) and white stimuli imaged at 72 locations within their binocular field of view. The blue, yellow, and green stimuli were matched for brightness at about 2.6 sub log 10 units above their absolute light threshold, and they appeared at an unexpected time and location. These data were obtained to provide response time and no-response data for use in various design disciplines involving instrument panel layout. The results indicated that the retina possesses relatively concentric regions within each of which mean response time can be expected to be of approximately the same duration. These regions are centered near the fovea and extend farther horizontally than vertically. Mean foveal response time was fastest for yellow and slowest for blue. Three and one-half percent of the total 56,410 trials presented resulted in no-responses. Regardless of stimulus color, the lowest percentage of no-responses occurred within 30 deg arc from the fovea and the highest within 40 deg to 80 deg arc below the fovea.

  4. Action video game players and deaf observers have larger Goldmann visual fields.

    PubMed

    Buckley, David; Codina, Charlotte; Bhardwaj, Palvi; Pascalis, Olivier

    2010-03-01

    We used Goldmann kinetic perimetry to compare how training and congenital auditory deprivation may affect the size of the visual field. We measured the ability of action video game players and deaf observers to detect small moving lights at various locations in the central (around 30 degrees from fixation) and peripheral (around 60 degrees ) visual fields. Experiment 1 found that 10 habitual video game players showed significantly larger central and peripheral field areas than 10 controls. In Experiment 2 we found that 13 congenitally deaf observers had significantly larger visual fields than 13 hearing controls for both the peripheral and central fields. Here the greatest differences were found in the lower parts of the fields. Comparison of the two groups showed that whereas VGP players have a more uniform increase in field size in both central and peripheral fields deaf observers show non-uniform increases with greatest increases in lower parts of the visual field. PMID:19962395

  5. About the Role of Visual Field Defects in Pure Alexia

    ERIC Educational Resources Information Center

    Pflugshaupt, Tobias; Gutbrod, Klemens; Wurtz, Pascal; von Wartburg, Roman; Nyffeler, Thomas; de Haan, Bianca; Karnath, Hans-Otto; Mueri, Rene M.

    2009-01-01

    Pure alexia is an acquired reading disorder characterized by a disproportionate prolongation of reading time as a function of word length. Although the vast majority of cases reported in the literature show a right-sided visual defect, little is known about the contribution of this low-level visual impairment to their reading difficulties. The…

  6. NAEP and the Visual Arts: Framework, Field Test, and Assessment.

    ERIC Educational Resources Information Center

    Vanneman, Alan; Goodwin, Mac Arthur

    1998-01-01

    The National Assessment of Educational Progress (NAEP) has developed a new generation of assessment tasks for assessing student achievement in the visual arts. Using paper-and-pencil and performance formats, these tasks draw on the concepts, skills, and processes used to create and understand visual images from a variety of world cultures and…

  7. A Study of Peripheral Visual Field Characteristics at Good Prospect Intersection

    NASA Astrophysics Data System (ADS)

    Toyoda, Keiji; Iwai, Naoki; Oyama, Shouta

    This paper shows the basic experiment and simulation about peripheral visual field characteristics as visual factor, two major factors for rural districts accident ((1)collision course relationship, (2)within peripheral visual field), from the stand of view that detects recognizing quantitative threshold for shape change (stimulus) in peripheral visual field. It is understood that critical such dimension as diameter for circle, side length for square, triangle, and oval are important to recognize the right angle direction vehicle. These showed that a similar thing applied even if the aircrafts that moved three-dimensional spaces not only the vehicles in two dimensional planes. This paper made clear the limit of the peripheral visual field characteristics that is one of the human visual characteristics and also showed no dependency on figure shape as long as the maximum side size is the same as the diameter of circle.

  8. Full-reference quality assessment of stereoscopic images by learning binocular receptive field properties.

    PubMed

    Shao, Feng; Li, Kemeng; Lin, Weisi; Jiang, Gangyi; Yu, Mei; Dai, Qionghai

    2015-10-01

    Quality assessment of 3D images encounters more challenges than its 2D counterparts. Directly applying 2D image quality metrics is not the solution. In this paper, we propose a new full-reference quality assessment for stereoscopic images by learning binocular receptive field properties to be more in line with human visual perception. To be more specific, in the training phase, we learn a multiscale dictionary from the training database, so that the latent structure of images can be represented as a set of basis vectors. In the quality estimation phase, we compute sparse feature similarity index based on the estimated sparse coefficient vectors by considering their phase difference and amplitude difference, and compute global luminance similarity index by considering luminance changes. The final quality score is obtained by incorporating binocular combination based on sparse energy and sparse complexity. Experimental results on five public 3D image quality assessment databases demonstrate that in comparison with the most related existing methods, the devised algorithm achieves high consistency with subjective assessment. PMID:26011880

  9. Visual field defects after missile injuries to the geniculo-striate pathway in man.

    NASA Technical Reports Server (NTRS)

    Koerner, F.; Teuber, H.-L.

    1973-01-01

    The main objective of the survey reported was a quantitative comparison of different visual functions at identical retinal points of individual patients. The possibility to develop objective forms of visual-field testing was also explored, taking into account reports by Frydrychowicz and Harms (1940) and Harms (1951). These investigators had insisted that pupillary responses to light are depressed in areas of homonymous scotomata. The shapes of homonymous visual field defects are discussed together with questions regarding the association and dissociation of symptoms.

  10. Characterization of field compaction using shrinkage analysis and visual soil examination

    NASA Astrophysics Data System (ADS)

    Johannes, Alice; Keller, Thomas; Weisskopf, Peter; Schulin, Rainer; Boivin, Pascal

    2016-04-01

    Visual field examination of soil structure can be very useful in extension work, because it is easy to perform, does not require equipment or lab analyses and the result is immediately available. The main limitations of visual methods are subjectivity and variation with field conditions. To provide reliable reference information, methods for objective and quantitative assessment of soil structure quality are still necessary. Soil shrinkage analysis (ShA) (Braudeau et al., 2004) provides relevant parameters for soil functions that allow precise and accurate assessment of soil compaction. To test it, we applied ShA to samples taken from a soil structure observatory (SSO) set up in 2014 on a loamy soil in Zurich, Switzerland to quantify the structural recovery of compacted agricultural soil. The objective in this presentation is to compare the ability of a visual examination method and ShA to assess soil compaction and structural recovery on the SSO field plots. Eighteen undisturbed soil samples were taken in the topsoil (5-10 cm) and 9 samples in the subsoil (30-35 cm) of compacted plots and control. Each sample went through ShA, followed by a visual examination of the sample and analysis of soil organic carbon and texture. ShA combines simultaneous shrinkage with water retention measurements and, in addition to soil properties such as bulk density, coarse and fine porosity, also provides information on hydrostructural stability and plasma and structural porosity. For visual examination the VESS method of Ball et al. (2007) was adapted to core samples previously equilibrated at -100 hPa matric potential. The samples were randomly and anonymously scored to avoid subjectivity and were equilibrated to insure comparable conditions. Compaction decreased the total specific volume, as well as air and water content at all matric potentials. Structural porosity was reduced, while plasma porosity remained unchanged. Compaction also changed the shape of the shrinkage curve: (i

  11. [Particular clinical situations in the glaucoma patient. True or false deterioration of the visual field?].

    PubMed

    Nordmann, J-P

    2004-06-01

    Measurement errors, correction errors, head position errors, changes in strategy, fluctuations. There are many parameters influencing the results of visual field measurement. When in doubt, it is indispensable to repeat the examination before concluding that the results have deteriorated. In addition to the qualitative assessment, the analysis of global indices can pinpoint the degree of visual field deterioration. PMID:15319754

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

    PubMed

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

    2014-07-01

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

  13. Visual Field Asymmetries in Attention Vary with Self-Reported Attention Deficits

    ERIC Educational Resources Information Center

    Poynter, William; Ingram, Paul; Minor, Scott

    2010-01-01

    The purpose of this study was to determine whether an index of self-reported attention deficits predicts the pattern of visual field asymmetries observed in behavioral measures of attention. Studies of "normal" subjects do not present a consistent pattern of asymmetry in attention functions, with some studies showing better left visual field (LVF)…

  14. A Lack of Left Visual Field Bias when Individuals with Autism Process Faces

    ERIC Educational Resources Information Center

    Dundas, Eva M.; Best, Catherine A.; Minshew, Nancy J.; Strauss, Mark S.

    2012-01-01

    It has been established that typically developing individuals have a bias to attend to facial information in the left visual field (LVF) more than in the right visual field. This bias is thought to arise from the right hemisphere's advantage for processing facial information, with evidence suggesting it to be driven by the configural demands of…

  15. Effect of Visual Field Presentation on Action Planning (Estimating Reach) in Children

    ERIC Educational Resources Information Center

    Gabbard, Carl; Cordova, Alberto

    2012-01-01

    In this article, the authors examined the effects of target information presented in different visual fields (lower, upper, central) on estimates of reach via use of motor imagery in children (5-11 years old) and young adults. Results indicated an advantage for estimating reach movements for targets placed in lower visual field (LoVF), with all…

  16. Neural systems involved in processing novel linguistic constructions and their visual referents

    PubMed Central

    Johnson, Matthew A.; Turk-Browne, Nicholas B.; Goldberg, Adele E.

    2016-01-01

    In language, abstract phrasal patterns provide an important source of meaning, but little is known about whether or how such constructions are used to predict upcoming visual scenes. Findings from two fMRI studies indicate that initial exposure to a novel construction allows its semantics to be used for such predictions. Specifically, greater activity in the ventral striatum, a region sensitive to prediction errors, was linked to worse overall comprehension of a novel construction. Moreover, activity in occipital cortex was attenuated when a visual event could be inferred from a learned construction, which may reflect predictive coding of the event. These effects disappeared when predictions were unlikely: that is, when phrases provided no additional information about visual events. These findings support the idea that learners create and evaluate predictions about new instances during comprehension of novel linguistic constructions.

  17. Current State of Digital Reference in Primary and Secondary Education; The Technological Challenges of digital Reference; Question Negotiation and the Technological Environment; Evaluation of Chat Reference Service Quality; Visual Resource Reference: Collaboration between Digital Museums and Digital Libraries.

    ERIC Educational Resources Information Center

    Lankes, R. David; Penka, Jeffrey T.; Janes, Joseph; Silverstein, Joanne; White, Marilyn Domas; Abels, Eileen G.; Kaske, Neal; Goodrum, Abby A.

    2003-01-01

    Includes five articles that discuss digital reference in elementary and secondary education; the need to understand the technological environment of digital reference; question negotiation in digital reference; a pilot study that evaluated chat reference service quality; and collaborative digital museum and digital library reference services. (LRW)

  18. Temperature compensated and self-calibrated current sensor using reference magnetic field

    DOEpatents

    Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

    2007-10-09

    A method is described to provide temperature compensation and self-calibration of a current sensor based on a plurality of magnetic field sensors positioned around a current carrying conductor. A reference magnetic field generated within the current sensor housing is detected by the magnetic field sensors and is used to correct variations in the output signal due to temperature variations and aging.

  19. Behavioral and electrophysiological evidence of opposing lateral visuospatial asymmetries in the upper and lower visual fields.

    PubMed

    Loughnane, Gerard M; Shanley, John P; Lalor, Edmund C; O'Connell, Redmond G

    2015-02-01

    Neurologically healthy individuals typically exhibit a subtle bias towards the left visual field during spatial judgments, known as "pseudoneglect". However, it has yet to be reliably established if the direction and magnitude of this lateral bias varies along the vertical plane. Here, participants were required to distribute their attention equally across a checkerboard array spanning the entire visual field in order to detect transient targets that appeared at unpredictable locations. Reaction times (RTs) were faster to left hemifield targets in the lower visual field but the opposite trend was observed for targets in the upper field. Electroencephalogram (EEG) analyses focused on the interval prior to target onset in order to identify endogenous neural correlates of these behavioral asymmetries. The relative hemispheric distribution of pre-target oscillatory alpha power was predictive of RT bias to targets in the lower visual field but not the upper field, indicating separate attentional mechanisms for the upper and lower visual fields. Analysis of multifocal visual-evoked potentials (MVEP) in the pre-target interval also indicated that the opposing upper and lower field asymmetries may impact on the magnitude of primary visual cortical responses. These results provide new evidence of a functional segregation of upper and lower field visuospatial processing. PMID:25282061

  20. A self-organizing model of perisaccadic visual receptive field dynamics in primate visual and oculomotor system

    PubMed Central

    Mender, Bedeho M. W.; Stringer, Simon M.

    2015-01-01

    We propose and examine a model for how perisaccadic visual receptive field dynamics, observed in a range of primate brain areas such as LIP, FEF, SC, V3, V3A, V2, and V1, may develop through a biologically plausible process of unsupervised visually guided learning. These dynamics are associated with remapping, which is the phenomenon where receptive fields anticipate the consequences of saccadic eye movements. We find that a neural network model using a local associative synaptic learning rule, when exposed to visual scenes in conjunction with saccades, can account for a range of associated phenomena. In particular, our model demonstrates predictive and pre-saccadic remapping, responsiveness shifts around the time of saccades, and remapping from multiple directions. PMID:25717301

  1. Multiple Visual Field Representations in the Visual Wulst of a Laterally Eyed Bird, the Zebra Finch (Taeniopygia guttata)

    PubMed Central

    2016-01-01

    The visual wulst is the telencephalic target of the avian thalamofugal visual system. It contains several retinotopically organised representations of the contralateral visual field. We used optical imaging of intrinsic signals, electrophysiological recordings, and retrograde tracing with two fluorescent tracers to evaluate properties of these representations in the zebra finch, a songbird with laterally placed eyes. Our experiments revealed that there is some variability of the neuronal maps between individuals and also concerning the number of detectable maps. It was nonetheless possible to identify three different maps, a posterolateral, a posteromedial, and an anterior one, which were quite constant in their relation to each other. The posterolateral map was in contrast to the two others constantly visible in each successful experiment. The topography of the two other maps was mirrored against that map. Electrophysiological recordings in the anterior and the posterolateral map revealed that all units responded to flashes and to moving bars. Mean directional preferences as well as latencies were different between neurons of the two maps. Tracing experiments confirmed previous reports on the thalamo-wulst connections and showed that the anterior and the posterolateral map receive projections from separate clusters within the thalamic nuclei. Maps are connected to each other by wulst intrinsic projections. Our experiments confirm that the avian visual wulst contains several separate retinotopic maps with both different physiological properties and different thalamo-wulst afferents. This confirms that the functional organization of the visual wulst is very similar to its mammalian equivalent, the visual cortex. PMID:27139912

  2. Multiple Visual Field Representations in the Visual Wulst of a Laterally Eyed Bird, the Zebra Finch (Taeniopygia guttata).

    PubMed

    Bischof, Hans-Joachim; Eckmeier, Dennis; Keary, Nina; Löwel, Siegrid; Mayer, Uwe; Michael, Neethu

    2016-01-01

    The visual wulst is the telencephalic target of the avian thalamofugal visual system. It contains several retinotopically organised representations of the contralateral visual field. We used optical imaging of intrinsic signals, electrophysiological recordings, and retrograde tracing with two fluorescent tracers to evaluate properties of these representations in the zebra finch, a songbird with laterally placed eyes. Our experiments revealed that there is some variability of the neuronal maps between individuals and also concerning the number of detectable maps. It was nonetheless possible to identify three different maps, a posterolateral, a posteromedial, and an anterior one, which were quite constant in their relation to each other. The posterolateral map was in contrast to the two others constantly visible in each successful experiment. The topography of the two other maps was mirrored against that map. Electrophysiological recordings in the anterior and the posterolateral map revealed that all units responded to flashes and to moving bars. Mean directional preferences as well as latencies were different between neurons of the two maps. Tracing experiments confirmed previous reports on the thalamo-wulst connections and showed that the anterior and the posterolateral map receive projections from separate clusters within the thalamic nuclei. Maps are connected to each other by wulst intrinsic projections. Our experiments confirm that the avian visual wulst contains several separate retinotopic maps with both different physiological properties and different thalamo-wulst afferents. This confirms that the functional organization of the visual wulst is very similar to its mammalian equivalent, the visual cortex. PMID:27139912

  3. Habituation to novel visual vestibular environments with special reference to space flight

    NASA Technical Reports Server (NTRS)

    Young, L. R.; Kenyon, R. V.; Oman, C. M.

    1981-01-01

    The etiology of space motion sickness and the underlying physiological mechanisms associated with spatial orientation in a space environment were investigated. Human psychophysical experiments were used as the basis for the research concerning the interaction of visual and vestibular cues in the development of motion sickness. Particular emphasis is placed on the conflict theory in terms of explaining these interactions. Research on the plasticity of the vestibulo-ocular reflex is discussed.

  4. GCR Simulator Reference Field and a Spectral Approach for Laboratory Simulation

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Blattnig, Steve R.; Norbury, John W.; Rusek, Adam; La Tessa, Chiara; Walker, Steven A.

    2015-01-01

    The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, an approach for selecting beams at NSRL to simulate the designated reference field is presented. Drawbacks of the proposed methodology are discussed and weighed against alternative simulation strategies. The neutron component and track structure characteristics of the simulated field are discussed in this context.

  5. 6220 institutionalised people with intellectual disability referred for visual assessment between 1993 and 2003: overview and trends

    PubMed Central

    van Isterdael, C E D; Stilma, J S; Bezemer, P D; Tijmes, N T

    2006-01-01

    Aims To summarise the results of visual performance tests and other data of institutionalised people with intellectual disability referred to a visual advisory centre (VAC) between 1993 and 2003, and to determine trends in these data. Methods A retrospective medical record review was undertaken of 6220 consecutive people examined ophthalmologically according to a standard protocol by one VAC that specialised in visual assessment and treatment of people with intellectual disability, between 1993 and 2003. χ2 test for linear trend was used and linear regression coefficients were calculated. Results The proportion of people aged ⩾50 years increased from 19.3% to 34.2% between 1995 and 2003 (p<0.001); the combined figure of severe or profound intellectual disability decreased from 80.0% to 52.6% (p<0.001); the proportion of mobile people increased from 52.1% to 98.0% (p<0.001); the combined proportion of people with visual impairment or blindness decreased from 70.9% to 22.9% (p<0.001), and that of people with visual disorders decreased from 89.6% to 75.3% (p<0.001). Causes of intellectual disability were identified in 58.4% people; 20.8% had Down's syndrome. Conclusion Many ocular diagnoses were found, indicating the need for ophthalmological monitoring. Specialised centres are helpful, because assessment and treatment of people with intellectual disability is complicated and time consuming. Protocols for efficient referral will have to be developed. A major task lies ahead to improve the treatment rates of refractive errors, cataract and strabismus, and to find specific causes of intellectual disability. PMID:16854828

  6. Spatial Visualization Abilities of Field Dependent/Independent Preservice Teachers

    ERIC Educational Resources Information Center

    Yazici, Ersen

    2014-01-01

    Introduction: Spatial skills have been a significant area of research in educational psychology for more years and it has two major dimensions as spatial visualization and spatial orientation. Mathematics educators acknowledge the influence of cognitive styles in the learning of mathematics. There are various recognized cognitive styles in the…

  7. Geometric optical investigation of the underwater visual field of aerial animals.

    PubMed

    Horváth, G; Varjú, D

    1990-11-01

    The underwater visual field distorted by refraction for aerial animals living near the water surface is investigated by means of geometric optics. The imaging of underwater objects by one and two aerial eyes is studied. The underwater binocular image field is determined for pairs of aerial eyes placed in horizontal and vertical planes. Some possible biooptical consequences of the visual detection of underwater prey and predator by aerial animals are discussed on the basis of the structure of their distorted visual field. PMID:2134486

  8. Research on habituation to novel visual-vestibular environments with particular reference to space flight

    NASA Technical Reports Server (NTRS)

    Young, L. R.

    1976-01-01

    Progress in the development of a cohesive theory of the underlying physiological mechanisms associated with spatial orientation in unusual environments is described. Results can be applied to providing means of preventing and/or minimizing the space motion sickness which has been observed during prolonged space missions. Three major areas were investigated: (1) the interaction of visual and vestibular cues in conflict in the human, (2) the plasticity of the vestibulo-ocular reflex in monkeys, and (3) end organ function in the ray with particular emphasis on the effect of ionic concentration.

  9. APPLICATION OF A "VITURAL FIELD REFERENCE DATABASE" TO ASSESS LAND-COVER MAP ACCURACIES

    EPA Science Inventory

    An accuracy assessment was performed for the Neuse River Basin, NC land-cover/use
    (LCLU) mapping results using a "Virtual Field Reference Database (VFRDB)". The VFRDB was developed using field measurement and digital imagery (camera) data collected at 1,409 sites over a perio...

  10. AN ASSESSMENT OF GROUND TRUTH VARIABILITY USING A "VIRTUAL FIELD REFERENCE DATABASE"

    EPA Science Inventory



    A "Virtual Field Reference Database (VFRDB)" was developed from field measurment data that included location and time, physical attributes, flora inventory, and digital imagery (camera) documentation foy 1,01I sites in the Neuse River basin, North Carolina. The sampling f...

  11. Effects of a Blacklight Visual Field on Eye-Contact Training of Spastic Cerebral Palsied Children.

    ERIC Educational Resources Information Center

    Poland, D. J.; Doebler, L, K.

    1980-01-01

    Four subjects, aged six to seven, identified as visually impaired, were given training in making eye contact with a stimulus under both white and black light visual field. All subjects performed better under the black light condition, even overcoming the expected practice effect when white light training followed black light training. (Author/SJL)

  12. Right Visual Field Advantage for Perceived Contrast: Correlation with an Auditory Bias and Handedness

    ERIC Educational Resources Information Center

    Railo, H.; Tallus, J.; Hamalainen, H.

    2011-01-01

    Studies have suggested that supramodal attentional resources are biased rightward due to asymmetric spatial fields of the two hemispheres. This bias has been observed especially in right-handed subjects. We presented left and right-handed subjects with brief uniform grey visual stimuli in either the left or right visual hemifield. Consistent with…

  13. Masked Priming Is Abstract in the Left and Right Visual Fields

    ERIC Educational Resources Information Center

    Bowers, Jeffrey S.; Turner, Emma L.

    2005-01-01

    Two experiments assessed masked priming for words presented to the left and right visual fields in a lexical decision task. In both Experiments, the same magnitude and pattern of priming was obtained for visually similar ("kiss"-"KISS") and dissimilar ("read"-"READ") prime-target pairs. These findings provide no support for the hypothesis that…

  14. Pocket Monster incident and low luminance visual stimuli: special reference to deep red flicker stimulation.

    PubMed

    Takahashi, T; Tsukahara, Y

    1998-12-01

    On the evening of 16 December 1997 approximately 700 people around the nation (mostly children) were rushed to hospitals and treated for seizure symptoms. The youngsters had been watching the vastly popular TV animated cartoon series Pocket Monsters (Pokemon). We designated those individuals as a main group, who presumably had simultaneous occurrence of visually induced seizures. Follow-up studies revealed that 5-10.4% of Pokemon viewers had various minor symptoms not requiring hospital treatment. We designated those as a subgroup. Due to an official report regarding the problematic TV scene as a low luminance, 12 Hz alternating red/blue stimulus, we attempted an accounting of the Pokemon incident, with regard to the main group in particular, on the basis of electroencephalographic activation by use of low luminance 15 Hz deep red flicker stimulation. In order to explain the entire Pokemon incident, including symptoms experienced by individuals of the subgroup, we considered the possibility that some healthy youngsters may have latent photosensitivity and we thought that such a sensitivity might be disclosed by use of low luminance deep red flicker stimulation which is more provocative of photoparoxysmal response than ordinary high luminance stroboscopic intermittent photic stimulation. For prevention of visually induced seizures by TV viewing, we stress that care should be taken to test not only red flicker but also flickering geometric pattern stimuli. PMID:9893306

  15. Visual attention is not enough: Individual differences in statistical word-referent learning in infants.

    PubMed

    Smith, Linda B; Yu, Chen

    2013-01-01

    Recent evidence shows that infants can learn words and referents by aggregating ambiguous information across situations to discern the underlying word-referent mappings. Here, we use an individual difference approach to understand the role of different kinds of attentional processes in this learning: 12-and 14-month-old infants participated in a cross-situational word-referent learning task in which the learning trials were ordered to create local novelty effects, effects that should not alter the statistical evidence for the underlying correspondences. The main dependent measures were derived from frame-by-frame analyses of eye gaze direction. The fine- grained dynamics of looking behavior implicates different attentional processes that may compete with or support statistical learning. The discussion considers the role of attention in binding heard words to seen objects, individual differences in attention and vocabulary development, and the relation between macro-level theories of word learning and the micro-level dynamic processes that underlie learning. PMID:24403867

  16. Neural bandwidth of veridical perception across the visual field.

    PubMed

    Wilkinson, Michael O; Anderson, Roger S; Bradley, Arthur; Thibos, Larry N

    2016-01-01

    Neural undersampling of the retinal image limits the range of spatial frequencies that can be represented veridically by the array of retinal ganglion cells conveying visual information from eye to brain. Our goal was to demarcate the neural bandwidth and local anisotropy of veridical perception, unencumbered by optical imperfections of the eye, and to test competing hypotheses that might account for the results. Using monochromatic interference fringes to stimulate the retina with high-contrast sinusoidal gratings, we measured sampling-limited visual resolution along eight meridians from 0° to 50° of eccentricity. The resulting isoacuity contour maps revealed all of the expected features of the human array of retinal ganglion cells. Contours in the radial fringe maps are elongated horizontally, revealing the functional equivalent of the anatomical visual streak, and are extended into nasal retina and superior retina, indicating higher resolution along those meridians. Contours are larger in diameter for radial gratings compared to tangential or oblique gratings, indicating local anisotropy with highest bandwidth for radially oriented gratings. Comparison of these results to anatomical predictions indicates acuity is proportional to the sampling density of retinal ganglion cells everywhere in the retina. These results support the long-standing hypothesis that "pixel density" of the discrete neural image carried by the human optic nerve limits the spatial bandwidth of veridical perception at all retinal locations. PMID:26824638

  17. Visual projections routed to the auditory pathway in ferrets: receptive fields of visual neurons in primary auditory cortex.

    PubMed

    Roe, A W; Pallas, S L; Kwon, Y H; Sur, M

    1992-09-01

    How does cortex that normally processes inputs from one sensory modality respond when provided with input from a different modality? We have addressed such a question with an experimental preparation in which retinal input is routed to the auditory pathway in ferrets. Following neonatal surgical manipulations, a specific population of retinal ganglion cells is induced to innervate the auditory thalamus and provides visual input to cells in auditory cortex (Sur et al., 1988). We have now examined in detail the visual response properties of single cells in primary auditory cortex (A1) of these rewired animals and compared the responses to those in primary visual cortex (V1) of normal animals. Cells in A1 of rewired animals differed from cells in normal V1: they exhibited larger receptive field sizes and poorer visual responsivity, and responded with longer latencies to electrical stimulation of their inputs. However, striking similarities were also found. Like cells in normal V1, A1 cells in rewired animals exhibited orientation and direction selectivity and had simple and complex receptive field organizations. Furthermore, the degree of orientation and directional selectivity as well as the proportions of simple, complex, and nonoriented cells found in A1 and V1 were very similar. These results have significant implications for possible commonalities in intracortical processing circuits between sensory cortices, and for the role of inputs in specifying intracortical circuitry. PMID:1527604

  18. The 24-2 Visual Field Test Misses Central Macular Damage Confirmed by the 10-2 Visual Field Test and Optical Coherence Tomography

    PubMed Central

    Grillo, Lola M.; Wang, Diane L.; Ramachandran, Rithambara; Ehrlich, Alyssa C.; De Moraes, Carlos Gustavo; Ritch, Robert; Hood, Donald C.

    2016-01-01

    Purpose To determine the extent to which the 24-2 visual field (VF) misses macular damage confirmed with both 10-2 VF and optical coherence tomography (OCT) tests and to evaluate the patterns of damage missed. Methods One hundred forty-one eyes of 141 glaucoma patients or suspects underwent 24-2 VF (mean deviation [MD] better than −6 dB), 10-2 VF, and OCT testing. Retinal nerve fiber layer (RNFL) and retinal ganglion cell plus inner plexiform (RGC+) probability plots were combined with 10-2 VF probability plots. Eyes were classified as “abnormal macula” if abnormal regions on both the 10-2 VF and OCT plots agreed. The number of abnormal eyes missed (i.e., false negatives) was determined for the following 24-2 VF metrics: MD; pattern standard deviation (PSD); glaucoma hemifield test (GHT); cluster criteria (CC); and abnormal points within ± 10°. Eyes that were missed on one or more of the 24-2 metrics were classified by damage type based upon circumpapillary RNFL thickness plots. Results Fifty-nine (41.8%) eyes were classified as “abnormal macula,” and comprised the reference standard. Of the 59, 31 (52.5%) were missed by one or more of the 24-2 metrics. The individual 24-2 metrics missed between 7 (CC) and 20 (MD) eyes. The eyes missed had widespread macular damage, as well as both shallow and deep local defects. Conclusions Eyes with macular glaucomatous damage may be classified as normal based on the 24-2 VF alone. Translational Relevance To detect macular damage with perimetry, the 10-2 VF test (or a modified 24-2 VF test) is essential. PMID:27134774

  19. Comprehensive visual field test & diagnosis system in support of astronaut health and performance

    NASA Astrophysics Data System (ADS)

    Fink, Wolfgang; Clark, Jonathan B.; Reisman, Garrett E.; Tarbell, Mark A.

    Long duration spaceflight, permanent human presence on the Moon, and future human missions to Mars will require autonomous medical care to address both expected and unexpected risks. An integrated non-invasive visual field test & diagnosis system is presented for the identification, characterization, and automated classification of visual field defects caused by the spaceflight environment. This system will support the onboard medical provider and astronauts on space missions with an innovative, non-invasive, accurate, sensitive, and fast visual field test. It includes a database for examination data, and a software package for automated visual field analysis and diagnosis. The system will be used to detect and diagnose conditions affecting the visual field, while in space and on Earth, permitting the timely application of therapeutic countermeasures before astronaut health or performance are impaired. State-of-the-art perimetry devices are bulky, thereby precluding application in a spaceflight setting. In contrast, the visual field test & diagnosis system requires only a touchscreen-equipped computer or touchpad device, which may already be in use for other purposes (i.e., no additional payload), and custom software. The system has application in routine astronaut assessment (Clinical Status Exam), pre-, in-, and post-flight monitoring, and astronaut selection. It is deployable in operational space environments, such as aboard the International Space Station or during future missions to or permanent presence on the Moon and Mars.

  20. Development of Techniques for Visualization of Scalar and Vector Fields in the Immersive Environment

    NASA Technical Reports Server (NTRS)

    Bidasaria, Hari B.; Wilson, John W.; Nealy, John E.

    2005-01-01

    Visualization of scalar and vector fields in the immersive environment (CAVE - Cave Automated Virtual Environment) is important for its application to radiation shielding research at NASA Langley Research Center. A complete methodology and the underlying software for this purpose have been developed. The developed software has been put to use for the visualization of the earth s magnetic field, and in particular for the study of the South Atlantic Anomaly. The methodology has also been put to use for the visualization of geomagnetically trapped protons and electrons within Earth's magnetosphere.

  1. The subtlety of simple eyes: the tuning of visual fields to perceptual challenges in birds

    PubMed Central

    Martin, Graham R.

    2014-01-01

    Birds show interspecific variation both in the size of the fields of individual eyes and in the ways that these fields are brought together to produce the total visual field. Variation is found in the dimensions of all main parameters: binocular region, cyclopean field and blind areas. There is a phylogenetic signal with respect to maximum width of the binocular field in that passerine species have significantly broader field widths than non-passerines; broadest fields are found among crows (Corvidae). Among non-passerines, visual fields show considerable variation within families and even within some genera. It is argued that (i) the main drivers of differences in visual fields are associated with perceptual challenges that arise through different modes of foraging, and (ii) the primary function of binocularity in birds lies in the control of bill position rather than in the control of locomotion. The informational function of binocular vision does not lie in binocularity per se (two eyes receiving slightly different information simultaneously about the same objects from which higher-order depth information is extracted), but in the contralateral projection of the visual field of each eye. Contralateral projection ensures that each eye receives information from a symmetrically expanding optic flow-field from which direction of travel and time to contact targets can be extracted, particularly with respect to the control of bill position. PMID:24395967

  2. Reference field specification and preliminary beam selection strategy for accelerator-based GCR simulation

    NASA Astrophysics Data System (ADS)

    Slaba, Tony C.; Blattnig, Steve R.; Norbury, John W.; Rusek, Adam; La Tessa, Chiara

    2016-02-01

    The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities and possible biological considerations. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, a preliminary approach for selecting beams at NSRL to simulate the designated reference field is presented. This approach is not a final design for the GCR simulator, but rather a single step within a broader design strategy. It is shown that the beam selection methodology is tied directly to the reference environment, allows facility constraints to be incorporated, and may be adjusted to account for additional constraints imposed by biological or animal care considerations. The major biology questions are not addressed herein but are discussed in a companion paper published in the present issue of this journal. Drawbacks of the proposed methodology are discussed

  3. Reference field specification and preliminary beam selection strategy for accelerator-based GCR simulation.

    PubMed

    Slaba, Tony C; Blattnig, Steve R; Norbury, John W; Rusek, Adam; La Tessa, Chiara

    2016-02-01

    The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities and possible biological considerations. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, a preliminary approach for selecting beams at NSRL to simulate the designated reference field is presented. This approach is not a final design for the GCR simulator, but rather a single step within a broader design strategy. It is shown that the beam selection methodology is tied directly to the reference environment, allows facility constraints to be incorporated, and may be adjusted to account for additional constraints imposed by biological or animal care considerations. The major biology questions are not addressed herein but are discussed in a companion paper published in the present issue of this journal. Drawbacks of the proposed methodology are discussed

  4. SU-E-T-471: Small Field Jaw/MLC Reference Data

    SciTech Connect

    Kerns, J; Alvarez, P; Followill, D; Lowenstein, J; Molineu, A; Summers, P; Kry, S

    2014-06-01

    Purpose: In recent years the need for small field data of MLCs has increased due to the use of intensity-modulated radiation (IMRT), but moreover the use of stereotactic body radiation (SBRT) has increased, which uses not simply small field sizes, but small jaw and field sizes together. Having reference data for these small fields that is reliable would be invaluable to the physics community. Our study has gathered these values and the data distributions from the Radiological Physics Center's (RPC) site visits between 1990 and the present. Methods: For all measurements, the RPC used a 25 × 25 × 25cm water phantom placed at 100cm SSD. All measurements were made with an Exradin A16 cylindrical ion chamber at an effective depth of 10 cm. A total of 42 Varian machine measurements were used to compose the data for a 6 MV beam and 5 TrueBeam 6 MV flattening filter free (FFF) beams were used for FFF data. Results: Jaw/MLC fields were measured for both 6 MV and 6 MF FFF beams with the jaws and MLCs both at the following field sizes: 6×6, 4×4, 3×3, and 2×2cm. Measurements were normalized to the 10×10 field readings (defined by the jaws and MLC). Spread in the data was minimal and demonstrates a high level of accuracy of acquired data. Conclusion: Small field Jaw/MLC reference data for Varian 6MV and 6 MV FFF beams has been analyzed and presented here, composed of the aggregation of numerous RPC site visits. Obtaining reliable small field data remains difficult, however the RPC has collected high fidelity small field Jaw/MLC data. The data are presented as a reference along with their distributions, in such a way that the physicist can act based upon their own desired agreement with the reference data.

  5. The effects of fixation and restricted visual field on vection-induced motion sickness

    NASA Technical Reports Server (NTRS)

    Stern, Robert M.; Hu, Senqi; Anderson, Richard B.; Leibowitz, Herschel W.; Koch, Kenneth L.

    1990-01-01

    Approximately 60 percent of healthy human subjects experience motion sickness when exposed to a rotating optokinetic drum. Here, the effects of certain visual factors on susceptibility to motion sickness were determined. Vection data (illusory self-motion), horizontal eye movement recordings, subjective motion sickness report, and a measure of gastric myoelectric activity were obtained from 45 subjects, who were randomly divided into the following three groups: a control group that observed the entire visual field with no fixation, a group that fixated on a central target, and a third group that had a visual field restricted to 15 deg. The experimental session was divided into three 12-min periods: baseline, drum rotation, and recovery. The results showed that fixation greatly reduced nystagmus and slightly reduced vection. The restricted visual field slightly reduced nystagmus and greatly reduced vection. Both of these manipulations significantly reduced symptoms of motion sickness and abnormal gastric myoelectric activity.

  6. Reversible Cerebral Vasoconstriction Syndrome Presenting With Visual Field Defects.

    PubMed

    Raven, Meisha L; Ringeisen, Alexander L; McAllister, Angela R; Knoch, Daniel W

    2016-06-01

    A 45-year-old woman with a history of depression and anxiety, treated with selective serotonin reuptake inhibitors (SSRIs), experienced acute, recurrent, and severe bifrontal headaches. Over time, she developed a left homonymous hemianopia and mental status changes. MRA revealed segmental vasoconstriction of cerebral arteries in multiple vascular distributions. She was treated with a calcium-channel blocker and magnesium, and there was resolution of her symptoms and cerebrovascular changes. Her clinical course and neuroimaging findings were consistent with reversible cerebral vasoconstriction syndrome. Although rare, this disorder frequently manifests with visual complaints. Although the prognosis is generally favorable, patients with this syndrome require prompt diagnosis and care directed to avoid complications including stroke, seizure, and subarachnoid hemorrhage. PMID:26807800

  7. Sharper, Stronger, Faster Upper Visual Field Representation in Primate Superior Colliculus.

    PubMed

    Hafed, Ziad M; Chen, Chih-Yang

    2016-07-11

    Visually guided behavior in three-dimensional environments entails handling immensely different sensory and motor conditions across retinotopic visual field locations: peri-personal ("near") space is predominantly viewed through the lower retinotopic visual field (LVF), whereas extra-personal ("far") space encompasses the upper visual field (UVF). Thus, when, say, driving a car, orienting toward the instrument cluster below eye level is different from scanning an upcoming intersection, even with similarly sized eye movements. However, an overwhelming assumption about visuomotor circuits for eye-movement exploration, like those in the primate superior colliculus (SC), is that they represent visual space in a purely symmetric fashion across the horizontal meridian. Motivated by ecological constraints on visual exploration of far space, containing small UVF retinal-image features, here we found a large, multi-faceted difference in the SC's representation of the UVF versus LVF. Receptive fields are smaller, more finely tuned to image spatial structure, and more sensitive to image contrast for neurons representing the UVF. Stronger UVF responses also occur faster. Analysis of putative synaptic activity revealed a particularly categorical change when the horizontal meridian is crossed, and our observations correctly predicted novel eye-movement effects. Despite its appearance as a continuous layered sheet of neural tissue, the SC contains functional discontinuities between UVF and LVF representations, paralleling a physical discontinuity present in cortical visual areas. Our results motivate the recasting of structure-function relationships in the visual system from an ecological perspective, and also exemplify strong coherence between brain-circuit organization for visually guided exploration and the nature of the three-dimensional environment in which we function. PMID:27291052

  8. Hawk Eyes I: Diurnal Raptors Differ in Visual Fields and Degree of Eye Movement

    PubMed Central

    O'Rourke, Colleen T.; Hall, Margaret I.; Pitlik, Todd; Fernández-Juricic, Esteban

    2010-01-01

    Background Different strategies to search and detect prey may place specific demands on sensory modalities. We studied visual field configuration, degree of eye movement, and orbit orientation in three diurnal raptors belonging to the Accipitridae and Falconidae families. Methodology/Principal Findings We used an ophthalmoscopic reflex technique and an integrated 3D digitizer system. We found inter-specific variation in visual field configuration and degree of eye movement, but not in orbit orientation. Red-tailed Hawks have relatively small binocular areas (∼33°) and wide blind areas (∼82°), but intermediate degree of eye movement (∼5°), which underscores the importance of lateral vision rather than binocular vision to scan for distant prey in open areas. Cooper's Hawks' have relatively wide binocular fields (∼36°), small blind areas (∼60°), and high degree of eye movement (∼8°), which may increase visual coverage and enhance prey detection in closed habitats. Additionally, we found that Cooper's Hawks can visually inspect the items held in the tip of the bill, which may facilitate food handling. American Kestrels have intermediate-sized binocular and lateral areas that may be used in prey detection at different distances through stereopsis and motion parallax; whereas the low degree eye movement (∼1°) may help stabilize the image when hovering above prey before an attack. Conclusions We conclude that: (a) there are between-species differences in visual field configuration in these diurnal raptors; (b) these differences are consistent with prey searching strategies and degree of visual obstruction in the environment (e.g., open and closed habitats); (c) variations in the degree of eye movement between species appear associated with foraging strategies; and (d) the size of the binocular and blind areas in hawks can vary substantially due to eye movements. Inter-specific variation in visual fields and eye movements can influence behavioral

  9. Bumblebees measure optic flow for position and speed control flexibly within the frontal visual field.

    PubMed

    Linander, Nellie; Dacke, Marie; Baird, Emily

    2015-04-01

    When flying through narrow spaces, insects control their position by balancing the magnitude of apparent image motion (optic flow) experienced in each eye and their speed by holding this value about a desired set point. Previously, it has been shown that when bumblebees encounter sudden changes in the proximity to nearby surfaces - as indicated by a change in the magnitude of optic flow on each side of the visual field - they adjust their flight speed well before the change, suggesting that they measure optic flow for speed control at low visual angles in the frontal visual field. Here, we investigated the effect that sudden changes in the magnitude of translational optic flow have on both position and speed control in bumblebees if these changes are asymmetrical; that is, if they occur only on one side of the visual field. Our results reveal that the visual region over which bumblebees respond to optic flow cues for flight control is not dictated by a set viewing angle. Instead, bumblebees appear to use the maximum magnitude of translational optic flow experienced in the frontal visual field. This strategy ensures that bumblebees use the translational optic flow generated by the nearest obstacles - that is, those with which they have the highest risk of colliding - to control flight. PMID:25657205

  10. Field visual perspective during autobiographical memory recall is less frequent among patients with schizophrenia.

    PubMed

    Potheegadoo, Jevita; Berna, Fabrice; Cuervo-Lombard, Christine; Danion, Jean-Marie

    2013-10-01

    There is growing interest in clinical research regarding the visual perspective adopted during memory retrieval, because it reflects individuals' self-attitude towards their memories of past personal events. Several autobiographical memory deficits, including low specificity of personal memories, have been identified in schizophrenia, but visual perspective during autobiographical memory retrieval has not yet been investigated in patients. The aim of this study was therefore to investigate the visual perspective with which patients visualize themselves when recalling autobiographical memories and to assess the specificity of their memories which is a major determinant of visual perspective. Thirty patients with schizophrenia and 30 matched controls recalled personal events from 4 life periods. After each recall, they were asked to report their visual perspective (Field or Observer) associated with the event. The specificity of their memories was assessed by independent raters. Our results showed that patients reported significantly fewer Field perspectives than comparison participants. Patients' memories, whether recalled with Field or Observer perspectives, were less specific and less detailed. Our results indicate that patients with schizophrenia adopt Field perspectives less frequently than comparison participants, and that this may contribute to a weakened sense of the individual of being an actor of his past events, and hence to a reduced sense of self. They suggest that this may be related to low specificity of memories and that all the important aspects involved in re-experiencing autobiographical events are impaired in patients with schizophrenia. PMID:23932447

  11. Researching Refugee and Forced Migration Studies: An Introduction to the Field and the Reference Literature.

    ERIC Educational Resources Information Center

    Mason, Elisa

    1999-01-01

    Describes the evolution of refugee and forced migration studies, identifies factors that render it a challenging field to research, and highlights a variety of Internet-based and other electronic resources that can be used to locate monographs, periodicals, grey literature, and current information. Provides a bibliography of reference materials in…

  12. Religious Studies: The Shaping of a Field and a Guide to Reference Resources.

    ERIC Educational Resources Information Center

    Lippy, Charles H.

    1992-01-01

    Discusses the development of religious studies as an academic discipline. Examines the work of leading thinkers in the field, including anthropologists Sir James Fraser and Edward Burnett Taylor, sociologist Max Weber, and psychologist Erik Erikson. Identifies some of the many reference works that deal with religious studies. (SG)

  13. Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, I.-Hsiu; Chu, Shi-Wei; Bresson, Francois; Tien, Ming-Chun; Shi, Jin-Wei; Sun, Chi-Kuang

    2003-08-01

    An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field distribution can be easily visualized with high spatial resolution of the order of 1 μm.

  14. Visualizing Special Relativity: The Field of An Electric Dipole Moving at Relativistic Speed

    ERIC Educational Resources Information Center

    Smith, Glenn S.

    2011-01-01

    The electromagnetic field is determined for a time-varying electric dipole moving with a constant velocity that is parallel to its moment. Graphics are used to visualize this field in the rest frame of the dipole and in the laboratory frame when the dipole is moving at relativistic speed. Various phenomena from special relativity are clearly…

  15. Evaluation of models proposed for the 1991 revision of the International Geomagnetic Reference Field

    USGS Publications Warehouse

    Peddie, N.W.

    1992-01-01

    The 1991 revision of the International Geomagnetic Reference Field (IGRF) comprises a definitive main-field model for 1985.0, a main-field model for 1990.0, and a forecast secular-variation model for the period 1990-1995. The five 1985.0 main-field models and five 1990.0 main-field models that were proposed have been evaluated by comparing them with one another, with magnetic observatory data, and with Project MAGNET aerial survey data. The comparisons indicate that the main-field models proposed by IZMIRAN, and the secular-variation model proposed jointly by the British Geological Survey and the US Naval Oceanographic Office, should be assigned relatively lower weight in the derivation of the new IGRF models. -Author

  16. Abnormal visual field maps in human cortex: a mini-review and a case report.

    PubMed

    Haak, Koen V; Langers, Dave R M; Renken, Remco; van Dijk, Pim; Borgstein, Johannes; Cornelissen, Frans W

    2014-07-01

    Human visual cortex contains maps of the visual field. Much research has been dedicated to answering whether and when these visual field maps change if critical components of the visual circuitry are damaged. Here, we first provide a focused mini-review of the functional magnetic resonance imaging (fMRI) studies that have evaluated the human cortical visual field maps in the face of retinal lesions, brain injury, and atypical retinocortical projections. We find that there is a fair body of research that has found abnormal fMRI activity, but also that this abnormal activity does not necessarily stem from cortical remapping. The abnormal fMRI activity can often be explained in terms of task effects and/or the uncovering of normally hidden system dynamics. We then present the case of a 16-year-old patient who lost the entire left cerebral hemisphere at age three for treatment of chronic focal encephalitis (Rasmussen syndrome) and intractable epilepsy. Using an fMRI retinotopic mapping procedure and population receptive field (pRF) modeling, we found that (1) despite the long period since the hemispherectomy, the retinotopic organization of early visual cortex remained unaffected by the removal of an entire cerebral hemisphere, and (2) the intact lateral occipital cortex contained an exceptionally large representation of the center of the visual field. The same method also indicates that the neuronal receptive fields in these lateral occipital brain regions are extraordinarily small. These features are clearly abnormal, but again they do not necessarily stem from cortical remapping. For example, the abnormal features can also be explained by the notion that the hemispherectomy took place during a critical period in the development of the lateral occipital cortex and therefore arrested its normal development. Thus, caution should be exercised when interpreting abnormal fMRI activity as a marker of cortical remapping; there are often other explanations. PMID:23347557

  17. Characteristics of Eye-Position Gain Field Populations Determine Geometry of Visual Space

    PubMed Central

    Lehky, Sidney R.; Sereno, Margaret E.; Sereno, Anne B.

    2016-01-01

    We have previously demonstrated differences in eye-position spatial maps for anterior inferotemporal cortex (AIT) in the ventral stream and lateral intraparietal cortex (LIP) in the dorsal stream, based on population decoding of gaze angle modulations of neural visual responses (i.e., eye-position gain fields). Here we explore the basis of such spatial encoding differences through modeling of gain field characteristics. We created a population of model neurons, each having a different eye-position gain field. This population was used to reconstruct eye-position visual space using multidimensional scaling. As gain field shapes have never been well-established experimentally, we examined different functions, including planar, sigmoidal, elliptical, hyperbolic, and mixtures of those functions. All functions successfully recovered positions, indicating weak constraints on allowable gain field shapes. We then used a genetic algorithm to modify the characteristics of model gain field populations until the recovered spatial maps closely matched those derived from monkey neurophysiological data in AIT and LIP. The primary differences found between model AIT and LIP gain fields were that AIT gain fields were more foveally dominated. That is, gain fields in AIT operated on smaller spatial scales and smaller dispersions than in LIP. Thus, we show that the geometry of eye-position visual space depends on the population characteristics of gain fields, and that differences in gain field characteristics for different cortical areas may underlie differences in the representation of space. PMID:26834587

  18. [Does music influence visual perception in campimetric measurements of the visual field?].

    PubMed

    Gall, Carolin; Geier, Jens-Stefan; Sabel, Bernhard A; Kasten, Erich

    2009-01-01

    21 subjects (mean age 28,4 +/- 10,9, M +/- SD) without any damage of the visual system were examined with computer-based campimetric tests of near threshold stimulus detection whereby an artificial tunnel vision was induced. Campimetry was performed in four trials in randomized order using a within-subjects-design: 1. classical music, 2. Techno music, 3. music for relaxation and 4. no music. Results were slightly better in all music conditions. Performance was best when subjects were listening to Techno music. The average increase of correctly recognized stimuli and fixation controls amounted to 3 %. To check the stability of the effects 9 subjects were tested three times. A moderating influence of personality traits and habits of listening to music was tested but could not be found. We conclude that music has at least no negative influence on performance in the campimetric measurement. Reasons for the positive effects of music can be seen in a general increase of vigilance and a modulation of perceptual thresholds. PMID:18240114

  19. Visual field bias in hearing and deaf adults during judgments of facial expression and identity.

    PubMed

    Letourneau, Susan M; Mitchell, Teresa V

    2013-01-01

    The dominance of the right hemisphere during face perception is associated with more accurate judgments of faces presented in the left rather than the right visual field (RVF). Previous research suggests that the left visual field (LVF) bias typically observed during face perception tasks is reduced in deaf adults who use sign language, for whom facial expressions convey important linguistic information. The current study examined whether visual field biases were altered in deaf adults whenever they viewed expressive faces, or only when attention was explicitly directed to expression. Twelve hearing adults and 12 deaf signers were trained to recognize a set of novel faces posing various emotional expressions. They then judged the familiarity or emotion of faces presented in the left or RVF, or both visual fields simultaneously. The same familiar and unfamiliar faces posing neutral and happy expressions were presented in the two tasks. Both groups were most accurate when faces were presented in both visual fields. Across tasks, the hearing group demonstrated a bias toward the LVF. In contrast, the deaf group showed a bias toward the LVF during identity judgments that shifted marginally toward the RVF during emotion judgments. Two secondary conditions tested whether these effects generalized to angry faces and famous faces and similar effects were observed. These results suggest that attention to facial expression, not merely the presence of emotional expression, reduces a typical LVF bias for face processing in deaf signers. PMID:23761774

  20. Resilience to the contralateral visual field bias as a window into object representations.

    PubMed

    Garcea, Frank E; Kristensen, Stephanie; Almeida, Jorge; Mahon, Bradford Z

    2016-08-01

    Viewing images of manipulable objects elicits differential blood oxygen level-dependent (BOLD) contrast across parietal and dorsal occipital areas of the human brain that support object-directed reaching, grasping, and complex object manipulation. However, it is unknown which object-selective regions of parietal cortex receive their principal inputs from the ventral object-processing pathway and which receive their inputs from the dorsal object-processing pathway. Parietal areas that receive their inputs from the ventral visual pathway, rather than from the dorsal stream, will have inputs that are already filtered through object categorization and identification processes. This predicts that parietal regions that receive inputs from the ventral visual pathway should exhibit object-selective responses that are resilient to contralateral visual field biases. To test this hypothesis, adult participants viewed images of tools and animals that were presented to the left or right visual fields during functional magnetic resonance imaging (fMRI). We found that the left inferior parietal lobule showed robust tool preferences independently of the visual field in which tool stimuli were presented. In contrast, a region in posterior parietal/dorsal occipital cortex in the right hemisphere exhibited an interaction between visual field and category: tool-preferences were strongest contralateral to the stimulus. These findings suggest that action knowledge accessed in the left inferior parietal lobule operates over inputs that are abstracted from the visual input and is contingent on analysis by the ventral visual pathway, consistent with its putative role in supporting object manipulation knowledge. PMID:27160998

  1. Eye torsion and the apparent horizon under head tilt and visual field rotation

    NASA Technical Reports Server (NTRS)

    Merker, B. H.; Held, R.

    1981-01-01

    Two different experimental manipulations, namely head tilt and the viewing of a visual display rotating around the line of sight, induce torsional displacements of the eyes and a tilting of the apparent horizon. The present study examines the routes by which visual (field rotation) and otolith-proprioceptive (head tilt) sources of afference influence horizon judgments. In particular, the relationship between torsional eye movements and horizon estimates is addressed. The results indicate that visual and otolith-proprioceptive information sum directly in their influence on eye torsion, but interact more complexly in horizon estimates, indicating a dissociation of their central determinants.

  2. Problems Confronting Visual Culture

    ERIC Educational Resources Information Center

    Efland, Arthur D.

    2005-01-01

    A new movement has appeared recommending, in part, that the field of art education should lessen its traditional ties to drawing, painting, and the study of masterpieces to become the study of visual culture. Visual cultural study refers to an all-encompassing category of cultural practice that includes the fine arts but also deals with the study…

  3. Visual Field Loss Morphology in High- and Normal-Tension Glaucoma

    PubMed Central

    Iester, Michele; De Feo, Fabio; Douglas, Gordon R.

    2012-01-01

    Purpose. To determine whether the patterns of visual field damage between high-tension glaucoma (HTG) and normal-tension glaucoma (NTG) are equivalent. Methods. In this retrospective cross-sectional study, fifty-one NTG and 57 HTG patients were recruited. For each recruited patient only the left eye was chosen. Glaucomatous patients had abnormal visual fields and/or glaucomatous changes at the optic nerve head. They were classified as HTG or NTG on the basis of intraocular pressure (IOP) measurements. Patients' visual fields were analyzed by using Humphrey Field Analyzer (HFA), program 30-2, full threshold. The visual field sensitivity values and the pattern deviation map values of the 72 tested points were considered. Then a pointwise analysis and an area analysis, based on the Glaucoma Hemifield test criteria, were performed, and a comparison between the two subgroups was made by Student's t test. Results. Between NTG and HTG, no significant difference was found pointwise for almost all the visual field points, except for two locations. One was under the blind spot, and the other was in the inferior hemifield around the twenty-degree position. When area analysis was considered, three areas showed a significantly different sensitivity between HTG and NTG. Conclusions. These data suggested that there was no relevant difference in the pointwise analysis between NTG and HTG; however, when visual field areas were compared, no difference in paracentral areas was found between NTG and HTG, but superior nasal step and inferior and superior scotomata showed to be deeper in HTG than in NTG. PMID:22496961

  4. Driving simulation in the clinic: testing visual exploratory behavior in daily life activities in patients with visual field defects.

    PubMed

    Hamel, Johanna; Kraft, Antje; Ohl, Sven; De Beukelaer, Sophie; Audebert, Heinrich J; Brandt, Stephan A

    2012-01-01

    Patients suffering from homonymous hemianopia after infarction of the posterior cerebral artery (PCA) report different degrees of constraint in daily life, despite similar visual deficits. We assume this could be due to variable development of compensatory strategies such as altered visual scanning behavior. Scanning compensatory therapy (SCT) is studied as part of the visual training after infarction next to vision restoration therapy. SCT consists of learning to make larger eye movements into the blind field enlarging the visual field of search, which has been proven to be the most useful strategy(1), not only in natural search tasks but also in mastering daily life activities(2). Nevertheless, in clinical routine it is difficult to identify individual levels and training effects of compensatory behavior, since it requires measurement of eye movements in a head unrestrained condition. Studies demonstrated that unrestrained head movements alter the visual exploratory behavior compared to a head-restrained laboratory condition(3). Martin et al.(4) and Hayhoe et al.(5) showed that behavior demonstrated in a laboratory setting cannot be assigned easily to a natural condition. Hence, our goal was to develop a study set-up which uncovers different compensatory oculomotor strategies quickly in a realistic testing situation: Patients are tested in the clinical environment in a driving simulator. SILAB software (Wuerzburg Institute for Traffic Sciences GmbH (WIVW)) was used to program driving scenarios of varying complexity and recording the driver's performance. The software was combined with a head mounted infrared video pupil tracker, recording head- and eye-movements (EyeSeeCam, University of Munich Hospital, Clinical Neurosciences). The positioning of the patient in the driving simulator and the positioning, adjustment and calibration of the camera is demonstrated. Typical performances of a patient with and without compensatory strategy and a healthy control are

  5. Driving Simulation in the Clinic: Testing Visual Exploratory Behavior in Daily Life Activities in Patients with Visual Field Defects

    PubMed Central

    Hamel, Johanna; Kraft, Antje; Ohl, Sven; De Beukelaer, Sophie; Audebert, Heinrich J.; Brandt, Stephan A.

    2012-01-01

    Patients suffering from homonymous hemianopia after infarction of the posterior cerebral artery (PCA) report different degrees of constraint in daily life, despite similar visual deficits. We assume this could be due to variable development of compensatory strategies such as altered visual scanning behavior. Scanning compensatory therapy (SCT) is studied as part of the visual training after infarction next to vision restoration therapy. SCT consists of learning to make larger eye movements into the blind field enlarging the visual field of search, which has been proven to be the most useful strategy1, not only in natural search tasks but also in mastering daily life activities2. Nevertheless, in clinical routine it is difficult to identify individual levels and training effects of compensatory behavior, since it requires measurement of eye movements in a head unrestrained condition. Studies demonstrated that unrestrained head movements alter the visual exploratory behavior compared to a head-restrained laboratory condition3. Martin et al.4 and Hayhoe et al.5 showed that behavior demonstrated in a laboratory setting cannot be assigned easily to a natural condition. Hence, our goal was to develop a study set-up which uncovers different compensatory oculomotor strategies quickly in a realistic testing situation: Patients are tested in the clinical environment in a driving simulator. SILAB software (Wuerzburg Institute for Traffic Sciences GmbH (WIVW)) was used to program driving scenarios of varying complexity and recording the driver's performance. The software was combined with a head mounted infrared video pupil tracker, recording head- and eye-movements (EyeSeeCam, University of Munich Hospital, Clinical Neurosciences). The positioning of the patient in the driving simulator and the positioning, adjustment and calibration of the camera is demonstrated. Typical performances of a patient with and without compensatory strategy and a healthy control are illustrated in

  6. [Concentric changes in the visual field associated with GABA-mimetic antiepileptic agents].

    PubMed

    Nordmann, J P; Baulac, M; Van Egroo, C

    1999-05-01

    Bilateral visual field constriction has been recently reported in patients treated with vigabatrin. It has been considered that vigabatrin, a GABA agonist antiepileptic drug, was specifically responsible for this visual field defect. We present four observations sharing the same characteristics of chronic tunnel vision. Three patients had had vigabatrin but the fourth one received other antiepileptic drugs, progabide, an agonist of post-synaptic GABA receptors, and phenobarbital which interferes with GABA-A receptors. It is thus possible to hypothesize a retinal toxicity triggered by chronically increased GABA transmission. If this is confirmed, an accurate incidence of symptomatic and asymptomatic visual field constriction with GABA-mimetic drugs should be established, as well as the patients' profiles which are more at risk. Patients currently under this type of treatment should be checked by both manual and automatic perimetry every six months to one year. PMID:10365327

  7. Optoelectronic aid for patients with severely restricted visual fields in daylight conditions

    NASA Astrophysics Data System (ADS)

    Peláez-Coca, María Dolores; Sobrado-Calvo, Paloma; Vargas-Martín, Fernando

    2011-11-01

    In this study we evaluated the immediate effectiveness of an optoelectronic visual field expander in a sample of subjects with retinitis pigmentosa suffering from a severe peripheral visual field restriction. The aid uses the augmented view concept and provides subjects with visual information from outside their visual field. The tests were carried out in daylight conditions. The optoelectronic aid comprises a FPGA (real-time video processor), a wide-angle mini camera and a transparent see-through head-mounted display. This optoelectronic aid is called SERBA (Sistema Electro-óptico Reconfigurable de Ayuda para Baja Visión). We previously showed that, without compromising residual vision, the SERBA system provides information about objects within an area about three times greater on average than the remaining visual field of the subjects [1]. In this paper we address the effects of the device on mobility under daylight conditions with and without SERBA. The participants were six subjects with retinitis pigmentosa. In this mobility test, better results were obtained when subjects were wearing the SERBA system; specifically, both the number of contacts with low-level obstacles and mobility errors decreased significantly. A longer training period with the device might improve its usefulness.

  8. Experimental investigation of the visual field dependency in the erect and supine positions

    NASA Technical Reports Server (NTRS)

    Lichtenstein, J. H.; Saucer, R. T.

    1972-01-01

    The increasing utilization of simulators in many fields, in addition to aeronautics and space, requires the efficient use of these devices. It seemed that personnel highly influenced by the visual scene would make desirable subjects, particularly for those simulators without sufficient motion cues. In order to evaluate this concept, some measure of the degree of influence of the visual field on the subject in necessary. As part of this undertaking, 37 male and female subjects, including eight test pilots, were tested for their visual field dependency or independency. A version of Witkin's rod and frame apparatus was used for the tests. The results showed that nearly all the test subjects exhibited some degree of field dependency, the degree varying from very high field dependency to nearly zero field dependency in a normal distribution. The results for the test pilots were scattered throughout a range similar to the results for the bulk of male subjects. The few female subjects exhibited a higher field dependency than the male subjects. The male subjects exhibited a greater field dependency in the supine position than in the erect position, whereas the field dependency of the female subjects changed only slightly.

  9. A technique for simulating visual field losses in virtual environments to study human navigation.

    PubMed

    Fortenbaugh, Francesca C; Hicks, John C; Hao, Lei; Turano, Kathleen A

    2007-08-01

    The following paper describes a new technique for simulating peripheral field losses in virtual environments to study the roles of the central and peripheral visual fields during navigation. Based on Geisler and Perry's (2002) gaze-contingent multiresolution display concept, the technique extends their methodology to work with three-dimensional images that are both transformed and rendered in real time by a computer graphics system. In order to assess the usefulness of this method for studying visual field losses, an experiment was run in which seven participants were required to walk to a target tree in a virtual forest as quickly and efficiently as possible while artificial head and eye-based delays were systematically introduced. Bilinear fits were applied to the mean trial times in order to assess at what delay lengths breaks in performance could be observed. Results suggest that breaks occur beyond the current delays inherent in the system. Increases in trial times across all delays tested were also observed when simulated peripheral field losses were applied compared to full FOV conditions. Possible applications and limitations of the system are discussed. The source code needed to program visual field losses can be found at lions.med.jhu.edu/archive/turanolab/Simulated_Visual_Field_Loss_Code.html. PMID:17958167

  10. A Reference Field for GCR Simulation and an LET-Based Implementation at NSRL

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Blattnig, Steve R.; Walker, Steven A.; Norbury, John W.

    2015-01-01

    Exposure to galactic cosmic rays (GCR) on long duration deep space missions presents a serious health risk to astronauts, with large uncertainties connected to the biological response. In order to reduce the uncertainties and gain understanding about the basic mechanisms through which space radiation initiates cancer and other endpoints, radiobiology experiments are performed. Some of the accelerator facilities supporting such experiments have matured to a point where simulating the broad range of particles and energies characteristic of the GCR environment in a single experiment is feasible from a technology, usage, and cost perspective. In this work, several aspects of simulating the GCR environment in the laboratory are discussed. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at the NASA Space Radiation Laboratory (NSRL) limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is within physical uncertainties, allowing a single reference field for deep space missions to be defined. Third, an approach for simulating the reference field at NSRL is presented. The approach allows for the linear energy transfer (LET) spectrum of the reference field to be approximately represented with discrete ion and energy beams and implicitly maintains a reasonably accurate charge spectrum (or, average quality factor). Drawbacks of the proposed methodology are discussed and weighed against alternative simulation strategies. The neutron component and track structure characteristics of the proposed strategy are discussed in this context.

  11. Arteriovenous Passage Times and Visual Field Progression in Normal Tension Glaucoma

    PubMed Central

    Koch, Eva Charlotte; Arend, Kay Oliver; Bienert, Marion; Remky, Andreas

    2013-01-01

    Purpose. Fluorescein angiographic studies revealed prolonged arteriovenous passage (AVP) times and increased fluorescein filling defects in normal tension glaucoma (NTG) compared to healthy controls. The purpose of this study was to correlate baseline AVP and fluorescein filling defects with visual field progression in patients with NTG. Patients and Methods. Patients with a follow-up period of at least 3 years and at least 4 visual field examinations were included in this retrospective study. Fluorescein angiography was performed at baseline using a confocal scanning laser ophthalmoscope (SLO, Rodenstock Instr.); fluorescein filling defects and AVP were measured by digital image analysis and dye dilution curves (25 Hz). Visual field progression was evaluated using regression analysis of the MD (Humphrey-Zeiss, SITA-24-2, MD progression per year (dB/year)). 72 patients with NTG were included, 44 patients in study 1 (fluorescein filling defects) and 28 patients in study 2 (AVP). Results. In study 1 (mean follow-up 6.6 ± 1.9 years, 10 ± 5 visual field tests), MD progression per year (−0.51 ± 0.59 dB/year) was significantly correlated to the age (P = 0.04, r = -0.29) but not to fluorescein filling defects, IOP, or MD at baseline. In study 2 (mean follow-up 6.6 ± 2.2 years, 10 ± 5 visual field tests), MD progression per year (−0.45 ± 0.51 dB/year) was significantly correlated to AVP (P = 0.03, r = 0.39) but not to age, IOP, or MD at baseline. Conclusion. Longer AVP times at baseline are correlated to visual field progression in NTG. Impaired retinal blood flow seems to be an important factor for glaucoma progression. PMID:24282387

  12. Retinal Ganglion Cell Count Estimates Associated with Early Development of Visual Field Defects in Glaucoma

    PubMed Central

    Medeiros, Felipe A.; Lisboa, Renato; Weinreb, Robert N.; Liebmann, Jeffrey M.; Girkin, Christopher; Zangwill, Linda M.

    2013-01-01

    Purpose To estimate retinal ganglion cell (RGC) losses associated with the earliest development of visual field defects in glaucoma. Design Observational cohort study. Participants The study group included 53 eyes of 53 patients suspected of having glaucoma who were followed as part of the Diagnostic Innovations in Glaucoma (DIGS) study. These eyes had normal standard automated perimetry (SAP) visual fields at baseline and developed repeatable (3 consecutive) abnormal tests during a median follow-up of 6.7 years. An age-matched control group of 124 eyes of 124 healthy subjects recruited from the general population was included. Methods Estimates of RGC counts were obtained using a previously published model which combines estimates of RGC numbers from SAP sensitivity thresholds and retinal nerve fiber layer (RNFL) thickness measurements with spectral domain optical coherence tomography (SDOCT). For eyes converting to glaucoma, estimates of RGC counts were obtained at the time (within ± 3 months) of the first abnormal visual field, representing the time of earliest detection of visual field losses. Main Outcome Measures Estimates of RGC counts in eyes converting to glaucoma versus healthy eyes. Results The average RGC count estimate in the eyes with early visual field defects was 652057 ± 115829 cells, which was significantly lower than the average of 910584 ± 142412 cells found in healthy eyes (P<0.001). Compared to the average number of RGCs in the healthy group, glaucoma eyes had an average RGC loss of 28.4%, ranging from 6% to 57%, at the time of the earliest visual field defect on SAP. RGC counts performed significantly better than the SDOCT average RNFL thickness parameter in discriminating glaucomatous from healthy eyes with ROC curve areas of 0.95 ± 0.02 versus 0.88 ±0.03, respectively (P=0.001). Conclusion Glaucomatous eyes with the earliest detectable visual field loss on automated perimetry may already show substantial loss of retinal ganglion cells

  13. Risk factors for progression of visual field defects in medically treated patients with glaucoma.

    PubMed

    Richler, M; Werner, E B; Thomas, D

    1982-12-01

    A multivariate discriminant analysis of potential risk factors for the progression of visual field defects was performed in 70 patients with chronic open-angle or low-tension glaucoma. Male sex, low diastolic blood pressure and diabetes mellitus were found to be significant risk factors. When the patients with low-tension glaucoma were excluded, a high mean intraocular pressure was identified as a risk factor. It was concluded that there is no reliable way to predict future visual field loss in patients with glaucoma. PMID:7165838

  14. Response bias reveals enhanced attention to inferior visual field in signers of American Sign Language.

    PubMed

    Dye, Matthew W G; Seymour, Jenessa L; Hauser, Peter C

    2016-04-01

    Deafness results in cross-modal plasticity, whereby visual functions are altered as a consequence of a lack of hearing. Here, we present a reanalysis of data originally reported by Dye et al. (PLoS One 4(5):e5640, 2009) with the aim of testing additional hypotheses concerning the spatial redistribution of visual attention due to deafness and the use of a visuogestural language (American Sign Language). By looking at the spatial distribution of errors made by deaf and hearing participants performing a visuospatial selective attention task, we sought to determine whether there was evidence for (1) a shift in the hemispheric lateralization of visual selective function as a result of deafness, and (2) a shift toward attending to the inferior visual field in users of a signed language. While no evidence was found for or against a shift in lateralization of visual selective attention as a result of deafness, a shift in the allocation of attention from the superior toward the inferior visual field was inferred in native signers of American Sign Language, possibly reflecting an adaptation to the perceptual demands imposed by a visuogestural language. PMID:26708522

  15. Emotion separation is completed early and it depends on visual field presentation.

    PubMed

    Liu, Lichan; Ioannides, Andreas A

    2010-01-01

    It is now apparent that the visual system reacts to stimuli very fast, with many brain areas activated within 100 ms. It is, however, unclear how much detail is extracted about stimulus properties in the early stages of visual processing. Here, using magnetoencephalography we show that the visual system separates different facial expressions of emotion well within 100 ms after image onset, and that this separation is processed differently depending on where in the visual field the stimulus is presented. Seven right-handed males participated in a face affect recognition experiment in which they viewed happy, fearful and neutral faces. Blocks of images were shown either at the center or in one of the four quadrants of the visual field. For centrally presented faces, the emotions were separated fast, first in the right superior temporal sulcus (STS; 35-48 ms), followed by the right amygdala (57-64 ms) and medial pre-frontal cortex (83-96 ms). For faces presented in the periphery, the emotions were separated first in the ipsilateral amygdala and contralateral STS. We conclude that amygdala and STS likely play a different role in early visual processing, recruiting distinct neural networks for action: the amygdala alerts sub-cortical centers for appropriate autonomic system response for fight or flight decisions, while the STS facilitates more cognitive appraisal of situations and links appropriate cortical sites together. It is then likely that different problems may arise when either network fails to initiate or function properly. PMID:20339549

  16. Anteroposterior dynamic balance reactions induced by circular translation of the visual field.

    PubMed

    Séverac Cauquil, A; Bessou, M; Dupui, P; Bessou, P

    1996-01-01

    The anteroposterior sway of subjects under conditions of spontaneous dynamic balance on a wobbly platform was measured during visual stimulation by a visual target executing a circular trajectory in the frontal plane. The target was either a component of the whole moving visual scene or moving on a stationary background. With the former stimulation, obtained through the use of rotating prismatic glasses, every point of the visual field appeared to describe a circular trajectory around its real position so that the whole visual field appeared to be circularly translated, undistorted, inducing a binocular pursuit movement. Under these conditions, stereotyped anteroposterior dynamic balance reactions synchronous with the position of the stimulus were elicited. The latter stimulation consisted of pursuing a luminous target describing a trajectory similar to that of the fixation point seen through the rotating prisms on the same, this time stable, visual background. Although pursuit eye movements were comparable, as demonstrated by electro-oculographic recordings, no stereotyped equilibration reaction was induced. It is concluded that the translatory motion of the background image on the retina in the latter experiments contributed to the body's stability as well as to the perception of a stable environment. PMID:8865085

  17. Spatial Scaling of the Profile of Selective Attention in the Visual Field.

    PubMed

    Gannon, Matthew A; Knapp, Ashley A; Adams, Thomas G; Long, Stephanie M; Parks, Nathan A

    2016-01-01

    Neural mechanisms of selective attention must be capable of adapting to variation in the absolute size of an attended stimulus in the ever-changing visual environment. To date, little is known regarding how attentional selection interacts with fluctuations in the spatial expanse of an attended object. Here, we use event-related potentials (ERPs) to investigate the scaling of attentional enhancement and suppression across the visual field. We measured ERPs while participants performed a task at fixation that varied in its attentional demands (attentional load) and visual angle (1.0° or 2.5°). Observers were presented with a stream of task-relevant stimuli while foveal, parafoveal, and peripheral visual locations were probed by irrelevant distractor stimuli. We found two important effects in the N1 component of visual ERPs. First, N1 modulations to task-relevant stimuli indexed attentional selection of stimuli during the load task and further correlated with task performance. Second, with increased task size, attentional modulation of the N1 to distractor stimuli showed a differential pattern that was consistent with a scaling of attentional selection. Together, these results demonstrate that the size of an attended stimulus scales the profile of attentional selection across the visual field and provides insights into the attentional mechanisms associated with such spatial scaling. PMID:27606426

  18. Visualization study on the static flow field around a straight-bladed vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Li, Yan; Tagawa, Kotaro

    2010-03-01

    Visual experiments based on the smoke wire way were carried out on a small model of Straight-blade Vertical Axis Wind Turbine (SB-VAWT) to invest the relationship between the static flow field characteristics and the rotor azimuth angle. The test rotor had 3 blades with NACA0018 aerofoil. The rotor diameter and blade chord were 0.3m and 0.07m, respectively. Visual photos of the static flow path lines in and around the rotor were obtained at every 5 degrees of the azimuth angle. Further, numerical computations of the static flow filed were also carried out for comparison with the same situation as the visual tests and the static torques at different azimuth angles were calculated. According to the results of visual tests and computations, the dependence of the starting performance on the azimuth angle was discussed. The solidity is an important factor affecting the starting performance of the SB-VAWT.

  19. Visualization study on the static flow field around a straight-bladed vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Li, Yan; Tagawa, Kotaro

    2009-12-01

    Visual experiments based on the smoke wire way were carried out on a small model of Straight-blade Vertical Axis Wind Turbine (SB-VAWT) to invest the relationship between the static flow field characteristics and the rotor azimuth angle. The test rotor had 3 blades with NACA0018 aerofoil. The rotor diameter and blade chord were 0.3m and 0.07m, respectively. Visual photos of the static flow path lines in and around the rotor were obtained at every 5 degrees of the azimuth angle. Further, numerical computations of the static flow filed were also carried out for comparison with the same situation as the visual tests and the static torques at different azimuth angles were calculated. According to the results of visual tests and computations, the dependence of the starting performance on the azimuth angle was discussed. The solidity is an important factor affecting the starting performance of the SB-VAWT.

  20. Multiresolution and Explicit Methods for Vector Field Analysis and Visualization

    NASA Technical Reports Server (NTRS)

    1996-01-01

    We first report on our current progress in the area of explicit methods for tangent curve computation. The basic idea of this method is to decompose the domain into a collection of triangles (or tetrahedra) and assume linear variation of the vector field over each cell. With this assumption, the equations which define a tangent curve become a system of linear, constant coefficient ODE's which can be solved explicitly. There are five different representation of the solution depending on the eigenvalues of the Jacobian. The analysis of these five cases is somewhat similar to the phase plane analysis often associate with critical point classification within the context of topological methods, but it is not exactly the same. There are some critical differences. Moving from one cell to the next as a tangent curve is tracked, requires the computation of the exit point which is an intersection of the solution of the constant coefficient ODE and the edge of a triangle. There are two possible approaches to this root computation problem. We can express the tangent curve into parametric form and substitute into an implicit form for the edge or we can express the edge in parametric form and substitute in an implicit form of the tangent curve. Normally the solution of a system of ODE's is given in parametric form and so the first approach is the most accessible and straightforward. The second approach requires the 'implicitization' of these parametric curves. The implicitization of parametric curves can often be rather difficult, but in this case we have been successful and have been able to develop algorithms and subsequent computer programs for both approaches. We will give these details along with some comparisons in a forthcoming research paper on this topic.

  1. Effect of Reference Scheme on Power and Phase of the Local Field Potential.

    PubMed

    Shirhatti, Vinay; Borthakur, Ayon; Ray, Supratim

    2016-05-01

    Brain signals are often analyzed in the spectral domain, where the power spectral density (PSD) and phase differences and consistency can reveal important information about the network. However, for proper interpretation, it is important to know whether these measures depend on stimulus/behavioral conditions or the reference scheme used to analyze data. We recorded local field potential (LFP) from an array of microelectrodes chronically implanted in area V1 of monkeys under different stimulus/behavioral conditions and computed PSD slopes, coherence, and phase difference between LFPs as a function of frequency and interelectrode distance while using four reference schemes: single wire, average, bipolar, and current source density. PSD slopes were dependent on reference scheme at low frequencies (below 200 Hz) but became invariant at higher frequencies. Average phase differences between sites also depended critically on referencing, switching from 0 degrees for single-wire to 180 degrees for average reference. Results were consistent across different stimulus/behavioral conditions. We were able to account for these results based on the coherence profile across sites and properties of the spectral estimator. Our results show that using different reference schemes can have drastic effects on phase differences and PSD slopes and therefore must be interpreted carefully to gain insights about network properties. PMID:26942748

  2. Parallax studies of four selected fields. [and their central and reference stars

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Gatewood, G. D.; Worek, T. F.

    1982-01-01

    Astrometric studies have been completed for four central stars Wolf 294, 39 Com, Case 2, and Vega - and selected reference stars in each of those regions. The parallax of Wolf 294 was measured as 0.1806 + or - 0.0033 arcsec. 39 Com is a visual/astrometric binary with an estimated period of 125 yr and a parallax of 0.0297 + or - 0.0044 arcsec. C 2 was measured as a white dwarf from a Warner and Swasey Observatory spectral survey; its white dwarf status is confirmed by its parallax of 0.0186 + or - 0.0109 arcsec. Vega's parallax was measured as 0.1243 + or - 0.0049 arcsec; a small apparent nonrandom distribution in the residuals is most likely an error from the neutral density filter used for magnitude reduction of the central star.

  3. A Novel Microscope for Visualizing Electric Fields in Organic Thin Film Devices Using Electric-Field-Induced Second-Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Karasuda, Tetushu; Kyomasu, Mikio

    2013-04-01

    We have developed a novel microscope for visualizing electric fields in organic thin film devices on the basis of electric-field-induced second-harmonic generation (EFISHG) measurement. By using a radial polarized laser beam as a probing light, we showed that the electric field formed in metal-C60-metal diodes in the film-thickness direction is visualized. The developed microscope has a potentiality in directly visualizing carrier motion in thin-film devices such as organic solar cells.

  4. Extraction of skin-friction fields from surface flow visualizations as an inverse problem

    NASA Astrophysics Data System (ADS)

    Liu, Tianshu

    2013-12-01

    Extraction of high-resolution skin-friction fields from surface flow visualization images as an inverse problem is discussed from a unified perspective. The surface flow visualizations used in this study are luminescent oil-film visualization and heat-transfer and mass-transfer visualizations with temperature- and pressure-sensitive paints (TSPs and PSPs). The theoretical foundations of these global methods are the thin-oil-film equation and the limiting forms of the energy- and mass-transport equations at a wall, which are projected onto the image plane to provide the relationships between a skin-friction field and the relevant quantities measured by using an imaging system. Since these equations can be re-cast in the same mathematical form as the optical flow equation, they can be solved by using the variational method in the image plane to extract relative or normalized skin-friction fields from images. Furthermore, in terms of instrumentation, essentially the same imaging system for measurements of luminescence can be used in these surface flow visualizations. Examples are given to demonstrate the applications of these methods in global skin-friction diagnostics of complex flows.

  5. A Case of Decreased Visual Field after Uneventful Cataract Surgery: Nonarteritic Anterior Ischemic Optic Neuropathy

    PubMed Central

    Lee, Hun; Kim, Chan Yun; Seong, Gong Je

    2010-01-01

    The purpose of this article is to report a case of nonarteritic anterior ischemic optic neuropathy (NAION) after uneventful cataract surgery. A 53-year-old Filipina underwent cataract surgery. She had a small optic disc with cup-to-disc ratio of 0.2 in the left eye and 0.3 in the right eye. On the first postoperative day, the uncorrected visual acuity (UCVA) was 20/20, with an intraocular pressure (IOP) of 20 mmHg in the left eye. At one week after operation, the UCVA was 20/20 and the IOP was 15 mmHg. Three weeks later, she underwent cataract surgery in the right eye. On the first postoperative day, her UCVA was 20/20 in both eyes, but she complained of a visual field decrease in the left eye. A relative afferent pupillary defect (RAPD) was noted and the optic disc was pallid and swollen diffusely. A red-free photo showed defect surrounding the optic disc. A visual field test showed tunnel vision sparing the central vision. In this report, the authors hypothesize an association between cataract extraction and delayed NAION. Since the risk of NAION in the fellow eye is 30-50%, visual acuity, visual field, fundus exam and RAPD should be routinely checked. PMID:20157417

  6. The representation of the ipsilateral visual field in human cerebral cortex

    PubMed Central

    Tootell, Roger B. H.; Mendola, Janine D.; Hadjikhani, Nouchine K.; Liu, Arthur K.; Dale, Anders M.

    1998-01-01

    Previous studies of cortical retinotopy focused on influences from the contralateral visual field, because ascending inputs to cortex are known to be crossed. Here, functional magnetic resonance imaging was used to demonstrate and analyze an ipsilateral representation in human visual cortex. Moving stimuli, in a range of ipsilateral visual field locations, revealed activity: (i) along the vertical meridian in retinotopic (presumably lower-tier) areas; and (ii) in two large branches anterior to that, in presumptive higher-tier areas. One branch shares the anterior vertical meridian representation in human V3A, extending superiorly toward parietal cortex. The second branch runs antero-posteriorly along lateral visual cortex, overlying motion-selective area MT. Ipsilateral stimuli sparing the region around the vertical meridian representation also produced signal reductions (perhaps reflecting neural inhibition) in areas showing contralaterally driven retinotopy. Systematic sampling across a range of ipsilateral visual field extents revealed significant increases in ipsilateral activation in V3A and V4v, compared with immediately posterior areas V3 and VP. Finally, comparisons between ipsilateral stimuli of different types but equal retinotopic extent showed clear stimulus specificity, consistent with earlier suggestions of a functional segregation of motion vs. form processing in parietal vs. temporal cortex, respectively. PMID:9448246

  7. A case of decreased visual field after uneventful cataract surgery: nonarteritic anterior ischemic optic neuropathy.

    PubMed

    Lee, Hun; Kim, Chan Yun; Seong, Gong Je; Ma, Kyoung Tak

    2010-02-01

    The purpose of this article is to report a case of nonarteritic anterior ischemic optic neuropathy (NAION) after uneventful cataract surgery. A 53-year-old Filipina underwent cataract surgery. She had a small optic disc with cup-to-disc ratio of 0.2 in the left eye and 0.3 in the right eye. On the first postoperative day, the uncorrected visual acuity (UCVA) was 20/20, with an intraocular pressure (IOP) of 20 mmHg in the left eye. At one week after operation, the UCVA was 20/20 and the IOP was 15 mmHg. Three weeks later, she underwent cataract surgery in the right eye. On the first postoperative day, her UCVA was 20/20 in both eyes, but she complained of a visual field decrease in the left eye. A relative afferent pupillary defect (RAPD) was noted and the optic disc was pallid and swollen diffusely. A red-free photo showed defect surrounding the optic disc. A visual field test showed tunnel vision sparing the central vision. In this report, the authors hypothesize an association between cataract extraction and delayed NAION. Since the risk of NAION in the fellow eye is 30-50%, visual acuity, visual field, fundus exam and RAPD should be routinely checked. PMID:20157417

  8. Locus of information in words and the right visual field effect.

    PubMed

    Bryden, M P; Mondor, T A; Loken, M; Ingleton, M A; Bergstrom, K

    1990-09-01

    The right visual field (RVF) advantage found for the identification or classification of words has usually been interpreted as evidence for left hemisphere language functions. It has more recently been explained as the result of the fact that the most informative part of the word, presumably the beginning, is in a region of better visual acuity. It is not clear from existing evidence that the beginnings of words are in fact more informative. The present study assessed the locus of information in words by deleting either the initial or terminal one or two letters. Subjects were required to generate a completion. Regardless of whether subjects were scored as correct for generating the original target word (as would be appropriate in a naming study) or for producing any legitimate word (as would be appropriate for a lexical decision study), the results indicated that most words have more information in the initial letters. Nevertheless, there are exceptions to this rule, and some words have more terminal information. Equal numbers of words with more initial information and with more terminal information were selected for two visual field studies in order to assess the effect of the locus of information on visual laterality. In neither a lexical decision study nor a naming study did locus of information affect the commonly observed right visual field superiority. Thus the distribution of information is not likely to be a major confounding variable in laterality studies employing horizontally presented words. PMID:2223044

  9. Implications of X-ray tube parameter deviations in X-ray reference fields.

    PubMed

    Behnke, B; Hupe, O; Ambrosi, P

    2016-02-01

    For the purpose of radiation protection, ICRU Report 57/ICRP Publication 74 provides a list of monoenergetic conversion coefficients to be used with, among others, photon reference fields generated with X-ray tubes. A comprehensive definition of these photon reference fields can be found in international standard ISO 4037; however, it lacks thorough indication of the allowed deviations of essential parameters that influence these X-ray reference fields. These parameters are the high-voltage tube potential, the thickness of the beryllium window and the purity and thickness of the filter materials used to create different radiation qualities. Small variations of these parameters can lead to significant changes in the created X-ray spectra and, hence, the spectra-dependent conversion coefficients for phantom-related radiation-protection quantities. This can lead to situations in which the conversion coefficients listed in ISO 4037 cannot be used, resulting in time-consuming spectrometry measurements. In this work, the impact on the resulting conversion coefficients is investigated using a simplified mathematical approximation model. The findings are validated with an independent X-ray spectra calculation programme. As a result, well-founded upper limit values on the allowed deviations of the essential X-ray tube parameters are proposed to be used in a future revision of ISO 4037. PMID:25889609

  10. Two visual areas located in the middle suprasylvian gyrus (cytoarchitectonic field 7) of the cat's cortex.

    PubMed

    Pigarev, I N; Rodionova, E I

    1998-08-01

    Neuronal properties and topographic organization of the middle suprasylvian gyrus (cortical cytoarchitectonic field 7) were studied in three behaving cats with painlessly fixed heads. Two main neuronal types were found within this field. Type 1 neurons occupied the lateral part of the field and bordered representation of directionally selective neurons of the lateral suprasylvian visual area by vertical retinal meridian. Type 1 neurons had elongated and radially oriented receptive fields located in the lower part of contralateral visual field. Type 1 neurons preferred stimuli moving out or to the centre of gaze at a low or moderate speed, and many of them were depth selective. The responses were enhanced by attention, oriented to the presented stimulus. Medial part of the field 7 along the border with the area V3 was occupied by neurons with not elongated receptive fields (type 2). These neurons preferred moderate and high speeds of motion, and gratings of proper spatial frequency and orientation were effective stimuli for them. Border between representations of type 2 and type 1 neurons coincided with projection of horizontal retinal meridian. At the rostral and caudal borders of the field 7 abrupt changes of neuronal properties took place. Neurons which abutted field 7 anteriorly and posteriorly resembled hypercomplex cells and their small receptive fields were located in the central part of the visual field. Topographical considerations and receptive field properties allowed us to conclude that the medial part of the field 7 (included type 2 neurons) is functionally equivalent to the area V4 in the cortex of primates, while the lateral part (type 1 neurons) may correspond to the area V4T. PMID:9639267